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Naive implementation of Either in JAva
package bad.robot;
import fj.F;
import java.util.function.Function;
import java.util.stream.Stream;
public interface Either<A, B> {
static <A, B> Either<A, B> left(final A a) {
return new Left<>(a);
}
static <A, B> Either<A, B> right(final B b) {
return new Right<>(b);
}
static <T, R> Function<T, Either<Pair<T, Throwable>, R>> asEithers(Function<T, R> function) {
return (T a) -> {
try {
return Either.<Pair<T, Throwable>, R>right(function.apply(a));
} catch (Throwable e) {
return left(Pair.pair(a, e));
}
};
}
Boolean isLeft();
Boolean isRight();
Stream<A> left();
Stream<B> right();
class Left<A, B> implements Either<A, B> {
private final A value;
public Left(A value) {
this.value = value;
}
@Override
public Boolean isLeft() {
return true;
}
@Override
public Boolean isRight() {
return false;
}
@Override
public Stream<A> left() {
return Stream.of(value);
}
@Override
public Stream<B> right() {
return Stream.empty();
}
}
class Right<A, B> implements Either<A, B> {
private final B value;
public Right(B value) {
this.value = value;
}
@Override
public Boolean isLeft() {
return false;
}
@Override
public Boolean isRight() {
return true;
}
@Override
public Stream<B> right() {
return Stream.of(value);
}
@Override
public Stream<A> left() {
return Stream.empty();
}
}
}
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