Merge commit '9614911dca3f53cbdc6df842d273d84c9c7d025f' as 'solution/H07'

solution/H07/.editorconfig

@@ -0,0 +1,12 @@
+# Editor configuration, see https://editorconfig.org
+
+[*]
+charset = utf-8
+end_of_line = lf
+indent_style = space
+indent_size = 4
+insert_final_newline = true
+trim_trailing_whitespace = true
+
+[{*.yml,*.json}]
+indent_size = 2

solution/H07/.gitignore

@@ -0,0 +1,88 @@
+### Intellij ###
+.idea/
+*.iws
+/out/
+*.iml
+.idea_modules/
+atlassian-ide-plugin.xml
+
+### VS-Code ###
+.vscode/
+.VSCodeCounter/
+
+### Eclipse ###
+.metadata
+bin/
+tmp/
+*.tmp
+*.bak
+*.swp
+*~.nib
+local.properties
+.settings/
+.loadpath
+.recommenders
+.externalToolBuilders/
+*.launch
+.factorypath
+.recommenders/
+.apt_generated/
+.project
+.classpath
+
+### Linux ###
+*~
+.fuse_hidden*
+.directory
+.Trash-*
+.nfs*
+
+### macOS ###
+.DS_Store
+.AppleDouble
+.LSOverride
+Icon
+._*
+.DocumentRevisions-V100
+.fseventsd
+.Spotlight-V100
+.TemporaryItems
+.Trashes
+.VolumeIcon.icns
+.com.apple.timemachine.donotpresent
+.AppleDB
+.AppleDesktop
+Network Trash Folder
+Temporary Items
+.apdisk
+
+### NetBeans ###
+nbproject/private/
+build/
+nbbuild/
+dist/
+nbdist/
+.nb-gradle/
+
+### Windows ###
+# Windows thumbnail cache files
+Thumbs.db
+ehthumbs.db
+ehthumbs_vista.db
+*.stackdump
+[Dd]esktop.ini
+$RECYCLE.BIN/
+*.lnk
+
+### Gradle ###
+.gradle
+/build/
+out/
+gradle-app.setting
+!gradle-wrapper.jar
+.gradletasknamecache
+
+*.hprof
+screenshots/
+
+jagr.conf

solution/H07/README.md

@@ -0,0 +1,4 @@
+# Musterlösung zu Hausübung 07
+
+Beachten Sie die Hinweise zum Herunterladen, Importieren, Bearbeitern, Exportieren und Hochladen in unserem
+[Studierenden-Guide](https://wiki.tudalgo.org/)

solution/H07/build.gradle.kts

@@ -0,0 +1,46 @@
+plugins {
+    alias(libs.plugins.algomate)
+    alias(libs.plugins.style)
+}
+
+version = file("version").readLines().first()
+
+exercise {
+    assignmentId.set("h07")
+}
+
+submission {
+    // ACHTUNG!
+    // Setzen Sie im folgenden Bereich Ihre TU-ID (NICHT Ihre Matrikelnummer!), Ihren Nachnamen und Ihren Vornamen
+    // in Anführungszeichen (z.B. "ab12cdef" für Ihre TU-ID) ein!
+    // BEISPIEL:
+    // studentId = "ab12cdef"
+    // firstName = "sol_first"
+    // lastName = "sol_last"
+    studentId = "ab12cdef"
+    firstName = "sol_first"
+    lastName = "sol_last"
+
+    // Optionally require own tests for mainBuildSubmission task. Default is false
+    requireTests = false
+}
+
+jagr {
+    graders {
+        val graderPublic by getting
+        val graderPrivate by creating {
+            parent(graderPublic)
+            graderName.set("FOP-2425-H07-Private")
+            rubricProviderName.set("h07.H07_RubricProvider")
+        }
+    }
+    graders {
+        val graderPrivate by creating {
+            graderName.set("H07-Private")
+            rubricProviderName.set("h07.H07_RubricProvider")
+            configureDependencies {
+                implementation(libs.algoutils.tutor)
+            }
+        }
+    }
+}

solution/H07/gradle/libs.versions.toml

@@ -0,0 +1,3 @@
+[plugins]
+algomate = { id = "org.tudalgo.algomate", version = "0.7.1" }
+style = { id = "org.sourcegrade.style", version = "3.0.0" }

solution/H07/gradle/wrapper/gradle-wrapper.properties

@@ -0,0 +1,6 @@
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.10.2-all.zip
+networkTimeout=10000
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists

solution/H07/gradlew

@@ -0,0 +1,245 @@
+#!/bin/sh
+
+#
+# Copyright © 2015-2021 the original authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+##############################################################################
+#
+#   Gradle start up script for POSIX generated by Gradle.
+#
+#   Important for running:
+#
+#   (1) You need a POSIX-compliant shell to run this script. If your /bin/sh is
+#       noncompliant, but you have some other compliant shell such as ksh or
+#       bash, then to run this script, type that shell name before the whole
+#       command line, like:
+#
+#           ksh Gradle
+#
+#       Busybox and similar reduced shells will NOT work, because this script
+#       requires all of these POSIX shell features:
+#         * functions;
+#         * expansions «$var», «${var}», «${var:-default}», «${var+SET}»,
+#           «${var#prefix}», «${var%suffix}», and «$( cmd )»;
+#         * compound commands having a testable exit status, especially «case»;
+#         * various built-in commands including «command», «set», and «ulimit».
+#
+#   Important for patching:
+#
+#   (2) This script targets any POSIX shell, so it avoids extensions provided
+#       by Bash, Ksh, etc; in particular arrays are avoided.
+#
+#       The "traditional" practice of packing multiple parameters into a
+#       space-separated string is a well documented source of bugs and security
+#       problems, so this is (mostly) avoided, by progressively accumulating
+#       options in "$@", and eventually passing that to Java.
+#
+#       Where the inherited environment variables (DEFAULT_JVM_OPTS, JAVA_OPTS,
+#       and GRADLE_OPTS) rely on word-splitting, this is performed explicitly;
+#       see the in-line comments for details.
+#
+#       There are tweaks for specific operating systems such as AIX, CygWin,
+#       Darwin, MinGW, and NonStop.
+#
+#   (3) This script is generated from the Groovy template
+#       https://github.com/gradle/gradle/blob/HEAD/subprojects/plugins/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
+#       within the Gradle project.
+#
+#       You can find Gradle at https://github.com/gradle/gradle/.
+#
+##############################################################################
+
+# Attempt to set APP_HOME
+
+# Resolve links: $0 may be a link
+app_path=$0
+
+# Need this for daisy-chained symlinks.
+while
+    APP_HOME=${app_path%"${app_path##*/}"}  # leaves a trailing /; empty if no leading path
+    [ -h "$app_path" ]
+do
+    ls=$( ls -ld "$app_path" )
+    link=${ls#*' -> '}
+    case $link in             #(
+      /*)   app_path=$link ;; #(
+      *)    app_path=$APP_HOME$link ;;
+    esac
+done
+
+# This is normally unused
+# shellcheck disable=SC2034
+APP_BASE_NAME=${0##*/}
+APP_HOME=$( cd "${APP_HOME:-./}" && pwd -P ) || exit
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD=maximum
+
+warn () {
+    echo "$*"
+} >&2
+
+die () {
+    echo
+    echo "$*"
+    echo
+    exit 1
+} >&2
+
+# OS specific support (must be 'true' or 'false').
+cygwin=false
+msys=false
+darwin=false
+nonstop=false
+case "$( uname )" in                #(
+  CYGWIN* )         cygwin=true  ;; #(
+  Darwin* )         darwin=true  ;; #(
+  MSYS* | MINGW* )  msys=true    ;; #(
+  NONSTOP* )        nonstop=true ;;
+esac
+
+CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
+
+
+# Determine the Java command to use to start the JVM.
+if [ -n "$JAVA_HOME" ] ; then
+    if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
+        # IBM's JDK on AIX uses strange locations for the executables
+        JAVACMD=$JAVA_HOME/jre/sh/java
+    else
+        JAVACMD=$JAVA_HOME/bin/java
+    fi
+    if [ ! -x "$JAVACMD" ] ; then
+        die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+else
+    JAVACMD=java
+    which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+fi
+
+# Increase the maximum file descriptors if we can.
+if ! "$cygwin" && ! "$darwin" && ! "$nonstop" ; then
+    case $MAX_FD in #(
+      max*)
+        # In POSIX sh, ulimit -H is undefined. That's why the result is checked to see if it worked.
+        # shellcheck disable=SC3045
+        MAX_FD=$( ulimit -H -n ) ||
+            warn "Could not query maximum file descriptor limit"
+    esac
+    case $MAX_FD in  #(
+      '' | soft) :;; #(
+      *)
+        # In POSIX sh, ulimit -n is undefined. That's why the result is checked to see if it worked.
+        # shellcheck disable=SC3045
+        ulimit -n "$MAX_FD" ||
+            warn "Could not set maximum file descriptor limit to $MAX_FD"
+    esac
+fi
+
+# Collect all arguments for the java command, stacking in reverse order:
+#   * args from the command line
+#   * the main class name
+#   * -classpath
+#   * -D...appname settings
+#   * --module-path (only if needed)
+#   * DEFAULT_JVM_OPTS, JAVA_OPTS, and GRADLE_OPTS environment variables.
+
+# For Cygwin or MSYS, switch paths to Windows format before running java
+if "$cygwin" || "$msys" ; then
+    APP_HOME=$( cygpath --path --mixed "$APP_HOME" )
+    CLASSPATH=$( cygpath --path --mixed "$CLASSPATH" )
+
+    JAVACMD=$( cygpath --unix "$JAVACMD" )
+
+    # Now convert the arguments - kludge to limit ourselves to /bin/sh
+    for arg do
+        if
+            case $arg in                                #(
+              -*)   false ;;                            # don't mess with options #(
+              /?*)  t=${arg#/} t=/${t%%/*}              # looks like a POSIX filepath
+                    [ -e "$t" ] ;;                      #(
+              *)    false ;;
+            esac
+        then
+            arg=$( cygpath --path --ignore --mixed "$arg" )
+        fi
+        # Roll the args list around exactly as many times as the number of
+        # args, so each arg winds up back in the position where it started, but
+        # possibly modified.
+        #
+        # NB: a `for` loop captures its iteration list before it begins, so
+        # changing the positional parameters here affects neither the number of
+        # iterations, nor the values presented in `arg`.
+        shift                   # remove old arg
+        set -- "$@" "$arg"      # push replacement arg
+    done
+fi
+
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
+
+# Collect all arguments for the java command;
+#   * $DEFAULT_JVM_OPTS, $JAVA_OPTS, and $GRADLE_OPTS can contain fragments of
+#     shell script including quotes and variable substitutions, so put them in
+#     double quotes to make sure that they get re-expanded; and
+#   * put everything else in single quotes, so that it's not re-expanded.
+
+set -- \
+        "-Dorg.gradle.appname=$APP_BASE_NAME" \
+        -classpath "$CLASSPATH" \
+        org.gradle.wrapper.GradleWrapperMain \
+        "$@"
+
+# Stop when "xargs" is not available.
+if ! command -v xargs >/dev/null 2>&1
+then
+    die "xargs is not available"
+fi
+
+# Use "xargs" to parse quoted args.
+#
+# With -n1 it outputs one arg per line, with the quotes and backslashes removed.
+#
+# In Bash we could simply go:
+#
+#   readarray ARGS < <( xargs -n1 <<<"$var" ) &&
+#   set -- "${ARGS[@]}" "$@"
+#
+# but POSIX shell has neither arrays nor command substitution, so instead we
+# post-process each arg (as a line of input to sed) to backslash-escape any
+# character that might be a shell metacharacter, then use eval to reverse
+# that process (while maintaining the separation between arguments), and wrap
+# the whole thing up as a single "set" statement.
+#
+# This will of course break if any of these variables contains a newline or
+# an unmatched quote.
+#
+
+eval "set -- $(
+        printf '%s\n' "$DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS" |
+        xargs -n1 |
+        sed ' s~[^-[:alnum:]+,./:=@_]~\\&~g; ' |
+        tr '\n' ' '
+    )" '"$@"'
+
+exec "$JAVACMD" "$@"

solution/H07/gradlew.bat

@@ -0,0 +1,92 @@
+@rem
+@rem Copyright 2015 the original author or authors.
+@rem
+@rem Licensed under the Apache License, Version 2.0 (the "License");
+@rem you may not use this file except in compliance with the License.
+@rem You may obtain a copy of the License at
+@rem
+@rem      https://www.apache.org/licenses/LICENSE-2.0
+@rem
+@rem Unless required by applicable law or agreed to in writing, software
+@rem distributed under the License is distributed on an "AS IS" BASIS,
+@rem WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+@rem See the License for the specific language governing permissions and
+@rem limitations under the License.
+@rem
+
+@if "%DEBUG%"=="" @echo off
+@rem ##########################################################################
+@rem
+@rem  Gradle startup script for Windows
+@rem
+@rem ##########################################################################
+
+@rem Set local scope for the variables with windows NT shell
+if "%OS%"=="Windows_NT" setlocal
+
+set DIRNAME=%~dp0
+if "%DIRNAME%"=="" set DIRNAME=.
+@rem This is normally unused
+set APP_BASE_NAME=%~n0
+set APP_HOME=%DIRNAME%
+
+@rem Resolve any "." and ".." in APP_HOME to make it shorter.
+for %%i in ("%APP_HOME%") do set APP_HOME=%%~fi
+
+@rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+set DEFAULT_JVM_OPTS="-Xmx64m" "-Xms64m"
+
+@rem Find java.exe
+if defined JAVA_HOME goto findJavaFromJavaHome
+
+set JAVA_EXE=java.exe
+%JAVA_EXE% -version >NUL 2>&1
+if %ERRORLEVEL% equ 0 goto execute
+
+echo.
+echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:findJavaFromJavaHome
+set JAVA_HOME=%JAVA_HOME:"=%
+set JAVA_EXE=%JAVA_HOME%/bin/java.exe
+
+if exist "%JAVA_EXE%" goto execute
+
+echo.
+echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME%
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:execute
+@rem Setup the command line
+
+set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
+
+
+@rem Execute Gradle
+"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %*
+
+:end
+@rem End local scope for the variables with windows NT shell
+if %ERRORLEVEL% equ 0 goto mainEnd
+
+:fail
+rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of
+rem the _cmd.exe /c_ return code!
+set EXIT_CODE=%ERRORLEVEL%
+if %EXIT_CODE% equ 0 set EXIT_CODE=1
+if not ""=="%GRADLE_EXIT_CONSOLE%" exit %EXIT_CODE%
+exit /b %EXIT_CODE%
+
+:mainEnd
+if "%OS%"=="Windows_NT" endlocal
+
+:omega

solution/H07/settings.gradle.kts

@@ -0,0 +1,11 @@
+dependencyResolutionManagement {
+    repositoriesMode.set(RepositoriesMode.FAIL_ON_PROJECT_REPOS)
+    repositories {
+//        mavenLocal()
+        maven("https://s01.oss.sonatype.org/content/repositories/snapshots")
+        maven("https://jitpack.io")
+        mavenCentral()
+    }
+}
+
+rootProject.name = "H07-Root"

solution/H07/src/graderPrivate/java/h07/ArithmeticExpressionTest.java

@@ -0,0 +1,25 @@
+package h07;
+
+import org.junit.jupiter.api.Test;
+import org.sourcegrade.jagr.api.rubric.TestForSubmission;
+
+@TestForSubmission
+public class ArithmeticExpressionTest {
+
+    @Test
+    public void testDefinition() {
+        ClassReference.ARITHMETIC_EXPRESSION.assertCorrectlyDefined();
+        MethodReference.ARITHMETIC_EXPRESSION_EVALUATE.assertCorrectlyDefined();
+    }
+
+    @Test
+    public void testNaming() {
+        ClassReference.ARITHMETIC_EXPRESSION.assertNamedCorrectly();
+        MethodReference.ARITHMETIC_EXPRESSION_EVALUATE.assertNamedCorrectly();
+    }
+
+    @Test
+    public void testPackage() {
+        ClassReference.ARITHMETIC_EXPRESSION.assertDefinedInCorrectPackage();
+    }
+}

solution/H07/src/graderPrivate/java/h07/ClassReference.java

@@ -0,0 +1,187 @@
+package h07;
+
+import org.tudalgo.algoutils.tutor.general.assertions.Context;
+import org.tudalgo.algoutils.tutor.general.reflections.BasicPackageLink;
+import org.tudalgo.algoutils.tutor.general.reflections.BasicTypeLink;
+import org.tudalgo.algoutils.tutor.general.reflections.Link;
+import org.tudalgo.algoutils.tutor.general.reflections.Modifier;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+
+import static org.tudalgo.algoutils.tutor.general.assertions.Assertions2.*;
+
+
+public class ClassReference {
+
+    public static final List<String> PREDEFINED_PACKAGES = List.of("h07", "h07.Peano", "h07.peano");
+
+    public static final ClassReference NUMBER_EXPRESSION = new ClassReference("h07", "NumberExpression", Link.Kind.INTERFACE);
+    public static final ClassReference PEANO_NUMBER_EXPRESSION =
+        new ClassReference("h07.peano", "PeanoNumberExpression", Link.Kind.INTERFACE);
+    public static final ClassReference ARITHMETIC_EXPRESSION =
+        new ClassReference("h07", "ArithmeticExpression", Link.Kind.INTERFACE);
+    public static final ClassReference PEANO_ARITHMETIC_EXPRESSION =
+        new ClassReference("h07.peano", "PeanoArithmeticExpression", Link.Kind.INTERFACE);
+    public static final ClassReference PEANO_ADD_EXPRESSION = new ClassReference("h07.peano",
+        "PeanoAddExpression",
+        Link.Kind.CLASS,
+        new BasicTypeLink[] {PEANO_ARITHMETIC_EXPRESSION.link},
+        Modifier.PUBLIC,
+        Modifier.NON_FINAL
+    );
+    public static final ClassReference PEANO_MULTIPLY_EXPRESSION = new ClassReference("h07.peano",
+        "PeanoMultiplyExpression",
+        Link.Kind.CLASS,
+        new BasicTypeLink[] {PEANO_ARITHMETIC_EXPRESSION.link},
+        Modifier.PUBLIC,
+        Modifier.NON_FINAL
+    );
+    public static final ClassReference CONVERT_NUMBER_TO_PEANO_EXPRESSION =
+        new ClassReference("h07", "ConvertNumberToPeanoExpression", Link.Kind.INTERFACE);
+    public static final ClassReference CONVERT_PEANO_TO_NUMBER_EXPRESSION =
+        new ClassReference("h07", "ConvertPeanoToNumberExpression", Link.Kind.INTERFACE);
+    public static final ClassReference CONVERT_NUMBER_TO_PEANO_EXPRESSION_IMPL = new ClassReference("h07",
+        "ConvertNumberToPeanoExpressionImpl",
+        Link.Kind.CLASS,
+        new BasicTypeLink[] {CONVERT_NUMBER_TO_PEANO_EXPRESSION.link},
+        Modifier.PUBLIC,
+        Modifier.NON_FINAL
+    );
+    public static final ClassReference CONVERT_PEANO_TO_NUMBER_EXPRESSION_IMPL = new ClassReference("h07",
+        "ConvertPeanoToNumberExpressionImpl",
+        Link.Kind.CLASS,
+        new BasicTypeLink[] {CONVERT_PEANO_TO_NUMBER_EXPRESSION.link},
+        Modifier.PUBLIC,
+        Modifier.NON_FINAL
+    );
+
+    public static final ClassReference ZERO = new ClassReference("h07.peano",
+        "Zero",
+        Link.Kind.CLASS
+    );
+
+    public static final ClassReference SUCCESSOR = new ClassReference("h07.peano",
+        "Successor",
+        Link.Kind.CLASS
+    );
+
+    public static final ClassReference NATURAL_NUMBER = new ClassReference("h07.peano",
+        "NaturalNumber",
+        Link.Kind.CLASS
+    );
+
+    public static final ClassReference PEANO_NUMBER_EXPRESSION_FACTORY = new ClassReference("h07.peano",
+        "PeanoNumberExpressionFactory",
+        Link.Kind.CLASS
+    );
+
+    private final String pack;
+    private final String name;
+    private final Link.Kind kind;
+    private final BasicTypeLink[] superClasses;
+    private final Modifier[] modifiers;
+    private BasicTypeLink link;
+
+    public ClassReference(String pack, String name, Link.Kind kind, BasicTypeLink... superClasses) {
+        this(pack, name, kind, superClasses, new Modifier[0]);
+    }
+
+    public ClassReference(String pack, String name, Link.Kind kind, BasicTypeLink[] superClasses,
+                          Modifier... modifiers) {
+        this.pack = pack;
+        this.name = name;
+        this.kind = kind;
+        this.superClasses = superClasses;
+        this.modifiers = modifiers;
+
+        try {
+            for (String packageName : PREDEFINED_PACKAGES) {
+                link = (BasicTypeLink) BasicPackageLink.of(packageName).getType(Tests.stringMatcher(name));
+                if (link != null && !link.reflection().getName().endsWith("Test")) {
+                    return;
+                }
+            }
+            link = null;
+
+        } catch (Exception ignored) {
+        }
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public boolean isDefined() {
+        return link != null;
+    }
+
+    public void assertDefined() {
+        assertTrue(
+            isDefined(),
+            emptyContext(),
+            r -> String.format("Could not find Type %s. Type is not defined or could not be found.", name)
+        );
+    }
+
+    public void assertCorrectlyDefined() {
+        assertDefined();
+        Context context = contextBuilder()
+            .add("expected package", pack)
+            .add("expected kind", kind)
+            .add("expected name", name)
+            .add("expected modifier", Arrays.stream(modifiers).map(Modifier::keyword).collect(Collectors.joining(", ")))
+            .add("package", link.reflection().getPackage().getName())
+            .add("kind", link.kind())
+            .add("name", link.name())
+            .build();
+
+        assertNotNull(link, context, r -> "Could not find class %s.".formatted(name));
+        assertEquals(kind, link.kind(), context, r -> "Kind does not match expected kind.");
+        assertTrue(
+            Arrays.stream(modifiers).allMatch(m -> m.is(link.modifiers())),
+            context,
+            r -> "The modifiers of the type do not match the expected modifiers."
+        );
+    }
+
+    public void assertNamedCorrectly() {
+        if (!isDefined()) {
+            return;
+        }
+        Context context = contextBuilder()
+            .add("expected name", name)
+            .add("name", link.name())
+            .build();
+
+        assertNotNull(link, context, r -> "Could not find class %s.".formatted(name));
+        assertEquals(name, link.name(), context, r -> "The name of the Type does not match the expected name.");
+    }
+
+    public void assertDefinedInCorrectPackage() {
+        assertDefined();
+        Context context = contextBuilder()
+            .add("expected package", pack)
+            .add("expected kind", kind)
+            .add("expected name", name)
+            .add("expected modifier", Arrays.stream(modifiers).map(Modifier::keyword).collect(Collectors.joining(", ")))
+            .add("package", link.reflection().getPackage().getName())
+            .add("kind", link.kind())
+            .add("name", link.name())
+            .build();
+
+        assertNotNull(link, context, r -> "Could not find class %s.".formatted(name));
+        assertEquals(
+            pack.toLowerCase(),
+            link.reflection().getPackage().getName().toLowerCase(),
+            context,
+            r -> "Package name does not match expected package name."
+        );
+    }
+
+    public BasicTypeLink getLink() {
+        assertDefined();
+        return link;
+    }
+}

solution/H07/src/graderPrivate/java/h07/ConvertNumberToPeanoExpressionImplTest.java

@@ -0,0 +1,92 @@
+package h07;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.sourcegrade.jagr.api.rubric.TestForSubmission;
+import org.tudalgo.algoutils.tutor.general.assertions.Assertions2;
+import org.tudalgo.algoutils.tutor.general.assertions.Context;
+import org.tudalgo.algoutils.tutor.general.json.JsonParameterSet;
+import org.tudalgo.algoutils.tutor.general.json.JsonParameterSetTest;
+import org.tudalgo.algoutils.tutor.general.reflections.BasicMethodLink;
+import spoon.reflect.code.CtLambda;
+import spoon.reflect.declaration.CtMethod;
+
+import java.util.List;
+
+import static h07.ClassReference.CONVERT_NUMBER_TO_PEANO_EXPRESSION_IMPL;
+import static h07.ClassReference.NUMBER_EXPRESSION;
+import static h07.H07Test.getCtElements;
+import static h07.MethodReference.CONVERT_NUMBER_TO_PEANO_EXPRESSION_CONVERT;
+import static h07.MethodReference.PEANO_NUMBER_EXPRESSION_EVALUATE;
+import static org.mockito.Mockito.CALLS_REAL_METHODS;
+import static org.mockito.Mockito.mock;
+import static org.tudalgo.algoutils.tutor.general.assertions.Assertions2.assertEquals;
+import static org.tudalgo.algoutils.tutor.general.assertions.Assertions2.contextBuilder;
+
+@TestForSubmission
+public class ConvertNumberToPeanoExpressionImplTest {
+
+    @Test
+    public void testDefinition() {
+        CONVERT_NUMBER_TO_PEANO_EXPRESSION_IMPL.assertCorrectlyDefined();
+    }
+
+    @Test
+    public void testNaming() {
+        CONVERT_NUMBER_TO_PEANO_EXPRESSION_IMPL.assertNamedCorrectly();
+    }
+
+    @Test
+    public void testPackage() {
+        CONVERT_NUMBER_TO_PEANO_EXPRESSION_IMPL.assertDefinedInCorrectPackage();
+    }
+
+    @ParameterizedTest
+    @JsonParameterSetTest(value = "ConvertNumberToPeanoExpressionImpl_X.json")
+    public void testEvaluate_X(JsonParameterSet params) throws Throwable {
+        performTest(params);
+    }
+
+    @ParameterizedTest
+    @JsonParameterSetTest(value = "ConvertNumberToPeanoExpressionImpl_0.json")
+    public void testEvaluate_0(JsonParameterSet params) throws Throwable {
+        performTest(params);
+    }
+
+    private static void performTest(JsonParameterSet params) throws Throwable {
+        int x = params.getInt("x");
+
+        Object numberExpression = NumberConverter.toNumberExpression(x);
+
+        Object mock = mock(CONVERT_NUMBER_TO_PEANO_EXPRESSION_IMPL.getLink().reflection(), CALLS_REAL_METHODS);
+        Object returned = CONVERT_NUMBER_TO_PEANO_EXPRESSION_CONVERT.invoke(mock.getClass(), mock, numberExpression);
+
+        Object actualPeano = PEANO_NUMBER_EXPRESSION_EVALUATE.invoke(returned.getClass(), returned);
+
+        int actual = NumberConverter.toNaturalNumber(actualPeano);
+
+        assertEquals(x, actual, params.toContext(), r -> "Value returned by convert() does not match expected.");
+    }
+
+    @Test
+    public void testConvertRequirements() {
+        CtMethod<?> evaluate =
+            ((BasicMethodLink) CONVERT_NUMBER_TO_PEANO_EXPRESSION_CONVERT.getLink(
+                CONVERT_NUMBER_TO_PEANO_EXPRESSION_IMPL.getLink().reflection(),
+                NUMBER_EXPRESSION.getLink().reflection()
+            )).getCtElement();
+
+        getCtElements(List.of(CONVERT_NUMBER_TO_PEANO_EXPRESSION_IMPL.getLink().reflection()), CtLambda.class, evaluate)
+            .forEach(ctLambda -> {
+                    String body = ctLambda.toStringDebug();
+                    Context context = contextBuilder().add("Lambda", body).build();
+
+                    Assertions2.assertNull(
+                        ctLambda.getBody(),
+                        context,
+                        r -> "convert() does not use correct lambdas."
+                    );
+                }
+            );
+    }
+}

solution/H07/src/graderPrivate/java/h07/ConvertNumberToPeanoExpressionTest.java

@@ -0,0 +1,25 @@
+package h07;
+
+import org.junit.jupiter.api.Test;
+import org.sourcegrade.jagr.api.rubric.TestForSubmission;
+
+@TestForSubmission
+public class ConvertNumberToPeanoExpressionTest {
+
+    @Test
+    public void testDefinition() {
+        ClassReference.CONVERT_NUMBER_TO_PEANO_EXPRESSION.assertCorrectlyDefined();
+        MethodReference.CONVERT_NUMBER_TO_PEANO_EXPRESSION_CONVERT.assertCorrectlyDefined();
+    }
+
+    @Test
+    public void testNaming() {
+        ClassReference.CONVERT_NUMBER_TO_PEANO_EXPRESSION.assertNamedCorrectly();
+        MethodReference.CONVERT_NUMBER_TO_PEANO_EXPRESSION_CONVERT.assertNamedCorrectly();
+    }
+
+    @Test
+    public void testPackage() {
+        ClassReference.CONVERT_NUMBER_TO_PEANO_EXPRESSION.assertDefinedInCorrectPackage();
+    }
+}

solution/H07/src/graderPrivate/java/h07/ConvertPeanoToNumberExpressionImplTest.java

@@ -0,0 +1,96 @@
+package h07;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.sourcegrade.jagr.api.rubric.TestForSubmission;
+import org.tudalgo.algoutils.tutor.general.assertions.Assertions2;
+import org.tudalgo.algoutils.tutor.general.assertions.Context;
+import org.tudalgo.algoutils.tutor.general.json.JsonParameterSet;
+import org.tudalgo.algoutils.tutor.general.json.JsonParameterSetTest;
+import org.tudalgo.algoutils.tutor.general.reflections.BasicMethodLink;
+import spoon.reflect.code.CtLambda;
+import spoon.reflect.declaration.CtMethod;
+
+import java.util.List;
+
+import static h07.ClassReference.CONVERT_PEANO_TO_NUMBER_EXPRESSION_IMPL;
+import static h07.ClassReference.PEANO_NUMBER_EXPRESSION;
+import static h07.H07Test.getCtElements;
+import static h07.MethodReference.CONVERT_PEANO_TO_NUMBER_EXPRESSION_CONVERT;
+import static h07.MethodReference.NUMBER_EXPRESSION_EVALUATE;
+import static h07.MethodReference.PEANO_NUMBER_EXPRESSION_EVALUATE;
+import static org.mockito.Mockito.CALLS_REAL_METHODS;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+import static org.tudalgo.algoutils.tutor.general.assertions.Assertions2.assertEquals;
+import static org.tudalgo.algoutils.tutor.general.assertions.Assertions2.contextBuilder;
+
+@TestForSubmission
+public class ConvertPeanoToNumberExpressionImplTest {
+
+    @Test
+    public void testDefinition() {
+        ClassReference.CONVERT_PEANO_TO_NUMBER_EXPRESSION_IMPL.assertCorrectlyDefined();
+    }
+
+    @Test
+    public void testNaming() {
+        ClassReference.CONVERT_PEANO_TO_NUMBER_EXPRESSION_IMPL.assertNamedCorrectly();
+    }
+
+    @Test
+    public void testPackage() {
+        ClassReference.CONVERT_PEANO_TO_NUMBER_EXPRESSION_IMPL.assertDefinedInCorrectPackage();
+    }
+
+    @ParameterizedTest
+    @JsonParameterSetTest(value = "ConvertPeanoToNumberExpressionImpl_X.json")
+    public void testEvaluate_X(JsonParameterSet params) throws Throwable {
+        performTest(params);
+    }
+
+    @ParameterizedTest
+    @JsonParameterSetTest(value = "ConvertPeanoToNumberExpressionImpl_0.json")
+    public void testEvaluate_0(JsonParameterSet params) throws Throwable {
+        performTest(params);
+    }
+
+    private static void performTest(JsonParameterSet params) throws Throwable {
+        int x = params.getInt("x");
+
+        Object numberExpression = mock(PEANO_NUMBER_EXPRESSION.getLink().reflection());
+        when(PEANO_NUMBER_EXPRESSION_EVALUATE.invoke(
+            numberExpression.getClass(),
+            numberExpression
+        )).thenReturn(NumberConverter.toPeanoNumber(x));
+
+        Object mock = mock(CONVERT_PEANO_TO_NUMBER_EXPRESSION_IMPL.getLink().reflection(), CALLS_REAL_METHODS);
+        Object returned = CONVERT_PEANO_TO_NUMBER_EXPRESSION_CONVERT.invoke(mock.getClass(), mock, numberExpression);
+
+        int actual = NUMBER_EXPRESSION_EVALUATE.invoke(returned.getClass(), returned);
+
+        assertEquals(x, actual, params.toContext("expected"), r -> "Value returned by convert() does not match expected.");
+    }
+
+    @Test
+    public void testConvertRequirements() {
+        CtMethod<?> evaluate =
+            ((BasicMethodLink) CONVERT_PEANO_TO_NUMBER_EXPRESSION_CONVERT.getLink(
+                CONVERT_PEANO_TO_NUMBER_EXPRESSION_IMPL.getLink().reflection(),
+                PEANO_NUMBER_EXPRESSION.getLink().reflection()
+            )).getCtElement();
+
+        getCtElements(List.of(CONVERT_PEANO_TO_NUMBER_EXPRESSION_IMPL.getLink().reflection()), CtLambda.class, evaluate)
+            .forEach(ctLambda -> {
+                    String body = ctLambda.toStringDebug();
+                    Context context = contextBuilder().add("Lambda", body).build();
+
+                    Assertions2.assertNull(
+                        ctLambda.getBody(),
+                        context,
+                        r -> "convert() does not use correct lambdas."
+                    );
+                }
+            );
+    }
+}

solution/H07/src/graderPrivate/java/h07/ConvertPeanoToNumberExpressionTest.java

@@ -0,0 +1,25 @@
+package h07;
+
+import org.junit.jupiter.api.Test;
+import org.sourcegrade.jagr.api.rubric.TestForSubmission;
+
+@TestForSubmission
+public class ConvertPeanoToNumberExpressionTest {
+
+    @Test
+    public void testDefinition() {
+        ClassReference.CONVERT_PEANO_TO_NUMBER_EXPRESSION.assertCorrectlyDefined();
+        MethodReference.CONVERT_PEANO_TO_NUMBER_EXPRESSION_CONVERT.assertCorrectlyDefined();
+    }
+
+    @Test
+    public void testNaming() {
+        ClassReference.CONVERT_PEANO_TO_NUMBER_EXPRESSION.assertNamedCorrectly();
+        MethodReference.CONVERT_PEANO_TO_NUMBER_EXPRESSION_CONVERT.assertNamedCorrectly();
+    }
+
+    @Test
+    public void testPackage() {
+        ClassReference.CONVERT_PEANO_TO_NUMBER_EXPRESSION.assertDefinedInCorrectPackage();
+    }
+}

solution/H07/src/graderPrivate/java/h07/H07Test.java

@@ -0,0 +1,59 @@
+package h07;
+
+import org.mockito.MockMakers;
+import org.mockito.MockSettings;
+import org.sourcegrade.jagr.api.testing.TestCycle;
+import org.sourcegrade.jagr.api.testing.extension.TestCycleResolver;
+import org.tudalgo.algoutils.tutor.general.reflections.BasicMethodLink;
+import spoon.reflect.code.CtBodyHolder;
+import spoon.reflect.code.CtInvocation;
+import spoon.reflect.declaration.CtElement;
+import spoon.reflect.declaration.CtMethod;
+import spoon.reflect.visitor.filter.TypeFilter;
+
+import java.util.List;
+import java.util.stream.Stream;
+
+import static org.mockito.Mockito.withSettings;
+
+public class H07Test {
+
+    public MockSettings getSettings() {
+
+        TestCycle cycle = TestCycleResolver.getTestCycle();
+
+        if (cycle != null) {
+            Thread.currentThread()
+                .setContextClassLoader((ClassLoader) TestCycleResolver.getTestCycle().getClassLoader());
+            return withSettings().mockMaker(MockMakers.PROXY);
+        }
+
+        return withSettings();
+    }
+
+    public static <T extends CtElement> Stream<T> getCtElements(final List<Class<?>> classesToSearch, final Class<T> toSearch,
+                                                                final CtBodyHolder bodyHolder) {
+        return bodyHolder.getElements(new TypeFilter<>(CtElement.class) {
+                @Override
+                public boolean matches(final CtElement element) {
+                    return (toSearch.isInstance(element) || (element instanceof CtInvocation<?>))
+                        && classesToSearch.contains(element.getParent(CtMethod.class).getDeclaringType().getActualClass());
+                }
+            })
+            .stream()
+            .filter(ctElement -> !ctElement.equals(bodyHolder))
+            .flatMap(element -> {
+                if (element instanceof final CtInvocation<?> call) {
+                    final var calledMethod = call.getExecutable();
+                    if (calledMethod.getDeclaringType() == null
+                        || !calledMethod.getDeclaringType().getQualifiedName().startsWith("h00.")) {
+                        return Stream.of();
+                    }
+                    final var actualCalledMethod = calledMethod.getActualMethod();
+                    final CtMethod<?> calledMethodCt = BasicMethodLink.of(actualCalledMethod).getCtElement();
+                    return getCtElements(classesToSearch, toSearch, calledMethodCt);
+                }
+                return Stream.of((T) element);
+            });
+    }
+}

solution/H07/src/graderPrivate/java/h07/H07_RubricProvider.java

@@ -0,0 +1,333 @@
+package h07;
+
+import static org.tudalgo.algoutils.tutor.general.jagr.RubricUtils.criterion;
+
+import org.sourcegrade.jagr.api.rubric.Criterion;
+import org.sourcegrade.jagr.api.rubric.JUnitTestRef;
+import org.sourcegrade.jagr.api.rubric.Rubric;
+import org.sourcegrade.jagr.api.rubric.RubricProvider;
+import org.tudalgo.algoutils.tutor.general.json.JsonParameterSet;
+
+public class H07_RubricProvider implements RubricProvider {
+
+    private static final Criterion H7_1_1 = Criterion.builder()
+            .shortDescription("H7.1.1 | NumberExpression")
+            .maxPoints(2)
+            .minPoints(0)
+            .addChildCriteria(
+                    criterion(
+                            "Das Interface NumberExpression wurde korrekt erstellt.",
+                            JUnitTestRef.ofMethod(() -> NumberExpressionTest.class.getMethod("testDefinition"))),
+                    criterion(
+                            "Das Interface PeanoNumberExpression wurde korrekt erstellt.",
+                            JUnitTestRef.ofMethod(() -> PeanoNumberExpressionTest.class.getMethod("testDefinition"))))
+            .build();
+
+    private static final Criterion H7_1_2 = Criterion.builder()
+            .shortDescription("H7.1.2 | ArithmeticExpression")
+            .maxPoints(2)
+            .minPoints(0)
+            .addChildCriteria(
+                    criterion(
+                            "Das Interface ArithmeticExpression wurde korrekt erstellt.",
+                            JUnitTestRef.ofMethod(() -> ArithmeticExpressionTest.class.getMethod("testDefinition"))),
+                    criterion(
+                            "Das Interface PeanoArithmeticExpression wurde korrekt erstellt.",
+                            JUnitTestRef
+                                    .ofMethod(() -> PeanoArithmeticExpressionTest.class.getMethod("testDefinition"))))
+            .build();
+
+    private static final Criterion H7_1 = Criterion.builder()
+            .shortDescription("H7.1 | Interfaces definieren")
+            .minPoints(0)
+            .addChildCriteria(
+                    H7_1_1,
+                    H7_1_2,
+                    criterion(
+                            "Alle Klassen und Methoden wurden korrekt benannt.",
+                            -1,
+                            JUnitTestRef.and(
+                                    JUnitTestRef.ofMethod(() -> NumberExpressionTest.class.getMethod("testNaming")),
+                                    JUnitTestRef
+                                            .ofMethod(() -> PeanoNumberExpressionTest.class.getMethod("testNaming")),
+                                    JUnitTestRef.ofMethod(() -> ArithmeticExpressionTest.class.getMethod("testNaming")),
+                                    JUnitTestRef.ofMethod(
+                                            () -> PeanoArithmeticExpressionTest.class.getMethod("testNaming")))),
+                    criterion(
+                            "Alle Klassen wurden im korrekten package definiert.",
+                            -1,
+                            JUnitTestRef.and(
+                                    JUnitTestRef.ofMethod(() -> NumberExpressionTest.class.getMethod("testPackage")),
+                                    JUnitTestRef
+                                            .ofMethod(() -> PeanoNumberExpressionTest.class.getMethod("testPackage")),
+                                    JUnitTestRef
+                                            .ofMethod(() -> ArithmeticExpressionTest.class.getMethod("testPackage")),
+                                    JUnitTestRef.ofMethod(
+                                            () -> PeanoArithmeticExpressionTest.class.getMethod("testPackage")))))
+            .build();
+
+    private static final Criterion H7_2_1 = Criterion.builder()
+            .shortDescription("H7.2.1 | Multiplikationstabelle")
+            .maxPoints(3)
+            .minPoints(0)
+            .addChildCriteria(
+                    criterion(
+                            "Für ArithmeticExpression wurden nur Lambda-Ausdrücke in Standardform und für NumberExpression nur "
+                                    + "Lambda-Ausdrücke in Kurzform verwendet.",
+                            JUnitTestRef.ofMethod(() -> NumberExpressionFactoryTest.class
+                                    .getMethod("testMultiplicationTableRequirements"))),
+                    criterion(
+                            "Die Multiplikationstabelle gibt für lowerBound = upperBound die korrekten Werte aus.",
+                            JUnitTestRef.ofMethod(() -> NumberExpressionFactoryTest.class.getMethod(
+                                    "multiplicationTableSimple",
+                                    JsonParameterSet.class))),
+                    criterion(
+                            "Die Multiplikationstabelle gibt für komplexere lowerBound und upperBound Werte die korrekten Werte aus.",
+                            JUnitTestRef.ofMethod(() -> NumberExpressionFactoryTest.class.getMethod(
+                                    "multiplicationTableComplex",
+                                    JsonParameterSet.class))))
+            .build();
+
+    private static final Criterion H7_2 = Criterion.builder()
+            .shortDescription("H7.2 | Multiplikationstabelle")
+            .minPoints(0)
+            .addChildCriteria(
+                    H7_2_1)
+            .build();
+
+    private static final Criterion H7_3_1 = Criterion.builder()
+            .shortDescription("H7.3.1 | PeanoAddExpression")
+            .minPoints(0)
+            .maxPoints(5)
+            .addChildCriteria(
+                    criterion(
+                            "Die Klasse PeanoAddExpression wurde korrekt erstellt.",
+                            JUnitTestRef.ofMethod(() -> PeanoAddExpressionTest.class.getMethod("testDefinition"))),
+                    criterion(
+                            "Die Methode evaluate gibt für X + 0 das korrekte Ergebnis zurück.",
+                            JUnitTestRef.ofMethod(() -> PeanoAddExpressionTest.class.getMethod("testEvaluate_X0",
+                                    JsonParameterSet.class))),
+                    criterion(
+                            "Die Methode evaluate gibt für 0 + X das korrekte Ergebnis zurück.",
+                            JUnitTestRef.ofMethod(() -> PeanoAddExpressionTest.class.getMethod("testEvaluate_0X",
+                                    JsonParameterSet.class))),
+                    criterion(
+                            "Die Methode evaluate gibt für X + Y das korrekte Ergebnis zurück.",
+                            2,
+                            JUnitTestRef.ofMethod(() -> PeanoAddExpressionTest.class.getMethod("testEvaluate_XY",
+                                    JsonParameterSet.class))),
+                    criterion(
+                            "Verbindliche Anforderung nicht erfüllt",
+                            -2,
+                            JUnitTestRef.ofMethod(
+                                    () -> PeanoAddExpressionTest.class.getMethod("testEvaluateRequirements"))))
+            .build();
+
+    private static final Criterion H7_3_2 = Criterion.builder()
+            .shortDescription("H7.3.2 | PeanoMultiplyExpression")
+            .minPoints(0)
+            .maxPoints(5)
+            .addChildCriteria(
+                    criterion(
+                            "Die Klasse PeanoMultiplyExpression wurde korrekt erstellt.",
+                            JUnitTestRef.ofMethod(() -> PeanoMultiplyExpressionTest.class.getMethod("testDefinition"))),
+                    criterion(
+                            "Die Methode evaluate gibt für X * 0 das korrekte Ergebnis zurück.",
+                            JUnitTestRef.ofMethod(() -> PeanoMultiplyExpressionTest.class.getMethod(
+                                    "testEvaluate_X0",
+                                    JsonParameterSet.class))),
+                    criterion(
+                            "Die Methode evaluate gibt für 0 * X das korrekte Ergebnis zurück.",
+                            JUnitTestRef.ofMethod(() -> PeanoMultiplyExpressionTest.class.getMethod(
+                                    "testEvaluate_0X",
+                                    JsonParameterSet.class))),
+                    criterion(
+                            "Die Methode evaluate gibt für X * Y das korrekte Ergebnis zurück.",
+                            2,
+                            JUnitTestRef.ofMethod(() -> PeanoMultiplyExpressionTest.class.getMethod(
+                                    "testEvaluate_XY",
+                                    JsonParameterSet.class))),
+                    criterion(
+                            "Verbindliche Anforderung nicht erfüllt",
+                            -2,
+                            JUnitTestRef.ofMethod(
+                                    () -> PeanoMultiplyExpressionTest.class.getMethod("testEvaluateRequirements"))))
+            .build();
+
+    private static final Criterion H7_3 = Criterion.builder()
+            .shortDescription("H7.3 | Peano Arithmetik")
+            .minPoints(0)
+            .addChildCriteria(
+                    H7_3_1,
+                    H7_3_2,
+                    criterion(
+                            "Alle Klassen und Methoden wurden korrekt benannt.",
+                            -1,
+                            JUnitTestRef.and(
+                                    JUnitTestRef.ofMethod(() -> PeanoAddExpressionTest.class.getMethod("testNaming")),
+                                    JUnitTestRef.ofMethod(
+                                            () -> PeanoMultiplyExpressionTest.class.getMethod("testNaming")))),
+                    criterion(
+                            "Alle Klassen wurden im korrekten package definiert.",
+                            -1,
+                            JUnitTestRef.and(
+                                    JUnitTestRef.ofMethod(() -> PeanoAddExpressionTest.class.getMethod("testPackage")),
+                                    JUnitTestRef.ofMethod(
+                                            () -> PeanoMultiplyExpressionTest.class.getMethod("testPackage")))))
+            .build();
+
+    private static final Criterion H7_4_1 = Criterion.builder()
+            .shortDescription("H7.4.1 | Interfaces für Map erstellen")
+            .maxPoints(2)
+            .minPoints(0)
+            .addChildCriteria(
+                    criterion(
+                            "Das Interface ConvertNumberToPeanoExpression wurde korrekt erstellt.",
+                            JUnitTestRef.ofMethod(
+                                    () -> ConvertNumberToPeanoExpressionTest.class.getMethod("testDefinition"))),
+                    criterion(
+                            "Das Interface ConvertPeanoToNumberExpression wurde korrekt erstellt.",
+                            JUnitTestRef.ofMethod(
+                                    () -> ConvertPeanoToNumberExpressionTest.class.getMethod("testDefinition"))))
+            .build();
+
+    private static final Criterion H7_4_2 = Criterion.builder()
+            .shortDescription("H7.4.2 | Conversions Implementieren")
+            .maxPoints(7)
+            .minPoints(0)
+            .addChildCriteria(
+                    criterion(
+                            "Die Klasse ConvertNumberToPeanoExpressionImpl wurde korrekt erstellt.",
+                            JUnitTestRef.ofMethod(
+                                    () -> ConvertNumberToPeanoExpressionImplTest.class.getMethod("testDefinition"))),
+                    criterion(
+                            "Die Methode convert von ConvertNumberToPeanoExpressionImpl gibt für 0 das korrekte Ergebnis zurück.",
+                            JUnitTestRef.ofMethod(() -> ConvertNumberToPeanoExpressionImplTest.class.getMethod(
+                                    "testEvaluate_0",
+                                    JsonParameterSet.class))),
+                    criterion(
+                            "Die Methode convert von ConvertNumberToPeanoExpressionImpl gibt für X das korrekte Ergebnis zurück.",
+                            JUnitTestRef.ofMethod(() -> ConvertNumberToPeanoExpressionImplTest.class.getMethod(
+                                    "testEvaluate_X",
+                                    JsonParameterSet.class))),
+                    criterion(
+                            "Die Klasse ConvertPeanoToNumberExpressionImpl wurde korrekt erstellt.",
+                            JUnitTestRef.ofMethod(
+                                    () -> ConvertPeanoToNumberExpressionImplTest.class.getMethod("testDefinition"))),
+                    criterion(
+                            "Die Methode convert von ConvertPeanoToNumberExpressionImpl gibt für 0 das korrekte Ergebnis zurück.",
+                            JUnitTestRef.ofMethod(() -> ConvertPeanoToNumberExpressionImplTest.class.getMethod(
+                                    "testEvaluate_0",
+                                    JsonParameterSet.class))),
+                    criterion(
+                            "Die Methode convert von ConvertPeanoToNumberExpressionImpl gibt für X das korrekte Ergebnis zurück.",
+                            2,
+                            JUnitTestRef.ofMethod(() -> ConvertPeanoToNumberExpressionImplTest.class.getMethod(
+                                    "testEvaluate_X",
+                                    JsonParameterSet.class))))
+            .build();
+
+    private static final Criterion H7_4_3 = Criterion.builder()
+            .shortDescription("H7.4.3 | Von Zahlen zu Peano-Zahlen")
+            .maxPoints(1)
+            .minPoints(0)
+            .addChildCriteria(
+                    criterion(
+                            "Die Methode fromNumberExpressions in PeanoNumberExpressionFactory wandelt einen Array von NumberExpressions "
+                                    + "korrekt um.",
+                            JUnitTestRef.ofMethod(() -> PeanoNumberExpressionFactoryTest.class
+                                    .getMethod("testFromNumberExpressions", JsonParameterSet.class))))
+            .build();
+
+    private static final Criterion H7_4_4 = Criterion.builder()
+            .shortDescription("H7.4.4 | Filter")
+            .maxPoints(3)
+            .minPoints(0)
+            .addChildCriteria(
+                    criterion(
+                            "Filter gibt für ein leeres Array ein leeres Array zurück.",
+                            JUnitTestRef.ofMethod(() -> NumberExpressionFactoryTest.class.getMethod("filter_empty",
+                                    JsonParameterSet.class))),
+                    criterion(
+                            "Filter gibt für ein Predicate, das immer true ist, das gesamte Array zurück und für ein Predicate, das immer "
+                                    + "false ist, ein leeres Array.",
+                            JUnitTestRef.and(
+                                    JUnitTestRef.ofMethod(() -> NumberExpressionFactoryTest.class.getMethod(
+                                            "filter_true",
+                                            JsonParameterSet.class)),
+                                    JUnitTestRef.ofMethod(() -> NumberExpressionFactoryTest.class.getMethod(
+                                            "filter_false",
+                                            JsonParameterSet.class)))),
+                    criterion(
+                            "Filter gibt für ein Predicate, welches nur durch vier teilbare Zahlen akzeptiert, nur die durch drei teilbaren"
+                                    + " Zahlen zurück.",
+                            JUnitTestRef.ofMethod(() -> NumberExpressionFactoryTest.class.getMethod("filter_complex",
+                                    JsonParameterSet.class))))
+            .build();
+
+    private static final Criterion H7_4_5 = Criterion.builder()
+            .shortDescription("H7.4.5 | Fold")
+            .maxPoints(2)
+            .minPoints(0)
+            .addChildCriteria(
+                    criterion(
+                            "Fold gibt für ein leeres Array das Initial zurück.",
+                            JUnitTestRef.ofMethod(() -> PeanoNumberExpressionFactoryTest.class.getMethod(
+                                    "fold_empty",
+                                    JsonParameterSet.class))),
+                    criterion(
+                            "Fold gibt für ein Array mit mehreren Elementen das korrekte Ergebnis zurück.",
+                            JUnitTestRef.ofMethod(() -> PeanoNumberExpressionFactoryTest.class.getMethod(
+                                    "fold_filled",
+                                    JsonParameterSet.class))))
+            .build();
+
+    private static final Criterion H7_4 = Criterion.builder()
+            .shortDescription("H7.4 | Funktionen höherer Ordnung")
+            .minPoints(0)
+            .addChildCriteria(
+                    H7_4_1,
+                    H7_4_2,
+                    H7_4_3,
+                    H7_4_4,
+                    H7_4_5,
+                    criterion(
+                            "Alle Klassen und Methoden wurden korrekt benannt.",
+                            -1,
+                            JUnitTestRef.and(
+                                    JUnitTestRef.ofMethod(
+                                            () -> ConvertNumberToPeanoExpressionTest.class.getMethod("testNaming")),
+                                    JUnitTestRef.ofMethod(
+                                            () -> ConvertPeanoToNumberExpressionTest.class.getMethod("testNaming")),
+                                    JUnitTestRef.ofMethod(
+                                            () -> ConvertNumberToPeanoExpressionImplTest.class.getMethod("testNaming")),
+                                    JUnitTestRef.ofMethod(() -> ConvertPeanoToNumberExpressionImplTest.class
+                                            .getMethod("testNaming")))),
+                    criterion(
+                            "Alle Klassen wurden im korrekten package definiert.",
+                            -1,
+                            JUnitTestRef.and(
+                                    JUnitTestRef.ofMethod(
+                                            () -> ConvertNumberToPeanoExpressionTest.class.getMethod("testPackage")),
+                                    JUnitTestRef.ofMethod(
+                                            () -> ConvertPeanoToNumberExpressionTest.class.getMethod("testPackage")),
+                                    JUnitTestRef.ofMethod(() -> ConvertNumberToPeanoExpressionImplTest.class
+                                            .getMethod("testPackage")),
+                                    JUnitTestRef.ofMethod(() -> ConvertPeanoToNumberExpressionImplTest.class
+                                            .getMethod("testPackage")))))
+            .build();
+
+    public static final Rubric RUBRIC = Rubric.builder()
+            .title("H07 | Peano Arithmetik")
+            .addChildCriteria(
+                    H7_1,
+                    H7_2,
+                    H7_3,
+                    H7_4)
+            .build();
+
+    @Override
+    public Rubric getRubric() {
+        return RUBRIC;
+    }
+}

solution/H07/src/graderPrivate/java/h07/MethodReference.java

@@ -0,0 +1,446 @@
+package h07;
+
+import org.tudalgo.algoutils.tutor.general.assertions.Context;
+import org.tudalgo.algoutils.tutor.general.match.Matcher;
+import org.tudalgo.algoutils.tutor.general.reflections.BasicConstructorLink;
+import org.tudalgo.algoutils.tutor.general.reflections.BasicTypeLink;
+import org.tudalgo.algoutils.tutor.general.reflections.ConstructorLink;
+import org.tudalgo.algoutils.tutor.general.reflections.Link;
+import org.tudalgo.algoutils.tutor.general.reflections.MethodLink;
+import org.tudalgo.algoutils.tutor.general.reflections.Modifier;
+import org.tudalgo.algoutils.tutor.general.reflections.TypeLink;
+import org.tudalgo.algoutils.tutor.general.reflections.WithModifiers;
+
+import java.lang.reflect.Executable;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.stream.Collectors;
+
+import static h07.ClassReference.ARITHMETIC_EXPRESSION;
+import static h07.ClassReference.CONVERT_NUMBER_TO_PEANO_EXPRESSION;
+import static h07.ClassReference.CONVERT_PEANO_TO_NUMBER_EXPRESSION;
+import static h07.ClassReference.NUMBER_EXPRESSION;
+import static h07.ClassReference.PEANO_ARITHMETIC_EXPRESSION;
+import static h07.ClassReference.PEANO_NUMBER_EXPRESSION;
+import static org.mockito.Mockito.mock;
+import static org.tudalgo.algoutils.tutor.general.assertions.Assertions2.assertEquals;
+import static org.tudalgo.algoutils.tutor.general.assertions.Assertions2.assertNotNull;
+import static org.tudalgo.algoutils.tutor.general.assertions.Assertions2.assertTrue;
+import static org.tudalgo.algoutils.tutor.general.assertions.Assertions2.contextBuilder;
+import static org.tudalgo.algoutils.tutor.general.assertions.Assertions2.fail;
+import static org.tudalgo.algoutils.tutor.general.reflections.Modifier.PUBLIC;
+
+public class MethodReference {
+
+    public static final MethodReference NUMBER_EXPRESSION_EVALUATE =
+        new MethodReference(NUMBER_EXPRESSION, "evaluate", new Modifier[] {PUBLIC}, int.class, new Class[] {});
+    public static final MethodReference PEANO_NUMBER_EXPRESSION_EVALUATE =
+        new MethodReference(PEANO_NUMBER_EXPRESSION, "evaluate", new Modifier[] {PUBLIC}, ClassReference.NATURAL_NUMBER.getLink().reflection(), new Class[] {});
+    public static final MethodReference ARITHMETIC_EXPRESSION_EVALUATE = new MethodReference(ARITHMETIC_EXPRESSION,
+        "evaluate",
+        new Modifier[] {PUBLIC},
+        NUMBER_EXPRESSION.getLink().reflection(),
+        NUMBER_EXPRESSION,
+        NUMBER_EXPRESSION
+    );
+    public static final MethodReference PEANO_ARITHMETIC_EXPRESSION_EVALUATE = new MethodReference(PEANO_ARITHMETIC_EXPRESSION,
+        "evaluate",
+        new Modifier[] {PUBLIC},
+        PEANO_NUMBER_EXPRESSION.getLink().reflection(),
+        PEANO_NUMBER_EXPRESSION,
+        PEANO_NUMBER_EXPRESSION
+    );
+    public static final MethodReference CONVERT_NUMBER_TO_PEANO_EXPRESSION_CONVERT = new MethodReference(
+        CONVERT_NUMBER_TO_PEANO_EXPRESSION,
+        "convert",
+        new Modifier[] {PUBLIC},
+        PEANO_NUMBER_EXPRESSION.getLink().reflection(),
+        NUMBER_EXPRESSION
+    );
+    public static final MethodReference CONVERT_PEANO_TO_NUMBER_EXPRESSION_CONVERT = new MethodReference(
+        CONVERT_PEANO_TO_NUMBER_EXPRESSION,
+        "convert",
+        new Modifier[] {PUBLIC},
+        NUMBER_EXPRESSION.getLink().reflection(),
+        PEANO_NUMBER_EXPRESSION
+    );
+
+    private final boolean isConstructor;
+    private final String name;
+    private final List<String> parameterClassNames;
+    private final Modifier[] expectedModifiers;
+    private final Link.Kind kind;
+    private final ClassReference clazz;
+    private Class<?>[] parameters;
+    private MethodLink methodLink;
+    private ConstructorLink constructorLink;
+
+    public MethodReference(ClassReference clazz, Modifier[] expectedModifiers, Class<?>... parameters) {
+        this.name = Link.Kind.CONSTRUCTOR.name();
+        this.parameters = parameters;
+        this.parameterClassNames = Arrays.stream(parameters).map(Class::getName).toList();
+        this.isConstructor = true;
+        this.expectedModifiers = expectedModifiers;
+        this.kind = Link.Kind.CONSTRUCTOR;
+        this.clazz = clazz;
+        if (!clazz.isDefined()) {
+            return;
+        }
+        try {
+            constructorLink = BasicConstructorLink.of(clazz.getLink().reflection().getDeclaredConstructor(parameters));
+        } catch (NoSuchMethodException ignored) {
+        }
+    }
+
+    public MethodReference(ClassReference clazz, Modifier[] expectedModifiers, ClassReference... parameters) {
+        this.name = Link.Kind.CONSTRUCTOR.name();
+        this.parameterClassNames = Arrays.stream(parameters).map(ClassReference::getName).toList();
+        this.isConstructor = true;
+        this.expectedModifiers = expectedModifiers;
+        this.kind = Link.Kind.CONSTRUCTOR;
+        this.clazz = clazz;
+        if (!clazz.isDefined()) {
+            return;
+        }
+        for (ClassReference ref : parameters) {
+            if (!ref.isDefined()) {
+                return;
+            }
+        }
+        this.parameters = Arrays.stream(parameters).map(p -> p.getLink().reflection()).toArray(Class[]::new);
+        try {
+            constructorLink = BasicConstructorLink.of(
+                clazz.getLink().reflection().getDeclaredConstructor(
+                    Arrays.stream(parameters).map(p -> p.getLink().reflection()).toArray(Class[]::new)
+                )
+            );
+        } catch (NoSuchMethodException ignored) {
+        }
+    }
+
+    public MethodReference(ClassReference clazz, String name, Modifier[] expectedModifiers, Class<?> returnValue,
+                           Class<?>... parameters) {
+        this.name = name;
+        this.parameters = parameters;
+        this.parameterClassNames = Arrays.stream(parameters).map(Class::getName).toList();
+        this.isConstructor = false;
+        this.expectedModifiers = expectedModifiers;
+        this.kind = Link.Kind.METHOD;
+        this.clazz = clazz;
+        if (!clazz.isDefined()) {
+            return;
+        }
+        methodLink = clazz.getLink().getMethod(Tests.stringMatcher(name));
+    }
+
+    public MethodReference(ClassReference clazz, String name, Modifier[] expectedModifiers, Class<?> returnValue,
+                           ClassReference... parameters) {
+        this.name = name;
+        this.isConstructor = false;
+        this.expectedModifiers = expectedModifiers;
+        this.parameterClassNames = Arrays.stream(parameters).map(ClassReference::getName).toList();
+        this.kind = Link.Kind.METHOD;
+        this.clazz = clazz;
+        if (!clazz.isDefined()) {
+            return;
+        }
+        for (ClassReference ref : parameters) {
+            if (!ref.isDefined()) {
+                return;
+            }
+        }
+        this.parameters = Arrays.stream(parameters).map(p -> p.getLink().reflection()).toArray(Class[]::new);
+        methodLink = clazz.getLink().getMethod(Tests.stringMatcher(name));
+
+    }
+
+    public WithModifiers getLink() {
+        return methodLink != null ? methodLink : constructorLink;
+    }
+
+    public WithModifiers getLink(Class<?> calledClass, Class<?>... parameters) {
+        MethodLink actual = BasicTypeLink.of(calledClass).getMethod(Tests.stringMatcher(name));
+        if (actual != null) {
+            List<Class<?>> actualParameters = actual.typeList().stream().map(TypeLink::reflection).collect(Collectors.toList());
+
+            Map<Class<?>, Integer> occurrencesActual = actualParameters.stream().collect(Collectors.groupingBy(
+                obj -> obj,
+                Collectors.summingInt(obj -> 1)
+            ));
+            Map<Class<?>, Integer> occurrencesExpected = Arrays.stream(parameters).collect(Collectors.groupingBy(
+                obj -> obj == null ? MethodReference.class : obj,
+                Collectors.summingInt(obj -> 1)
+            ));
+
+            boolean hasCorrectParams = Arrays.stream(parameters).allMatch(
+                param -> actualParameters.stream().anyMatch(
+                    actualParam -> param == null || (actualParam.isAssignableFrom(param)
+                        && occurrencesActual.getOrDefault(actualParam, 0) >= occurrencesExpected.getOrDefault(param, 0))
+                )
+            );
+            if (parameters.length != actualParameters.size() || !hasCorrectParams) {
+                return null;
+            }
+            methodLink = actual;
+            return actual;
+        }
+        if (!clazz.isDefined()) {
+            return null;
+        }
+        if (isConstructor) {
+            ConstructorLink link = clazz.getLink().getConstructor(
+                Matcher.of(
+                    (c) -> {
+                        List<? extends Class<?>> types = c.typeList().stream().map(TypeLink::reflection).toList();
+                        if (parameters == null || types.size() != parameters.length) {
+                            return false;
+                        }
+                        for (int i = 0; i < types.size(); i++) {
+                            if (parameters[i] == null || !types.get(i).isAssignableFrom(parameters[i])) {
+                                return false;
+                            }
+                        }
+                        return true;
+                    }
+                )
+            );
+            constructorLink = link;
+            return link;
+        }
+        return null;
+    }
+
+    public WithModifiers assertDefined(Class<?> calledClass, Class<?>... parameters) {
+        Context context = contextBuilder()
+            .add("expected class", clazz.getName())
+            .add("expected kind", kind)
+            .add("expected name", name)
+            .add("expected parameter", parameterClassNames)
+            .build();
+        MethodLink actual = BasicTypeLink.of(calledClass).getMethod(Tests.stringMatcher(name));
+        if (actual != null) {
+
+            List<Class<?>> actualParameters = actual.typeList().stream().map(TypeLink::reflection).collect(Collectors.toList());
+
+            Map<Class<?>, Integer> occurrencesActual = actualParameters.stream().collect(Collectors.groupingBy(
+                obj -> obj,
+                Collectors.summingInt(obj -> 1)
+            ));
+            Map<Class<?>, Integer> occurrencesExpected = Arrays.stream(parameters).collect(Collectors.groupingBy(
+                obj -> obj == null ? MethodReference.class : obj,
+                Collectors.summingInt(obj -> 1)
+            ));
+
+            boolean hasCorrectParams = Arrays.stream(parameters).allMatch(
+                param -> actualParameters.stream().anyMatch(
+                    actualParam -> param == null || (actualParam.isAssignableFrom(param)
+                        && occurrencesActual.getOrDefault(actualParam, 0) >= occurrencesExpected.getOrDefault(param, 0))
+                )
+            );
+
+            context = contextBuilder()
+                .add(context)
+                .add("actual Parameters", actualParameters)
+                .add("called with", Arrays.toString(parameters))
+                .build();
+
+            assertEquals(
+                parameters.length,
+                actualParameters.size(),
+                context,
+                r -> String.format("%s does not have the right number of parameters", name)
+            );
+
+            assertTrue(
+                hasCorrectParams,
+                context,
+                r -> String.format("%s does not have the right parameters", name)
+            );
+            methodLink = actual;
+            return actual;
+        }
+        if (!clazz.isDefined()) {
+            fail(
+                context,
+                r -> String.format(
+                    "Can not find %s. The Class of the method does not exist or could not be found.",
+                    name
+                )
+            );
+        }
+        if (isConstructor) {
+            ConstructorLink link = clazz.getLink().getConstructor(
+                Matcher.of(
+                    (c) -> {
+                        List<? extends Class<?>> types = c.typeList().stream().map(TypeLink::reflection).toList();
+                        if (parameters == null || types.size() != parameters.length) {
+                            return false;
+                        }
+                        for (int i = 0; i < types.size(); i++) {
+                            if (parameters[i] == null || !types.get(i).isAssignableFrom(parameters[i])) {
+                                return false;
+                            }
+                        }
+                        return true;
+                    }
+                )
+            );
+            if (link != null) {
+                return link;
+            }
+            return fail(
+                context,
+                r -> String.format(
+                    "Could not find %s in class %s. The constructor does not exist or has wrong Parameters.",
+                    name,
+                    clazz.getLink().name()
+                )
+            );
+        }
+        return fail(
+            context,
+            r -> String.format(
+                "Can not find %s in class %s. The Method does not exist or could not be found.",
+                name,
+                calledClass.getName()
+            )
+        );
+    }
+
+    public void assertCorrectlyDefined() {
+        assertDefined(clazz.getLink().reflection(), parameters);
+
+        WithModifiers link = assertDefined(clazz.getLink().reflection(), parameters);
+        String name =
+            link.kind() == Link.Kind.METHOD ? ((MethodLink) link).reflection().getName() : Link.Kind.CONSTRUCTOR.name();
+        Modifier[] actualModifiers =
+            Arrays.stream(Modifier.values()).filter(m -> m.is(link.modifiers())).toArray(Modifier[]::new);
+        Context context = contextBuilder()
+            .add("expected class", clazz.getLink().name())
+            .add("expected kind", kind)
+            .add("expected name", name)
+            .add(
+                "expected modifier",
+                Arrays.stream(expectedModifiers).map(Modifier::keyword).collect(Collectors.joining(", "))
+            )
+            .add("class", ((Executable) link.reflection()).getDeclaringClass().getName())
+            .add("kind", link.kind())
+            .add("name", name)
+            .add("modifier", Arrays.stream(actualModifiers).map(Modifier::keyword).collect(Collectors.joining(", ")))
+            .build();
+
+        assertNotNull(link, context, r -> "Could not find method %s.".formatted(name));
+        assertEquals(
+            clazz.getLink().reflection(),
+            ((Executable) link.reflection()).getDeclaringClass(),
+            context,
+            r -> "Declaring Class does not match expected Class."
+        );
+        assertEquals(link.kind(), link.kind(), context, r -> "Kind does not match expected kind.");
+
+        assertTrue(
+            Set.of(actualModifiers).containsAll(Set.of(expectedModifiers)),
+            context,
+            r -> "The modifiers of the Method do not match the expected modifiers."
+        );
+    }
+
+    public void assertNamedCorrectly() {
+        WithModifiers link = getLink(clazz.getLink().reflection(), parameters);
+        if (link == null) {
+            return;
+        }
+
+        String name =
+            link.kind() == Link.Kind.METHOD ? ((MethodLink) link).reflection().getName() : Link.Kind.CONSTRUCTOR.name();
+        Context context = contextBuilder()
+            .add("expected name", name)
+            .add("name", name)
+            .build();
+
+        assertEquals(this.name, name, context, r -> "The name of the Method does not match the expected name.");
+    }
+
+    public <T> T invoke(Class<?> calledClass, Object instance, Object... parameter) throws Throwable {
+        Link link = assertDefined(
+            calledClass,
+            Arrays.stream(parameter).map(o -> o != null ? o.getClass() : null).toArray(Class[]::new)
+        );
+        if (instance == null && !(link instanceof ConstructorLink)) {
+            throw new IllegalArgumentException(
+                "Could not invoke %s.%s() as object that the function should have been called on is null.".formatted(
+                    clazz.getName(),
+                    name
+                ));
+        }
+        if (link instanceof MethodLink l) {
+            return l.invoke(instance, parameter);
+        } else if (link instanceof ConstructorLink l) {
+            return l.invoke(parameter);
+        } else {
+            return null;
+        }
+    }
+
+    public <T> T invokeBestEffort(Class<?> calledClass, Object instance, Object... parameter) throws Throwable {
+        WithModifiers link = getLink();
+
+        if (link == null) {
+            Context context = contextBuilder()
+                .add("expected class", clazz.getName())
+                .add("expected kind", kind)
+                .add("expected name", name)
+                .add("expected parameter", parameterClassNames)
+                .build();
+            fail(
+                context,
+                r -> String.format(
+                    "Can not find %s in class %s. The Method does not exist or could not be found.",
+                    name,
+                    calledClass.getName()
+                )
+            );
+        }
+
+        Class<?>[] actualParameter = ((Executable) link.reflection()).getParameterTypes();
+
+        try {
+            return invoke(calledClass, instance, parameter);
+        } catch (Throwable ignored) {
+            ignored.printStackTrace();
+        }
+        if (actualParameter.length == 0) {
+            if (link instanceof MethodLink l) {
+                return l.invoke(instance);
+            } else if (link instanceof ConstructorLink l) {
+                return l.invoke();
+            } else {
+                return null;
+            }
+        }
+
+        Object[] mocks = Arrays.stream(actualParameter)
+            .map(p -> {
+                if (p.equals(String.class)) {
+                    return "";
+                }
+                return mock(p);
+            })
+            .toArray();
+        for (int i = 0; i < parameter.length && i < mocks.length; i++) {
+            if (mocks[i].getClass().isAssignableFrom(parameter[i].getClass())) {
+                mocks[i] = parameter[i];
+            }
+        }
+
+        if (link instanceof MethodLink l) {
+            return l.invoke(instance, mocks);
+        } else if (link instanceof ConstructorLink l) {
+            return l.invoke(mocks);
+        } else {
+            return null;
+        }
+    }
+}

solution/H07/src/graderPrivate/java/h07/NumberConverter.java

@@ -0,0 +1,44 @@
+package h07;
+
+import java.lang.reflect.InvocationTargetException;
+
+import static h07.ClassReference.NUMBER_EXPRESSION;
+import static h07.ClassReference.PEANO_NUMBER_EXPRESSION;
+import static h07.MethodReference.NUMBER_EXPRESSION_EVALUATE;
+import static h07.MethodReference.PEANO_NUMBER_EXPRESSION_EVALUATE;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+public class NumberConverter {
+
+    public static int toNaturalNumber(Object peanoNumber) {
+        String representation = peanoNumber.toString();
+        return representation.length() - representation.replace("S", "").length();
+    }
+
+    public static Object toPeanoNumber(int number) {
+        Object peanoNumber = null;
+        try {
+            peanoNumber = ClassReference.ZERO.getLink().reflection().getConstructor().newInstance();
+
+            for (int i = 0; i < number; i++) {
+                peanoNumber = ClassReference.SUCCESSOR.getLink().reflection().getConstructor(ClassReference.NATURAL_NUMBER.getLink().reflection()).newInstance(peanoNumber);
+            }
+            return peanoNumber;
+        } catch (InstantiationException | NoSuchMethodException | InvocationTargetException | IllegalAccessException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    public static Object toNumberExpression(int number) throws Throwable {
+        Object numberExpression = mock(NUMBER_EXPRESSION.getLink().reflection());
+        when(NUMBER_EXPRESSION_EVALUATE.invoke(numberExpression.getClass(), numberExpression)).thenReturn(number);
+        return numberExpression;
+    }
+
+    public static Object toPeanoNumberExpression(int number) throws Throwable {
+        Object numberExpression = mock(PEANO_NUMBER_EXPRESSION.getLink().reflection());
+        when(PEANO_NUMBER_EXPRESSION_EVALUATE.invoke(numberExpression.getClass(), numberExpression)).thenReturn(toPeanoNumber(number));
+        return numberExpression;
+    }
+}

solution/H07/src/graderPrivate/java/h07/NumberExpressionFactoryTest.java

@@ -0,0 +1,219 @@
+package h07;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.sourcegrade.jagr.api.rubric.TestForSubmission;
+import org.tudalgo.algoutils.tutor.general.assertions.Assertions2;
+import org.tudalgo.algoutils.tutor.general.assertions.Context;
+import org.tudalgo.algoutils.tutor.general.json.JsonParameterSet;
+import org.tudalgo.algoutils.tutor.general.json.JsonParameterSetTest;
+import org.tudalgo.algoutils.tutor.general.match.BasicStringMatchers;
+import org.tudalgo.algoutils.tutor.general.reflections.BasicMethodLink;
+import org.tudalgo.algoutils.tutor.general.reflections.BasicTypeLink;
+import org.tudalgo.algoutils.tutor.general.reflections.MethodLink;
+import spoon.reflect.code.CtLambda;
+import spoon.reflect.declaration.CtMethod;
+
+import java.lang.reflect.Array;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.function.IntPredicate;
+
+import static h07.ClassReference.NUMBER_EXPRESSION;
+import static h07.H07Test.getCtElements;
+import static h07.MethodReference.NUMBER_EXPRESSION_EVALUATE;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+import static org.tudalgo.algoutils.tutor.general.assertions.Assertions2.*;
+
+@TestForSubmission
+public class NumberExpressionFactoryTest {
+
+    @ParameterizedTest
+    @JsonParameterSetTest(value = "NumberExpressionFactory_multiply_Simple.json")
+    public void multiplicationTableSimple(JsonParameterSet params) throws Throwable {
+        performTest_multiplication(params);
+    }
+
+    @ParameterizedTest
+    @JsonParameterSetTest(value = "NumberExpressionFactory_multiply_Complex.json")
+    public void multiplicationTableComplex(JsonParameterSet params) throws Throwable {
+        performTest_multiplication(params);
+    }
+
+    private static void performTest_multiplication(JsonParameterSet params) throws Throwable {
+        int lowerBound = params.getInt("lowerBound");
+        int upperBound = params.getInt("upperBound");
+
+        List<Integer> expected = new ArrayList<>();
+        params.getRootNode().get("expected").forEach(value -> expected.add(value.intValue()));
+
+        Context context = params.toContext();
+
+        List<Object> actualExpressions = multiplicationTable(lowerBound, upperBound);
+        List<Integer> actual = actualExpressions.stream().map(expr -> {
+            try {
+                return NUMBER_EXPRESSION_EVALUATE.<Integer>invoke(expr.getClass(), expr);
+            } catch (Throwable e) {
+                throw new RuntimeException(e);
+            }
+        }).toList();
+
+        assertEquals(expected, actual, context, r -> "Returned multiplication table does not match expected.");
+    }
+
+    private static List<Object> multiplicationTable(int lowerBound, int upperBound) throws Throwable {
+        int numberOfNumbers = upperBound - lowerBound + 1;
+        List<Object> baseNumbers = new ArrayList<>(numberOfNumbers);
+
+        for (int i = lowerBound; i <= upperBound; i++) {
+
+            Object expression = NumberConverter.toNumberExpression(i);
+            baseNumbers.add(expression);
+        }
+
+        MethodLink multiplicationLink = BasicMethodLink.of(Arrays.stream(NumberExpressionFactory.class.getMethods())
+            .filter(method -> method.getParameterCount() == 1 && method.getName().equals("multiplicationTable"))
+            .findFirst()
+            .get());
+
+        if (multiplicationLink == null) {
+            throw new RuntimeException("Could not find method NumberExpressionFactory.multiplicationTable()");
+        }
+
+        Object returned = multiplicationLink.invokeStatic((Object) (baseNumbers.toArray((Object[]) Array.newInstance(
+            NUMBER_EXPRESSION.getLink().reflection(),
+            0
+        ))));
+
+        try {
+            return List.of((Object[]) returned);
+        } catch (NullPointerException e) {
+            fail(emptyContext(), r -> "multiplicationTable() returned null or an array containing null");
+        }
+        return null;
+    }
+
+    @ParameterizedTest
+    @JsonParameterSetTest(value = "NumberExpressionFactory_filter_empty.json")
+    public void filter_empty(JsonParameterSet params) throws Throwable {
+        performTest_filter(params);
+    }
+
+    @ParameterizedTest
+    @JsonParameterSetTest(value = "NumberExpressionFactory_filter_true.json")
+    public void filter_true(JsonParameterSet params) throws Throwable {
+        performTest_filter(params);
+    }
+
+    @ParameterizedTest
+    @JsonParameterSetTest(value = "NumberExpressionFactory_filter_false.json")
+    public void filter_false(JsonParameterSet params) throws Throwable {
+        performTest_filter(params);
+    }
+
+    @ParameterizedTest
+    @JsonParameterSetTest(value = "NumberExpressionFactory_filter_complex.json")
+    public void filter_complex(JsonParameterSet params) throws Throwable {
+        performTest_filter(params);
+    }
+
+    private static void performTest_filter(JsonParameterSet params) throws Throwable {
+        List<Integer> inputs = new ArrayList<>();
+        params.getRootNode().get("inputs").forEach(value -> inputs.add(value.intValue()));
+
+        Map<Integer, Boolean> filterMappings = new HashMap<>();
+        AtomicInteger currentElem = new AtomicInteger();
+        params.getRootNode()
+            .get("filter")
+            .forEach(value -> filterMappings.put(inputs.get(currentElem.getAndIncrement()), value.booleanValue()));
+
+        List<Integer> expected = new ArrayList<>();
+        params.getRootNode().get("expected").forEach(value -> expected.add(value.intValue()));
+
+        IntPredicate predicate = filterMappings::get;
+
+        List<Object> baseNumbers = new ArrayList<>();
+        inputs.forEach(input -> {
+            Object expression = mock(NUMBER_EXPRESSION.getLink().reflection());
+            try {
+                when(NUMBER_EXPRESSION_EVALUATE.invoke(NUMBER_EXPRESSION.getLink().reflection(), expression)).thenReturn(input);
+            } catch (Throwable e) {
+                throw new RuntimeException(e);
+            }
+            baseNumbers.add(expression);
+        });
+
+        MethodLink filterLink = BasicTypeLink.of(NumberExpressionFactory.class)
+                    .getMethod(BasicStringMatchers.identical("filter"));
+
+        if (filterLink == null) {
+            fail(emptyContext(), r -> "Could not find method NumberExpressionFactory.filter()");
+        }
+
+        List<Object> actualExpressions = List.of(
+            filterLink.invokeStatic(
+                baseNumbers.toArray((Object[]) Array.newInstance(NUMBER_EXPRESSION.getLink().reflection(), 0)),
+                predicate
+            )
+        );
+        List<Integer> actual = actualExpressions.stream().map(expr -> {
+            try {
+                return NUMBER_EXPRESSION_EVALUATE.<Integer>invoke(expr.getClass(), expr);
+            } catch (Throwable e) {
+                throw new RuntimeException(e);
+            }
+        }).toList();
+
+        Context context = contextBuilder()
+            .add("inputs", inputs)
+            .add("filter", filterMappings)
+            .add("expected", expected)
+            .build();
+
+        assertEquals(expected, actual, context, r -> "Returned List of expressions does not match expected list.");
+    }
+
+    @Test
+    public void testMultiplicationTableRequirements() throws Throwable {
+        CtMethod<?> multiplicationTable = BasicMethodLink.of(Arrays.stream(NumberExpressionFactory.class.getMethods())
+                .filter(method -> method.getParameterCount() == 1 && method.getName().equals("multiplicationTable"))
+                .findFirst()
+                .get())
+            .getCtElement();
+
+        List<CtLambda> lambdas =
+            getCtElements(List.of(NumberExpressionFactory.class), CtLambda.class, multiplicationTable).toList();
+        boolean hasCorrectLambdas = lambdas.stream()
+            .anyMatch(ctLambda -> {
+                    if (ctLambda.getBody() == null) {
+                        return false;
+                    }
+
+                    List<CtLambda> innerLambdas =
+                        getCtElements(List.of(NumberExpressionFactory.class), CtLambda.class, ctLambda).toList();
+
+                    return innerLambdas.size() == 1 && innerLambdas.get(0).getBody() == null;
+                }
+            );
+
+        Assertions2.assertTrue(
+            hasCorrectLambdas,
+            contextBuilder().add("Lambdas", lambdas.stream().map(CtLambda::toStringDebug).toList()).build(),
+            r -> "multiplicationTable() does not use correct lambdas."
+        );
+
+        boolean returnsArrayOfLambda =
+            multiplicationTable(0, 2).stream().allMatch(it -> it.getClass().getName().contains("$$Lambda"));
+
+        Assertions2.assertTrue(
+            returnsArrayOfLambda,
+            emptyContext(),
+            r -> "multiplicationTable() does not return array of objects created from lambdas."
+        );
+    }
+}

solution/H07/src/graderPrivate/java/h07/NumberExpressionTest.java

@@ -0,0 +1,25 @@
+package h07;
+
+import org.junit.jupiter.api.Test;
+import org.sourcegrade.jagr.api.rubric.TestForSubmission;
+
+@TestForSubmission
+public class NumberExpressionTest extends H07Test {
+
+    @Test
+    public void testDefinition() {
+        ClassReference.NUMBER_EXPRESSION.assertCorrectlyDefined();
+        MethodReference.NUMBER_EXPRESSION_EVALUATE.assertCorrectlyDefined();
+    }
+
+    @Test
+    public void testNaming() {
+        ClassReference.NUMBER_EXPRESSION.assertNamedCorrectly();
+        MethodReference.NUMBER_EXPRESSION_EVALUATE.assertNamedCorrectly();
+    }
+
+    @Test
+    public void testPackage() {
+        ClassReference.NUMBER_EXPRESSION.assertDefinedInCorrectPackage();
+    }
+}

solution/H07/src/graderPrivate/java/h07/PeanoAddExpressionTest.java

@@ -0,0 +1,107 @@
+package h07;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.sourcegrade.jagr.api.rubric.TestForSubmission;
+import org.tudalgo.algoutils.tutor.general.assertions.Assertions2;
+import org.tudalgo.algoutils.tutor.general.assertions.Context;
+import org.tudalgo.algoutils.tutor.general.json.JsonParameterSet;
+import org.tudalgo.algoutils.tutor.general.json.JsonParameterSetTest;
+import org.tudalgo.algoutils.tutor.general.reflections.BasicMethodLink;
+import spoon.reflect.code.CtLambda;
+import spoon.reflect.declaration.CtMethod;
+
+import java.util.List;
+
+import static h07.ClassReference.PEANO_ADD_EXPRESSION;
+import static h07.ClassReference.PEANO_NUMBER_EXPRESSION;
+import static h07.H07Test.getCtElements;
+import static h07.MethodReference.PEANO_ARITHMETIC_EXPRESSION_EVALUATE;
+import static h07.MethodReference.PEANO_NUMBER_EXPRESSION_EVALUATE;
+import static org.mockito.Mockito.CALLS_REAL_METHODS;
+import static org.mockito.Mockito.mock;
+import static org.tudalgo.algoutils.tutor.general.assertions.Assertions2.assertEquals;
+import static org.tudalgo.algoutils.tutor.general.assertions.Assertions2.contextBuilder;
+
+@TestForSubmission
+public class PeanoAddExpressionTest {
+
+    @Test
+    public void testDefinition() {
+        ClassReference.PEANO_ADD_EXPRESSION.assertCorrectlyDefined();
+    }
+
+    @Test
+    public void testNaming() {
+        ClassReference.PEANO_ADD_EXPRESSION.assertNamedCorrectly();
+    }
+
+    @Test
+    public void testPackage() {
+        ClassReference.PEANO_ADD_EXPRESSION.assertDefinedInCorrectPackage();
+    }
+
+    @ParameterizedTest
+    @JsonParameterSetTest(value = "PeanoAddExpression_0X.json")
+    public void testEvaluate_0X(JsonParameterSet params) throws Throwable {
+        performTest(params);
+    }
+
+    @ParameterizedTest
+    @JsonParameterSetTest(value = "PeanoAddExpression_X0.json")
+    public void testEvaluate_X0(JsonParameterSet params) throws Throwable {
+        performTest(params);
+    }
+
+    @ParameterizedTest
+    @JsonParameterSetTest(value = "PeanoAddExpression_XY.json")
+    public void testEvaluate_XY(JsonParameterSet params) throws Throwable {
+        performTest(params);
+    }
+
+    private static void performTest(JsonParameterSet params) throws Throwable {
+        int x = params.getInt("x");
+        int y = params.getInt("y");
+        int expected = params.getInt("expected");
+
+        Object xPeano = NumberConverter.toPeanoNumberExpression(x);
+        Object yPeano = NumberConverter.toPeanoNumberExpression(y);
+
+        Object mock = mock(PEANO_ADD_EXPRESSION.getLink().reflection(), CALLS_REAL_METHODS);
+        Object returned = PEANO_ARITHMETIC_EXPRESSION_EVALUATE.invoke(mock.getClass(), mock, xPeano, yPeano);
+
+        Object actualPeano = PEANO_NUMBER_EXPRESSION_EVALUATE.invoke(returned.getClass(), returned);
+
+        int actual = NumberConverter.toNaturalNumber(actualPeano);
+
+        assertEquals(
+            expected,
+            actual,
+            params.toContext("expected"),
+            r -> "Value returned by PeanoAddExpression does not match expected."
+        );
+    }
+
+    @Test
+    public void testEvaluateRequirements() {
+        CtMethod<?> evaluate =
+            ((BasicMethodLink) PEANO_ARITHMETIC_EXPRESSION_EVALUATE.getLink(
+                PEANO_ADD_EXPRESSION.getLink().reflection(),
+                PEANO_NUMBER_EXPRESSION.getLink().reflection(),
+                PEANO_NUMBER_EXPRESSION.getLink().reflection()
+            )).getCtElement();
+
+        getCtElements(List.of(PEANO_ADD_EXPRESSION.getLink().reflection()), CtLambda.class, evaluate)
+            .forEach(ctLambda -> {
+                    String body = ctLambda.toStringDebug();
+                    Context context = contextBuilder().add("Lambda", body).build();
+
+                    Assertions2.assertNotNull(
+                        ctLambda.getBody(),
+                        context,
+                        r -> "evaluate() does not use correct lambdas."
+                    );
+                }
+            );
+    }
+}

solution/H07/src/graderPrivate/java/h07/PeanoArithmeticExpressionTest.java

@@ -0,0 +1,25 @@
+package h07;
+
+import org.junit.jupiter.api.Test;
+import org.sourcegrade.jagr.api.rubric.TestForSubmission;
+
+@TestForSubmission
+public class PeanoArithmeticExpressionTest {
+
+    @Test
+    public void testDefinition() {
+        ClassReference.PEANO_ARITHMETIC_EXPRESSION.assertCorrectlyDefined();
+        MethodReference.PEANO_ARITHMETIC_EXPRESSION_EVALUATE.assertCorrectlyDefined();
+    }
+
+    @Test
+    public void testNaming() {
+        ClassReference.PEANO_ARITHMETIC_EXPRESSION.assertNamedCorrectly();
+        MethodReference.PEANO_ARITHMETIC_EXPRESSION_EVALUATE.assertNamedCorrectly();
+    }
+
+    @Test
+    public void testPackage() {
+        ClassReference.PEANO_ARITHMETIC_EXPRESSION.assertDefinedInCorrectPackage();
+    }
+}

solution/H07/src/graderPrivate/java/h07/PeanoMultiplyExpressionTest.java

@@ -0,0 +1,107 @@
+package h07;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.sourcegrade.jagr.api.rubric.TestForSubmission;
+import org.tudalgo.algoutils.tutor.general.assertions.Assertions2;
+import org.tudalgo.algoutils.tutor.general.assertions.Context;
+import org.tudalgo.algoutils.tutor.general.json.JsonParameterSet;
+import org.tudalgo.algoutils.tutor.general.json.JsonParameterSetTest;
+import org.tudalgo.algoutils.tutor.general.reflections.BasicMethodLink;
+import spoon.reflect.code.CtLambda;
+import spoon.reflect.declaration.CtMethod;
+
+import java.util.List;
+
+import static h07.ClassReference.PEANO_MULTIPLY_EXPRESSION;
+import static h07.ClassReference.PEANO_NUMBER_EXPRESSION;
+import static h07.H07Test.getCtElements;
+import static h07.MethodReference.PEANO_ARITHMETIC_EXPRESSION_EVALUATE;
+import static h07.MethodReference.PEANO_NUMBER_EXPRESSION_EVALUATE;
+import static org.mockito.Mockito.CALLS_REAL_METHODS;
+import static org.mockito.Mockito.mock;
+import static org.tudalgo.algoutils.tutor.general.assertions.Assertions2.assertEquals;
+import static org.tudalgo.algoutils.tutor.general.assertions.Assertions2.contextBuilder;
+
+@TestForSubmission
+public class PeanoMultiplyExpressionTest {
+
+    @Test
+    public void testDefinition() {
+        ClassReference.PEANO_MULTIPLY_EXPRESSION.assertCorrectlyDefined();
+    }
+
+    @Test
+    public void testNaming() {
+        ClassReference.PEANO_MULTIPLY_EXPRESSION.assertNamedCorrectly();
+    }
+
+    @Test
+    public void testPackage() {
+        ClassReference.PEANO_MULTIPLY_EXPRESSION.assertDefinedInCorrectPackage();
+    }
+
+    @ParameterizedTest
+    @JsonParameterSetTest(value = "PeanoMultiplyExpression_0X.json")
+    public void testEvaluate_0X(JsonParameterSet params) throws Throwable {
+        performTest(params);
+    }
+
+    @ParameterizedTest
+    @JsonParameterSetTest(value = "PeanoMultiplyExpression_X0.json")
+    public void testEvaluate_X0(JsonParameterSet params) throws Throwable {
+        performTest(params);
+    }
+
+    @ParameterizedTest
+    @JsonParameterSetTest(value = "PeanoMultiplyExpression_XY.json")
+    public void testEvaluate_XY(JsonParameterSet params) throws Throwable {
+        performTest(params);
+    }
+
+    private static void performTest(JsonParameterSet params) throws Throwable {
+        int x = params.getInt("x");
+        int y = params.getInt("y");
+        int expected = params.getInt("expected");
+
+        Object xPeano = NumberConverter.toPeanoNumberExpression(x);
+        Object yPeano = NumberConverter.toPeanoNumberExpression(y);
+
+        Object mock = mock(PEANO_MULTIPLY_EXPRESSION.getLink().reflection(), CALLS_REAL_METHODS);
+        Object returned = PEANO_ARITHMETIC_EXPRESSION_EVALUATE.invoke(mock.getClass(), mock, xPeano, yPeano);
+
+        Object actualPeano = PEANO_NUMBER_EXPRESSION_EVALUATE.invoke(returned.getClass(), returned);
+
+        int actual = NumberConverter.toNaturalNumber(actualPeano);
+
+        assertEquals(
+            expected,
+            actual,
+            params.toContext("expected"),
+            r -> "Value returned by PeanoMultiplyExpression does not match expected."
+        );
+    }
+
+    @Test
+    public void testEvaluateRequirements() {
+        CtMethod<?> evaluate =
+            ((BasicMethodLink) PEANO_ARITHMETIC_EXPRESSION_EVALUATE.getLink(
+                PEANO_MULTIPLY_EXPRESSION.getLink().reflection(),
+                PEANO_NUMBER_EXPRESSION.getLink().reflection(),
+                PEANO_NUMBER_EXPRESSION.getLink().reflection()
+            )).getCtElement();
+
+        getCtElements(List.of(PEANO_MULTIPLY_EXPRESSION.getLink().reflection()), CtLambda.class, evaluate)
+            .forEach(ctLambda -> {
+                    String body = ctLambda.toStringDebug();
+                    Context context = contextBuilder().add("Lambda", body).build();
+
+                    Assertions2.assertNull(
+                        ctLambda.getBody(),
+                        context,
+                        r -> "evaluate() does not use correct lambdas."
+                    );
+                }
+            );
+    }
+}

solution/H07/src/graderPrivate/java/h07/PeanoNumberExpressionFactoryTest.java

@@ -0,0 +1,153 @@
+package h07;
+
+import org.junit.jupiter.params.ParameterizedTest;
+import org.sourcegrade.jagr.api.rubric.TestForSubmission;
+import org.tudalgo.algoutils.tutor.general.assertions.Context;
+import org.tudalgo.algoutils.tutor.general.json.JsonParameterSet;
+import org.tudalgo.algoutils.tutor.general.json.JsonParameterSetTest;
+import org.tudalgo.algoutils.tutor.general.match.BasicStringMatchers;
+import org.tudalgo.algoutils.tutor.general.reflections.BasicTypeLink;
+import org.tudalgo.algoutils.tutor.general.reflections.MethodLink;
+
+import java.lang.reflect.Array;
+import java.util.ArrayList;
+import java.util.List;
+
+import static h07.ClassReference.NUMBER_EXPRESSION;
+import static h07.ClassReference.PEANO_ARITHMETIC_EXPRESSION;
+import static h07.ClassReference.PEANO_NUMBER_EXPRESSION;
+import static h07.MethodReference.NUMBER_EXPRESSION_EVALUATE;
+import static h07.MethodReference.PEANO_ARITHMETIC_EXPRESSION_EVALUATE;
+import static h07.MethodReference.PEANO_NUMBER_EXPRESSION_EVALUATE;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+import static org.tudalgo.algoutils.tutor.general.assertions.Assertions2.*;
+
+@TestForSubmission
+public class PeanoNumberExpressionFactoryTest {
+
+    @ParameterizedTest
+    @JsonParameterSetTest(value = "PeanoNumberExpressionFactory_empty.json")
+    public void fold_empty(JsonParameterSet params) throws Throwable {
+        performTest(params);
+    }
+
+    @ParameterizedTest
+    @JsonParameterSetTest(value = "PeanoNumberExpressionFactory_filled.json")
+    public void fold_filled(JsonParameterSet params) throws Throwable {
+        performTest(params);
+    }
+
+    private static void performTest(JsonParameterSet params) throws Throwable {
+        List<Integer> inputs = new ArrayList<>();
+        params.getRootNode().get("inputs").forEach(value -> inputs.add(value.intValue()));
+        int initial = params.getInt("initial");
+        String operation = params.getString("operation");
+
+        int expected = params.getInt("expected");
+
+        List<Object> peanoInputs = new ArrayList<>();
+        inputs.forEach(input -> {
+            Object expression = null;
+            try {
+                expression = NumberConverter.toPeanoNumberExpression(input);
+            } catch (Throwable e) {
+                throw new RuntimeException(e);
+            }
+            peanoInputs.add(expression);
+        });
+
+        Object initialPeano = NumberConverter.toPeanoNumberExpression(initial);
+
+        Object peanoOperation = mock(PEANO_ARITHMETIC_EXPRESSION.getLink().reflection());
+        when(PEANO_ARITHMETIC_EXPRESSION_EVALUATE.invoke(
+            peanoOperation.getClass(),
+            peanoOperation,
+            any(),
+            any()
+        )).thenAnswer(mock -> {
+            Object peanoVal1 = mock.getArgument(0);
+            Object peanoVal2 = mock.getArgument(1);
+
+            int val1 = NumberConverter.toNaturalNumber(PEANO_NUMBER_EXPRESSION_EVALUATE.invoke(peanoVal1.getClass(), peanoVal1));
+            int val2 = NumberConverter.toNaturalNumber(PEANO_NUMBER_EXPRESSION_EVALUATE.invoke(peanoVal2.getClass(), peanoVal2));
+
+            int result = switch (operation) {
+                case "+" -> val1 + val2;
+                case "*" -> val1 * val2;
+                case "*2*" -> val1 * 2 * val2;
+                default -> 0;
+            };
+
+            return NumberConverter.toPeanoNumberExpression(result);
+        });
+
+        MethodLink foldLink = BasicTypeLink.of(ClassReference.PEANO_NUMBER_EXPRESSION_FACTORY.getLink().reflection())
+            .getMethod(BasicStringMatchers.identical("fold"));
+
+        if (foldLink == null){
+            fail(emptyContext(), r -> "Could not find method PeanoNumberExpressionFactory.fold()");
+        }
+
+        Object actualPeano = foldLink.invokeStatic(
+                peanoInputs.toArray((Object[]) Array.newInstance(PEANO_NUMBER_EXPRESSION.getLink().reflection(), 0)),
+                initialPeano,
+                peanoOperation
+            );
+
+        assertNotNull(actualPeano, params.toContext(), r -> "Fold returned null.");
+        int actual =
+            NumberConverter.toNaturalNumber(PEANO_NUMBER_EXPRESSION_EVALUATE.invoke(actualPeano.getClass(), actualPeano));
+
+        assertEquals(expected, actual, params.toContext(), r -> "Returned value of fold does not match expected.");
+    }
+
+    @ParameterizedTest
+    @JsonParameterSetTest(value = "PeanoNumberExpressionFactory_fromNumber.json")
+    public void testFromNumberExpressions(JsonParameterSet params) throws Throwable {
+        List<Integer> inputs = new ArrayList<>();
+        params.getRootNode().get("inputs").forEach(value -> inputs.add(value.intValue()));
+
+        List<Integer> expected = new ArrayList<>();
+        params.getRootNode().get("expected").forEach(value -> expected.add(value.intValue()));
+
+        List<Object> baseNumbers = new ArrayList<>();
+        inputs.forEach(input -> {
+            Object expression = mock(NUMBER_EXPRESSION.getLink().reflection());
+            try {
+                when(NUMBER_EXPRESSION_EVALUATE.invoke(NUMBER_EXPRESSION.getLink().reflection(), expression)).thenReturn(input);
+            } catch (Throwable e) {
+                throw new RuntimeException(e);
+            }
+            baseNumbers.add(expression);
+        });
+
+        MethodLink fromNumberExpressionsLink = BasicTypeLink.of(ClassReference.PEANO_NUMBER_EXPRESSION_FACTORY.getLink().reflection())
+            .getMethod(BasicStringMatchers.identical("fromNumberExpressions"));
+
+        if (fromNumberExpressionsLink == null){
+            fail(emptyContext(), r -> "Could not find method PeanoNumberExpressionFactory.fromNumberExpressions()");
+        }
+
+        List<Object> actualExpressions = List.of(
+            fromNumberExpressionsLink.invokeStatic(
+                (Object) baseNumbers.toArray((Object[]) Array.newInstance(NUMBER_EXPRESSION.getLink().reflection(), 0))
+            )
+        );
+        List<Integer> actual = actualExpressions.stream().map(expr -> {
+            try {
+                return NumberConverter.toNaturalNumber(PEANO_NUMBER_EXPRESSION_EVALUATE.invoke(expr.getClass(), expr));
+            } catch (Throwable e) {
+                throw new RuntimeException(e);
+            }
+        }).toList();
+
+        Context context = contextBuilder()
+            .add("inputs", inputs)
+            .add("expected", expected)
+            .build();
+
+        assertEquals(expected, actual, context, r -> "Returned List of expressions does not match expected list.");
+    }
+}

solution/H07/src/graderPrivate/java/h07/PeanoNumberExpressionTest.java

@@ -0,0 +1,25 @@
+package h07;
+
+import org.junit.jupiter.api.Test;
+import org.sourcegrade.jagr.api.rubric.TestForSubmission;
+
+@TestForSubmission
+public class PeanoNumberExpressionTest {
+
+    @Test
+    public void testDefinition() {
+        ClassReference.PEANO_NUMBER_EXPRESSION.assertCorrectlyDefined();
+        MethodReference.PEANO_NUMBER_EXPRESSION_EVALUATE.assertCorrectlyDefined();
+    }
+
+    @Test
+    public void testNaming() {
+        ClassReference.PEANO_NUMBER_EXPRESSION.assertNamedCorrectly();
+        MethodReference.PEANO_NUMBER_EXPRESSION_EVALUATE.assertNamedCorrectly();
+    }
+
+    @Test
+    public void testPackage() {
+        ClassReference.PEANO_NUMBER_EXPRESSION.assertDefinedInCorrectPackage();
+    }
+}

solution/H07/src/graderPrivate/java/h07/Tests.java

@@ -0,0 +1,52 @@
+package h07;
+
+import org.tudalgo.algoutils.tutor.general.match.BasicStringMatchers;
+import org.tudalgo.algoutils.tutor.general.match.Match;
+import org.tudalgo.algoutils.tutor.general.match.Matcher;
+import org.tudalgo.algoutils.tutor.general.match.MatcherFactories;
+import org.tudalgo.algoutils.tutor.general.match.Stringifiable;
+
+public class Tests {
+
+    private static final double MINIMUM_SIMILARITY = .75;
+
+    private static final MatcherFactories.StringMatcherFactory STRING_MATCHER_FACTORY = BasicStringMatchers::identical;
+
+    @SuppressWarnings("removal")
+    public static <T extends Stringifiable> Matcher<T> stringMatcher(String string) {
+
+        return new Matcher<T>() {
+
+            @Override
+            public <ST extends T> Match<ST> match(ST object) {
+                return new Match<>() {
+
+                    final double similarity =
+                        org.tudalgo.algoutils.reflect.TestUtils.similarity(object.string(), string);
+
+                    @Override
+                    public boolean matched() {
+                        return similarity >= MINIMUM_SIMILARITY;
+                    }
+
+                    @Override
+                    public ST object() {
+                        return object;
+                    }
+
+                    @Override
+                    public int compareTo(Match<ST> other) {
+                        if (!other.matched()) {
+                            return matched() ? 1 : 0;
+                        } else if (!matched()) {
+                            return -1;
+                        }
+                        double otherSimilarity =
+                            org.tudalgo.algoutils.reflect.TestUtils.similarity(other.object().string(), string);
+                        return Double.compare(similarity, otherSimilarity);
+                    }
+                };
+            }
+        };
+    }
+}

solution/H07/src/graderPrivate/resources/h07/ConvertNumberToPeanoExpressionImpl_0.json

@@ -0,0 +1,5 @@
+[
+  {
+    "x": "0"
+  }
+]

solution/H07/src/graderPrivate/resources/h07/ConvertNumberToPeanoExpressionImpl_X.json

@@ -0,0 +1,26 @@
+[
+  {
+    "x": "1"
+  },
+  {
+    "x": "3"
+  },
+  {
+    "x": "7"
+  },
+  {
+    "x": "10"
+  },
+  {
+    "x": "25"
+  },
+  {
+    "x": "30"
+  },
+  {
+    "x": "99"
+  },
+  {
+    "x": "6"
+  }
+]

solution/H07/src/graderPrivate/resources/h07/ConvertPeanoToNumberExpressionImpl_0.json

@@ -0,0 +1,5 @@
+[
+  {
+    "x": "0"
+  }
+]

solution/H07/src/graderPrivate/resources/h07/ConvertPeanoToNumberExpressionImpl_X.json

@@ -0,0 +1,26 @@
+[
+  {
+    "x": "1"
+  },
+  {
+    "x": "3"
+  },
+  {
+    "x": "7"
+  },
+  {
+    "x": "10"
+  },
+  {
+    "x": "25"
+  },
+  {
+    "x": "30"
+  },
+  {
+    "x": "99"
+  },
+  {
+    "x": "6"
+  }
+]

solution/H07/src/graderPrivate/resources/h07/NumberExpressionFactory_filter_complex.json

@@ -0,0 +1,37 @@
+[
+  {
+    "inputs": [1,2,3,4,5,6,7,8,9],
+    "filter": [true, false, true, false, true, false, true, false, true],
+    "expected": [1,3,5,7,9]
+  },
+  {
+    "inputs": [1,2,3,4,6,7,8,9],
+    "filter": [true, true, true, false, false, true, true, true],
+    "expected": [1,2,3,7,8,9]
+  },
+  {
+    "inputs": [1,2,3,4,5],
+    "filter": [true, false, true, true, true],
+    "expected": [1,3,4,5]
+  },
+  {
+    "inputs": [2,4,6,8,10],
+    "filter": [true, true, true, true, false],
+    "expected": [2,4,6,8]
+  },
+  {
+    "inputs": [1,2,3,4,5,6,7,8,9],
+    "filter": [true, true, true, false, true, true, true, true, true],
+    "expected": [1,2,3,5,6,7,8,9]
+  },
+  {
+    "inputs": [1,2,3,4,5,6,7,8,9],
+    "filter": [false, true, true, true, true, true, true, true, true],
+    "expected": [2,3,4,5,6,7,8,9]
+  },
+  {
+    "inputs": [1,2,3,4,5,6,7,8,9],
+    "filter": [true, true, true, true, true, true, true, true, false],
+    "expected": [1,2,3,4,5,6,7,8]
+  }
+]

solution/H07/src/graderPrivate/resources/h07/NumberExpressionFactory_filter_empty.json

@@ -0,0 +1,7 @@
+[
+  {
+    "inputs": [],
+    "filter": [],
+    "expected": []
+  }
+]

solution/H07/src/graderPrivate/resources/h07/NumberExpressionFactory_filter_false.json

@@ -0,0 +1,22 @@
+[
+  {
+    "inputs": [1,2,3,4,5,6,7,8,9],
+    "filter": [false, false, false, false, false, false, false, false, false],
+    "expected": []
+  },
+  {
+    "inputs": [1,2,3,4,6,7,8,9],
+    "filter": [false, false, false, false, false, false, false, false],
+    "expected": []
+  },
+  {
+    "inputs": [1,2,3,4,5],
+    "filter": [false, false, false, false, false],
+    "expected": []
+  },
+  {
+    "inputs": [2,4,6,8,10],
+    "filter": [false, false, false, false, false],
+    "expected": []
+  }
+]

solution/H07/src/graderPrivate/resources/h07/NumberExpressionFactory_filter_true.json

@@ -0,0 +1,22 @@
+[
+  {
+    "inputs": [1,2,3,4,5,6,7,8,9],
+    "filter": [true, true, true, true, true, true, true, true, true],
+    "expected": [1,2,3,4,5,6,7,8,9]
+  },
+  {
+    "inputs": [1,2,3,4,6,7,8,9],
+    "filter": [true, true, true, true, true, true, true, true],
+    "expected": [1,2,3,4,6,7,8,9]
+  },
+  {
+    "inputs": [1,2,3,4,5],
+    "filter": [true, true, true, true, true],
+    "expected": [1,2,3,4,5]
+  },
+  {
+    "inputs": [2,4,6,8,10],
+    "filter": [true, true, true, true, true],
+    "expected": [2,4,6,8,10]
+  }
+]

solution/H07/src/graderPrivate/resources/h07/NumberExpressionFactory_multiply_Complex.json

@@ -0,0 +1,44 @@
+[
+  {
+    "lowerBound": "1",
+    "upperBound": "3",
+    "expected": [
+      1, 2, 3, 2, 4, 6, 3, 6, 9
+    ]
+  },
+  {
+    "lowerBound": "2",
+    "upperBound": "5",
+    "expected": [
+      4, 6, 8, 10, 6, 9, 12, 15, 8, 12, 16, 20, 10, 15, 20, 25
+    ]
+  },
+  {
+    "lowerBound": "3",
+    "upperBound": "10",
+    "expected": [
+      9, 12, 15, 18, 21, 24, 27, 30, 12, 16, 20, 24, 28, 32, 36, 40, 15, 20, 25, 30, 35, 40, 45, 50, 18, 24, 30, 36, 42, 48, 54, 60, 21, 28, 35, 42, 49, 56, 63, 70, 24, 32, 40, 48, 56, 64, 72, 80, 27, 36, 45, 54, 63, 72, 81, 90, 30, 40, 50, 60, 70, 80, 90, 100
+    ]
+  },
+  {
+    "lowerBound": "1",
+    "upperBound": "9",
+    "expected": [
+      1, 2, 3, 4, 5, 6, 7, 8, 9, 2, 4, 6, 8, 10, 12, 14, 16, 18, 3, 6, 9, 12, 15, 18, 21, 24, 27, 4, 8, 12, 16, 20, 24, 28, 32, 36, 5, 10, 15, 20, 25, 30, 35, 40, 45, 6, 12, 18, 24, 30, 36, 42, 48, 54, 7, 14, 21, 28, 35, 42, 49, 56, 63, 8, 16, 24, 32, 40, 48, 56, 64, 72, 9, 18, 27, 36, 45, 54, 63, 72, 81
+    ]
+  },
+  {
+    "lowerBound": "5",
+    "upperBound": "7",
+    "expected": [
+      25, 30, 35, 30, 36, 42, 35, 42, 49
+    ]
+  },
+  {
+    "lowerBound": "1",
+    "upperBound": "2",
+    "expected": [
+      1, 2, 2, 4
+    ]
+  }
+]

solution/H07/src/graderPrivate/resources/h07/NumberExpressionFactory_multiply_Simple.json

@@ -0,0 +1,37 @@
+[
+  {
+    "lowerBound": "2",
+    "upperBound": "2",
+    "expected": [
+      4
+    ]
+  },
+  {
+    "lowerBound": "1",
+    "upperBound": "1",
+    "expected": [
+      1
+    ]
+  },
+  {
+    "lowerBound": "3",
+    "upperBound": "3",
+    "expected": [
+      9
+    ]
+  },
+  {
+    "lowerBound": "6",
+    "upperBound": "6",
+    "expected": [
+      36
+    ]
+  },
+  {
+    "lowerBound": "10",
+    "upperBound": "10",
+    "expected": [
+      100
+    ]
+  }
+]

solution/H07/src/graderPrivate/resources/h07/PeanoAddExpression_0X.json

@@ -0,0 +1,27 @@
+[
+  {
+    "x": "0",
+    "y": "1",
+    "expected": "1"
+  },
+  {
+    "x": "0",
+    "y": "2",
+    "expected": "2"
+  },
+  {
+    "x": "0",
+    "y": "3",
+    "expected": "3"
+  },
+  {
+    "x": "0",
+    "y": "5",
+    "expected": "5"
+  },
+  {
+    "x": "0",
+    "y": "9",
+    "expected": "9"
+  }
+]

solution/H07/src/graderPrivate/resources/h07/PeanoAddExpression_X0.json

@@ -0,0 +1,27 @@
+[
+  {
+    "x": "1",
+    "y": "0",
+    "expected": "1"
+  },
+  {
+    "x": "2",
+    "y": "0",
+    "expected": "2"
+  },
+  {
+    "x": "3",
+    "y": "0",
+    "expected": "3"
+  },
+  {
+    "x": "5",
+    "y": "0",
+    "expected": "5"
+  },
+  {
+    "x": "9",
+    "y": "0",
+    "expected": "9"
+  }
+]

solution/H07/src/graderPrivate/resources/h07/PeanoAddExpression_XY.json

@@ -0,0 +1,42 @@
+[
+  {
+    "x": "1",
+    "y": "1",
+    "expected": "2"
+  },
+  {
+    "x": "2",
+    "y": "2",
+    "expected": "4"
+  },
+  {
+    "x": "3",
+    "y": "3",
+    "expected": "6"
+  },
+  {
+    "x": "5",
+    "y": "5",
+    "expected": "10"
+  },
+  {
+    "x": "9",
+    "y": "9",
+    "expected": "18"
+  },
+  {
+    "x": "1",
+    "y": "4",
+    "expected": "5"
+  },
+  {
+    "x": "3",
+    "y": "6",
+    "expected": "9"
+  },
+  {
+    "x": "2",
+    "y": "7",
+    "expected": "9"
+  }
+]

solution/H07/src/graderPrivate/resources/h07/PeanoMultiplyExpression_0X.json

@@ -0,0 +1,27 @@
+[
+  {
+    "x": "0",
+    "y": "1",
+    "expected": "0"
+  },
+  {
+    "x": "0",
+    "y": "2",
+    "expected": "0"
+  },
+  {
+    "x": "0",
+    "y": "3",
+    "expected": "0"
+  },
+  {
+    "x": "0",
+    "y": "5",
+    "expected": "0"
+  },
+  {
+    "x": "0",
+    "y": "9",
+    "expected": "0"
+  }
+]

solution/H07/src/graderPrivate/resources/h07/PeanoMultiplyExpression_X0.json

@@ -0,0 +1,27 @@
+[
+  {
+    "x": "1",
+    "y": "0",
+    "expected": "0"
+  },
+  {
+    "x": "2",
+    "y": "0",
+    "expected": "0"
+  },
+  {
+    "x": "3",
+    "y": "0",
+    "expected": "0"
+  },
+  {
+    "x": "5",
+    "y": "0",
+    "expected": "0"
+  },
+  {
+    "x": "9",
+    "y": "0",
+    "expected": "0"
+  }
+]

solution/H07/src/graderPrivate/resources/h07/PeanoMultiplyExpression_XY.json

@@ -0,0 +1,42 @@
+[
+  {
+    "x": "1",
+    "y": "1",
+    "expected": "1"
+  },
+  {
+    "x": "2",
+    "y": "2",
+    "expected": "4"
+  },
+  {
+    "x": "3",
+    "y": "3",
+    "expected": "9"
+  },
+  {
+    "x": "5",
+    "y": "5",
+    "expected": "25"
+  },
+  {
+    "x": "9",
+    "y": "9",
+    "expected": "81"
+  },
+  {
+    "x": "1",
+    "y": "4",
+    "expected": "4"
+  },
+  {
+    "x": "3",
+    "y": "6",
+    "expected": "18"
+  },
+  {
+    "x": "2",
+    "y": "7",
+    "expected": "14"
+  }
+]

solution/H07/src/graderPrivate/resources/h07/PeanoNumberExpressionFactory_empty.json

@@ -0,0 +1,26 @@
+[
+  {
+    "inputs": [
+
+    ],
+    "initial": "5",
+    "operation": "+",
+    "expected": "5"
+  },
+  {
+    "inputs": [
+
+    ],
+    "initial": "10",
+    "operation": "*",
+    "expected": "10"
+  },
+  {
+    "inputs": [
+
+    ],
+    "initial": "2",
+    "operation": "*2*",
+    "expected": "2"
+  }
+]

solution/H07/src/graderPrivate/resources/h07/PeanoNumberExpressionFactory_filled.json

@@ -0,0 +1,34 @@
+[
+  {
+    "inputs": [
+      1,2,3,4
+    ],
+    "initial": "0",
+    "operation": "+",
+    "expected": "10"
+  },
+  {
+    "inputs": [
+      2,3,4,5
+    ],
+    "initial": "1",
+    "operation": "*",
+    "expected": "120"
+  },
+  {
+    "inputs": [
+      2,3,4,5
+    ],
+    "initial": "0",
+    "operation": "*",
+    "expected": "0"
+  },
+  {
+    "inputs": [
+      2,4,6
+    ],
+    "initial": "2",
+    "operation": "*2*",
+    "expected": "768"
+  }
+]

solution/H07/src/graderPrivate/resources/h07/PeanoNumberExpressionFactory_fromNumber.json

@@ -0,0 +1,42 @@
+[
+  {
+    "inputs": [
+      1,2,3,4
+    ],
+    "expected": [
+      1,2,3,4
+    ]
+  },
+  {
+    "inputs": [
+      2,3,4,5
+    ],
+    "expected": [
+      2,3,4,5
+    ]
+  },
+  {
+    "inputs": [
+      2,3,4,5,6
+    ],
+    "expected": [
+      2,3,4,5,6
+    ]
+  },
+  {
+    "inputs": [
+      2,4,6
+    ],
+    "expected": [
+      2,4,6
+    ]
+  },
+  {
+    "inputs": [
+      100,5,0
+    ],
+    "expected": [
+      100,5,0
+    ]
+  }
+]

solution/H07/src/main/java/h07/ArithmeticExpression.java

@@ -0,0 +1,18 @@
+package h07;
+
+import org.tudalgo.algoutils.student.annotation.StudentCreationRequired;
+
+/**
+ * Represents an arithmetic operation on numbers.
+ */
+@StudentCreationRequired
+public interface ArithmeticExpression {
+    /**
+     * Applies the arithmetic operation to the two numbers.
+     *
+     * @param num1 the first number
+     * @param num2 the second number
+     * @return the result of the operation
+     */
+    NumberExpression evaluate(NumberExpression num1, NumberExpression num2);
+}

solution/H07/src/main/java/h07/ConvertNumberToPeanoExpression.java

@@ -0,0 +1,18 @@
+package h07;
+
+import h07.peano.PeanoNumberExpression;
+import org.tudalgo.algoutils.student.annotation.StudentCreationRequired;
+
+/**
+ * Converts a number expression to a Peano number expression.
+ */
+@StudentCreationRequired
+public interface ConvertNumberToPeanoExpression {
+    /**
+     * Converts a number expression to a Peano number expression.
+     *
+     * @param numberExpression the number expression to convert
+     * @return the Peano number expression
+     */
+    PeanoNumberExpression convert(NumberExpression numberExpression);
+}

solution/H07/src/main/java/h07/ConvertNumberToPeanoExpressionImpl.java

@@ -0,0 +1,23 @@
+package h07;
+
+import h07.peano.PeanoNumberExpression;
+import h07.peano.Zero;
+import h07.peano.Successor;
+import org.tudalgo.algoutils.student.annotation.StudentCreationRequired;
+
+/**
+ * Converts a number expression to a Peano number expression.
+ */
+@StudentCreationRequired
+public class ConvertNumberToPeanoExpressionImpl implements ConvertNumberToPeanoExpression {
+    @Override
+    public PeanoNumberExpression convert(NumberExpression numberExpression) {
+        int value = numberExpression.evaluate();
+
+        if (value == 0) {
+            return Zero::new;
+        } else {
+            return () -> new Successor(new ConvertNumberToPeanoExpressionImpl().convert(() -> value - 1).evaluate());
+        }
+    }
+}

solution/H07/src/main/java/h07/ConvertPeanoToNumberExpression.java

@@ -0,0 +1,18 @@
+package h07;
+
+import h07.peano.PeanoNumberExpression;
+import org.tudalgo.algoutils.student.annotation.StudentCreationRequired;
+
+/**
+ * Converts a Peano number expression to a number expression.
+ */
+@StudentCreationRequired
+public interface ConvertPeanoToNumberExpression {
+    /**
+     * Converts a Peano number expression to a number expression.
+     *
+     * @param peanoNumberExpression the Peano number expression to convert
+     * @return the number expression
+     */
+    NumberExpression convert(PeanoNumberExpression peanoNumberExpression);
+}

solution/H07/src/main/java/h07/ConvertPeanoToNumberExpressionImpl.java

@@ -0,0 +1,23 @@
+package h07;
+
+import h07.peano.NaturalNumber;
+import h07.peano.PeanoNumberExpression;
+import h07.peano.Successor;
+import org.tudalgo.algoutils.student.annotation.StudentCreationRequired;
+
+/**
+ * Converts a Peano number expression to a number expression.
+ */
+@StudentCreationRequired
+public class ConvertPeanoToNumberExpressionImpl implements ConvertPeanoToNumberExpression {
+    @Override
+    public NumberExpression convert(PeanoNumberExpression peanoNumberExpression) {
+        NaturalNumber naturalNumber = peanoNumberExpression.evaluate();
+
+        if (naturalNumber instanceof Successor successor) {
+            return () -> new ConvertPeanoToNumberExpressionImpl().convert(() -> successor.predecessor).evaluate() + 1;
+        } else {
+            return () -> 0;
+        }
+    }
+}

solution/H07/src/main/java/h07/Main.java

@@ -0,0 +1,78 @@
+package h07;
+
+import h07.peano.*;
+import org.tudalgo.algoutils.student.annotation.DoNotTouch;
+import org.tudalgo.algoutils.student.annotation.StudentImplementationRequired;
+
+/**
+ * Main entry point in executing the program.
+ */
+public class Main {
+    /**
+     * Main entry point in executing the program.
+     *
+     * @param args program arguments, currently ignored
+     */
+    public static void main(String[] args) {
+        testHeader("Multiplication Table");
+        numberExpressionMultiplicationTableTests();
+
+        testHeader("Peano Number Expressions");
+        peanoNumberExpressionTests();
+
+        testHeader("Filter, Fold, Map");
+        filterFoldMapTests();
+    }
+
+    @DoNotTouch
+    private static void testHeader(String testName) {
+        System.out.println("-----------------------------------");
+        System.out.println("Running test: " + testName);
+        System.out.println("-----------------------------------");
+    }
+
+    @DoNotTouch
+    private static void numberExpressionMultiplicationTableTests() {
+        int lowerBound = 1;
+        int upperBound = 10;
+        NumberExpression[] multiplicationTable = NumberExpressionFactory.multiplicationTable(lowerBound, upperBound);
+
+        for (int i = lowerBound; i <= upperBound; i++) {
+            for (int j = lowerBound; j <= upperBound; j++) {
+                System.out.printf("| %4s ", multiplicationTable[(i - lowerBound) * (upperBound - lowerBound + 1) + (j - lowerBound)].evaluate());
+            }
+            System.out.println("|");
+        }
+    }
+
+    private static final NaturalNumber THREE = new Successor(new Successor(new Successor(new Zero())));
+    private static final NaturalNumber SEVEN = new Successor(new Successor(new Successor(new Successor(new Successor(new Successor(new Successor(new Zero())))))));
+
+    @StudentImplementationRequired
+    private static void peanoNumberExpressionTests() {
+        PeanoNumberExpression three = () -> THREE;
+        PeanoNumberExpression seven = () -> SEVEN;
+
+        PeanoNumberExpression sum = new PeanoAddExpression().evaluate(three, seven);
+        PeanoNumberExpression product = new PeanoMultiplyExpression().evaluate(three, seven);
+
+        System.out.println(sum.evaluate());
+        System.out.println(product.evaluate());
+
+        // Not required but can be used to convert Peano numbers to integers
+        System.out.println(new ConvertPeanoToNumberExpressionImpl().convert(sum).evaluate());
+        System.out.println(new ConvertPeanoToNumberExpressionImpl().convert(product).evaluate());
+    }
+
+    @StudentImplementationRequired
+    private static void filterFoldMapTests() {
+        NumberExpression[] numbers = NumberExpressionFactory.multiplicationTable(1, 10);
+        NumberExpression[] filteredNumbers = NumberExpressionFactory.filter(numbers, n -> n % 3 == 0);
+        PeanoNumberExpression[] filteredPeanoNumbers = PeanoNumberExpressionFactory
+                .fromNumberExpressions(filteredNumbers);
+        PeanoNumberExpression foldedPeanoNumbers = PeanoNumberExpressionFactory.fold(filteredPeanoNumbers, Zero::new,
+                new PeanoAddExpression());
+        int foldedNumber = new ConvertPeanoToNumberExpressionImpl().convert(foldedPeanoNumbers).evaluate();
+        System.out.println(foldedNumber);
+    }
+}

solution/H07/src/main/java/h07/NumberExpression.java

@@ -0,0 +1,16 @@
+package h07;
+
+import org.tudalgo.algoutils.student.annotation.StudentCreationRequired;
+
+/**
+ * Represents a number expression.
+ */
+@StudentCreationRequired
+public interface NumberExpression {
+    /**
+     * Evaluates the expression represented by this node.
+     *
+     * @return the result of the evaluation
+     */
+    int evaluate();
+}

solution/H07/src/main/java/h07/NumberExpressionFactory.java

@@ -0,0 +1,89 @@
+package h07;
+
+import java.util.function.IntPredicate;
+
+import org.tudalgo.algoutils.student.annotation.DoNotTouch;
+import org.tudalgo.algoutils.student.annotation.StudentImplementationRequired;
+
+/**
+ * A factory class for creating number expressions.
+ */
+public class NumberExpressionFactory {
+    /**
+     * Calculates the product of all possible pairs of numbers in the given array.
+     *
+     * @param numbers the array of number expressions to calculate the multiplication table
+     * @return An array of number expressions representing the result of the
+     *         multiplication table of the given numbers.
+     */
+    @StudentImplementationRequired
+    public static NumberExpression[] multiplicationTable(NumberExpression[] numbers) {
+        NumberExpression[] multiplicationTable = new NumberExpression[numbers.length * numbers.length];
+
+        ArithmeticExpression multiplication = (num1, num2) -> {
+            return () -> num1.evaluate() * num2.evaluate();
+        };
+
+        for (int i = 0; i < numbers.length; i++) {
+            for (int j = 0; j < numbers.length; j++) {
+                multiplicationTable[i * numbers.length + j] = multiplication.evaluate(numbers[i], numbers[j]);
+            }
+        }
+
+        return multiplicationTable;
+    }
+
+    /**
+     * Calculates the product of all possible pairs of numbers in the given range.
+     *
+     * @param lowerBound the lower bound of the multiplication table, inclusive
+     * @param upperBound the upper bound of the multiplication table, inclusive
+     * @return An array of number expressions representing the result of the
+     *         multiplication table of the numbers from lowerBound to upperBound.
+     */
+    @DoNotTouch
+    public static NumberExpression[] multiplicationTable(int lowerBound, int upperBound) {
+        int numberOfNumbers = upperBound - lowerBound + 1;
+        NumberExpression[] baseNumbers = new NumberExpression[numberOfNumbers];
+
+        for (int i = lowerBound; i <= upperBound; i++) {
+            // Copy to local variable to make it effectively final, so it can be used in
+            // lambda
+            int finalI = i;
+            baseNumbers[i - lowerBound] = () -> finalI;
+        }
+
+        return multiplicationTable(baseNumbers);
+    }
+
+    /**
+     * Filters the given array of number expressions based on the given predicate.
+     * The returned array should contain only the number expressions that satisfy
+     * the predicate in the same order as they appear in the input array.
+     * This means there should be no null values in the returned array.
+     *
+     * @param numbers   the array of number expressions to filter
+     * @param predicate the predicate to filter the number expressions
+     * @return An array of number expressions that satisfy the predicate.
+     */
+    @StudentImplementationRequired
+    public static NumberExpression[] filter(NumberExpression[] numbers, IntPredicate predicate) {
+        int count = 0;
+        for (NumberExpression number : numbers) {
+            if (predicate.test(number.evaluate())) {
+                count++;
+            }
+        }
+
+        NumberExpression[] result = new NumberExpression[count];
+
+        int nextIndex = 0;
+        for (NumberExpression number : numbers) {
+            if (predicate.test(number.evaluate())) {
+                result[nextIndex++] = number;
+            }
+        }
+
+        return result;
+    }
+}

solution/H07/src/main/java/h07/peano/NaturalNumber.java

@@ -0,0 +1,17 @@
+package h07.peano;
+
+import org.tudalgo.algoutils.student.annotation.DoNotTouch;
+
+/**
+ * Represents a natural number.
+ */
+@DoNotTouch
+public abstract class NaturalNumber {
+    /**
+     * Returns the string representation of the natural number.
+     *
+     * @return the string representation of the natural number
+     */
+    @Override
+    public abstract String toString();
+}

solution/H07/src/main/java/h07/peano/PeanoAddExpression.java

@@ -0,0 +1,27 @@
+package h07.peano;
+
+import org.tudalgo.algoutils.student.annotation.StudentCreationRequired;
+
+/**
+ * Represents an addition operation in Peano arithmetic.
+ */
+@StudentCreationRequired
+public class PeanoAddExpression implements PeanoArithmeticExpression {
+    @Override
+    public PeanoNumberExpression evaluate(PeanoNumberExpression num1, PeanoNumberExpression num2) {
+        NaturalNumber naturalNumber1 = num1.evaluate();
+
+        if (naturalNumber1 instanceof Successor naturalNumber1Peano) {
+            return () -> {
+                return new Successor(
+                    new PeanoAddExpression().evaluate(
+                        () -> { return naturalNumber1Peano.predecessor; },
+                        num2
+                    ).evaluate()
+                );
+            };
+        } else {
+            return num2;
+        }
+    }
+}

solution/H07/src/main/java/h07/peano/PeanoArithmeticExpression.java

@@ -0,0 +1,18 @@
+package h07.peano;
+
+import org.tudalgo.algoutils.student.annotation.StudentCreationRequired;
+
+/**
+ * Represents an arithmetic operation in Peano arithmetic.
+ */
+@StudentCreationRequired
+public interface PeanoArithmeticExpression {
+    /**
+     * Evaluates the expression represented by this node.
+     *
+     * @param num1 the first number to evaluate
+     * @param num2 the second number to evaluate
+     * @return the result of the evaluation
+     */
+    PeanoNumberExpression evaluate(PeanoNumberExpression num1, PeanoNumberExpression num2);
+}

solution/H07/src/main/java/h07/peano/PeanoMultiplyExpression.java

@@ -0,0 +1,29 @@
+package h07.peano;
+
+import org.tudalgo.algoutils.student.annotation.StudentCreationRequired;
+
+/**
+ * Represents a multiplication operation in Peano arithmetic.
+ */
+@StudentCreationRequired
+public class PeanoMultiplyExpression implements PeanoArithmeticExpression {
+    @Override
+    public PeanoNumberExpression evaluate(PeanoNumberExpression num1, PeanoNumberExpression num2) {
+        NaturalNumber naturalNumber2 = num2.evaluate();
+
+        if (naturalNumber2 instanceof Successor naturalNumber2Peano) {
+            if (naturalNumber2Peano.predecessor instanceof Zero) {
+                return num1;
+            } else {
+                return () -> new PeanoAddExpression().evaluate(
+                        num1,
+                        new PeanoMultiplyExpression().evaluate(
+                                num1,
+                                () -> naturalNumber2Peano.predecessor))
+                        .evaluate();
+            }
+        } else {
+            return Zero::new;
+        }
+    }
+}

solution/H07/src/main/java/h07/peano/PeanoNumberExpression.java

@@ -0,0 +1,16 @@
+package h07.peano;
+
+import org.tudalgo.algoutils.student.annotation.StudentCreationRequired;
+
+/**
+ * Represents a Peano number expression.
+ */
+@StudentCreationRequired
+public interface PeanoNumberExpression {
+    /**
+     * Evaluates the expression represented by this node.
+     *
+     * @return the result of the evaluation
+     */
+    NaturalNumber evaluate();
+}

solution/H07/src/main/java/h07/peano/PeanoNumberExpressionFactory.java

@@ -0,0 +1,44 @@
+package h07.peano;
+
+import h07.ConvertNumberToPeanoExpressionImpl;
+import h07.NumberExpression;
+import org.tudalgo.algoutils.student.annotation.StudentImplementationRequired;
+
+/**
+ * Represents a factory for Peano number expressions.
+ */
+public class PeanoNumberExpressionFactory {
+    /**
+     * Converts an array of number expressions to an array of Peano number expressions.
+     *
+     * @param numberExpressions the number expressions to convert
+     * @return the converted Peano number expressions
+     */
+    @StudentImplementationRequired
+    public static PeanoNumberExpression[] fromNumberExpressions(NumberExpression[] numberExpressions) {
+        PeanoNumberExpression[] peanoNumberExpressions = new PeanoNumberExpression[numberExpressions.length];
+
+        for (int i = 0; i < numberExpressions.length; i++) {
+            peanoNumberExpressions[i] = new ConvertNumberToPeanoExpressionImpl().convert(numberExpressions[i]);
+        }
+
+        return peanoNumberExpressions;
+    }
+
+    /**
+     * Folds an array of Peano number expressions into a single Peano number expression.
+     *
+     * @param peanoNumberExpressions the Peano number expressions to fold
+     * @param initial the initial Peano number expression
+     * @param operation the operation to apply
+     * @return the folded Peano number expression
+     */
+    @StudentImplementationRequired
+    public static PeanoNumberExpression fold(PeanoNumberExpression[] peanoNumberExpressions, PeanoNumberExpression initial, PeanoArithmeticExpression operation) {
+        PeanoNumberExpression result = initial;
+        for (PeanoNumberExpression peanoNumberExpression : peanoNumberExpressions) {
+            result = operation.evaluate(result, peanoNumberExpression);
+        }
+        return result;
+    }
+}

solution/H07/src/main/java/h07/peano/Successor.java

@@ -0,0 +1,20 @@
+package h07.peano;
+
+import org.tudalgo.algoutils.student.annotation.DoNotTouch;
+
+/**
+ * Represents a successor of a natural number in Peano arithmetic.
+ */
+@DoNotTouch
+public class Successor extends NaturalNumber {
+    public final NaturalNumber predecessor;
+
+    public Successor(NaturalNumber predecessor) {
+        this.predecessor = predecessor;
+    }
+
+    @Override
+    public String toString() {
+        return "S(" + predecessor.toString() + ")";
+    }
+}

solution/H07/src/main/java/h07/peano/Zero.java

@@ -0,0 +1,14 @@
+package h07.peano;
+
+import org.tudalgo.algoutils.student.annotation.DoNotTouch;
+
+/**
+ * Represents the number zero in Peano arithmetic.
+ */
+@DoNotTouch
+public class Zero extends NaturalNumber {
+    @Override
+    public String toString() {
+        return "Z";
+    }
+}

solution/H07/src/test/java/h07/ExampleJUnitTest.java

@@ -0,0 +1,16 @@
+package h07;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+/**
+ * An example JUnit test class.
+ */
+public class ExampleJUnitTest {
+
+    @Test
+    public void testAddition() {
+        assertEquals(2, 1 + 1);
+    }
+}

solution/H07/version

@@ -0,0 +1 @@
+0.1.0-SNAPSHOT