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package lv.enes.mc.eris_alchemy.utils;
import jakarta.annotation.Nonnull;
import java.util.Objects;
import java.util.Optional;
import java.util.function.Supplier;
import java.util.stream.Stream;
public sealed abstract class ConsList<E> {
public static <E> ConsList<E> cons(E car, ConsList<E> cdr) {
return new Cons<>(car, cdr);
}
public static <E> ConsList<E> nil() {
return Nil.of();
}
@Nonnull
public abstract Optional<E> car();
@Nonnull
public abstract ConsList<E> cdr();
public boolean contains(E elem) {
return stream().anyMatch(x -> Objects.equals(x, elem));
}
public Stream<E> stream() {
var car = car();
if (car.isEmpty()) {
return Stream.empty();
}
return Stream.<Supplier<Stream<E>>>of(
() -> Stream.of(car.get()),
() -> cdr().stream()
)
.flatMap(Supplier::get);
}
@Override
public String toString() {
if (car().isEmpty()) {
return "[]";
}
var sb = new StringBuilder("[");
sb.append(car().get());
stream().skip(1)
.forEach(x -> {
sb.append(" -> ");
sb.append(x);
});
sb.append("]");
return sb.toString();
}
private static final class Cons<E> extends ConsList<E> {
private final E car;
private final ConsList<E> cdr;
public Cons(E car, ConsList<E> cdr) {
this.car = car;
this.cdr = cdr;
}
@Nonnull
@Override
public Optional<E> car() {
return Optional.of(car);
}
@Nonnull
@Override
public ConsList<E> cdr() {
return cdr;
}
}
private static final class Nil<E> extends ConsList<E> {
private static final Nil<?> INSTANCE = new Nil<>();
@SuppressWarnings("unchecked")
public static <E> Nil<E> of() {
return (Nil<E>)INSTANCE;
}
private Nil(){}
@Nonnull
@Override
public Optional<E> car() {
return Optional.empty();
}
@Nonnull
@Override
public ConsList<E> cdr() {
return Nil.of();
}
}
}
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