java-cons

This small, one interface project is a try to reimplement the mechanics used in Rackets cons cells in Java.
git clone git://git.oshgnacknak.de/java-cons.git
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Empty.java (998B)

      1 import java.util.function.BiFunction;
      2 import java.util.function.Function;
      3 import java.util.function.Predicate;
      4 
      5 public class Empty<V> implements Cons<V> {
      6 
      7     @Override
      8     public V first() {
      9         throw new UnsupportedOperationException();
     10     }
     11 
     12     @Override
     13     public Cons<V> rest() {
     14         throw new UnsupportedOperationException();
     15     }
     16 
     17     @Override
     18     public <W> Cons<W> map(Function<V, W> mapper) {
     19         return new Empty<>();
     20     }
     21 
     22     @Override
     23     public Cons<V> filter(Predicate<V> predicate) {
     24         return new Empty<>();
     25     }
     26 
     27     @Override
     28     public <W> W foldl(BiFunction<V, W, W> f, W init) {
     29         return init;
     30     }
     31 
     32     @Override
     33     public <W> W foldr(BiFunction<V, W, W> f, W init) {
     34         return init;
     35     }
     36 
     37     @Override
     38     public boolean equals(Object obj) {
     39         return obj instanceof Empty;
     40     }
     41 
     42     @Override
     43     public boolean empty() {
     44         return true;
     45     }
     46 
     47     @Override
     48     public String toString() {
     49         return "empty";
     50     }
     51 }