Merge commit '01bfe4430f5e6f27248d7e28879accc977293670' as 'H07'

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

H07/.gitignore

@@ -0,0 +1,86 @@
+### 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
+jagr.conf

H07/README.md

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

H07/build.gradle.kts

@@ -0,0 +1,33 @@
+import org.sourcegrade.jagr.gradle.task.grader.GraderRunTask
+
+plugins {
+    alias(libs.plugins.algomate)
+}
+
+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 = ""
+    firstName = ""
+    lastName = ""
+
+    // Optionally require own tests for mainBuildSubmission task. Default is false
+    requireTests = false
+}
+
+tasks {
+    withType<GraderRunTask> {
+        doFirst {
+            throw GradleException("No public tests are provided for this exercise! For more information go to https://moodle.informatik.tu-darmstadt.de/mod/page/view.php?id=68766")
+        }
+    }
+}

H07/gradle/libs.versions.toml

@@ -0,0 +1,2 @@
+[plugins]
+algomate = { id = "org.tudalgo.algomate", version = "0.7.1" }

H07/gradle/wrapper/gradle-wrapper.properties

@@ -0,0 +1,7 @@
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.10.2-all.zip
+networkTimeout=10000
+validateDistributionUrl=true
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists

H07/gradlew

@@ -0,0 +1,249 @@
+#!/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##*/}
+# Discard cd standard output in case $CDPATH is set (https://github.com/gradle/gradle/issues/25036)
+APP_HOME=$( cd "${APP_HOME:-./}" > /dev/null && pwd -P ) || exit
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD=maximum
+
+warn () {
+    echo "$*"
+} >&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: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+else
+    JAVACMD=java
+    if ! command -v java >/dev/null 2>&1
+    then
+        die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+fi
+
+# Increase the maximum file descriptors if we can.
+if ! "$cygwin" && ! "$darwin" && ! "$nonstop" ; then
+    case $MAX_FD in #(
+      max*)
+        # In POSIX sh, ulimit -H is undefined. That's why the result is checked to see if it worked.
+        # shellcheck disable=SC2039,SC3045
+        MAX_FD=$( ulimit -H -n ) ||
+            warn "Could not query maximum file descriptor limit"
+    esac
+    case $MAX_FD in  #(
+      '' | soft) :;; #(
+      *)
+        # In POSIX sh, ulimit -n is undefined. That's why the result is checked to see if it worked.
+        # shellcheck disable=SC2039,SC3045
+        ulimit -n "$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, JAVA_OPTS, and optsEnvironmentVar are not allowed to contain shell fragments,
+#     and any embedded shellness will be escaped.
+#   * For example: A user cannot expect ${Hostname} to be expanded, as it is an environment variable and will be
+#     treated as '${Hostname}' itself on the command line.
+
+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 "$JAVACMD" "$@"

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. 1>&2
+echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH. 1>&2
+echo. 1>&2
+echo Please set the JAVA_HOME variable in your environment to match the 1>&2
+echo location of your Java installation. 1>&2
+
+goto fail
+
+:findJavaFromJavaHome
+set JAVA_HOME=%JAVA_HOME:"=%
+set JAVA_EXE=%JAVA_HOME%/bin/java.exe
+
+if exist "%JAVA_EXE%" goto execute
+
+echo. 1>&2
+echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME% 1>&2
+echo. 1>&2
+echo Please set the JAVA_HOME variable in your environment to match the 1>&2
+echo location of your Java installation. 1>&2
+
+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

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-Student"

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

@@ -0,0 +1,66 @@
+package h07;
+
+import org.tudalgo.algoutils.student.annotation.DoNotTouch;
+import org.tudalgo.algoutils.student.annotation.StudentImplementationRequired;
+
+import h07.peano.NaturalNumber;
+import h07.peano.Successor;
+import h07.peano.Zero;
+
+import static org.tudalgo.algoutils.student.Student.crash;
+
+/**
+ * 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() {
+        // TODO: H2.2 - uncomment to test
+//        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() {
+        crash(); // TODO: H3.3 - remove if implemented
+    }
+
+    @StudentImplementationRequired
+    private static void filterFoldMapTests() {
+        crash(); // TODO: H4.6 - remove if implemented
+    }
+}

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

@@ -0,0 +1,65 @@
+package h07;
+
+import java.util.function.IntPredicate;
+
+import org.tudalgo.algoutils.student.annotation.DoNotTouch;
+import org.tudalgo.algoutils.student.annotation.StudentImplementationRequired;
+
+import static org.tudalgo.algoutils.student.Student.crash;
+
+/**
+ * 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) {
+//        return crash(); // TODO: H2.1 - remove if implemented
+//    }
+
+
+    // TODO: H2.2 - uncomment for testing
+    /**
+     * 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) {
+//        return crash(); // TODO: H4.4 - remove if implemented
+//    }
+}

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();
+}

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

@@ -0,0 +1,35 @@
+package h07.peano;
+
+
+import org.tudalgo.algoutils.student.annotation.StudentImplementationRequired;
+
+import static org.tudalgo.algoutils.student.Student.crash;
+
+/**
+ * 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) {
+//        return crash(); // TODO: H4.3 - remove if implemented
+//    }
+
+    /**
+     * 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) {
+//        return crash(); // TODO: H4.5 - remove if implemented
+//    }
+}

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() + ")";
+    }
+}

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";
+    }
+}

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);
+    }
+}