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Functional patterns for Java

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package com.jnape.palatable.lambda.functions.builtin.fn2;

import com.jnape.palatable.lambda.functions.Fn1;
import com.jnape.palatable.lambda.functions.Fn2;

import java.util.Optional;
import java.util.function.BiFunction;

import static com.jnape.palatable.lambda.functions.builtin.fn1.Reverse.reverse;
import static com.jnape.palatable.lambda.functions.builtin.fn2.ReduceLeft.reduceLeft;

/**
 * Given an Iterable of As and a {@link BiFunction}<A, A, A>, iteratively
 * accumulate over the Iterable, returning an Optional<A>  (if the Iterable
 * is empty, the result is Optional.empty(); otherwise, the result is wrapped in
 * Optional.of(). For this reason, null accumulation results are considered erroneous and will
 * throw.
 * 
 * This function is isomorphic to a right fold over the Iterable where the tail element is the starting
 * accumulation value and the result is lifted into an Optional.
 *
 * @param  The input Iterable element type, as well as the accumulation type
 * @see ReduceLeft
 * @see com.jnape.palatable.lambda.functions.builtin.fn3.FoldRight
 */
public final class ReduceRight implements Fn2, Iterable, Optional> {

    private ReduceRight() {
    }

    @Override
    public final Optional apply(BiFunction fn, Iterable as) {
        return reduceLeft((b, a) -> fn.apply(a, b), reverse(as));
    }

    public static  ReduceRight reduceRight() {
        return new ReduceRight<>();
    }

    public static  Fn1, Optional> reduceRight(BiFunction fn) {
        return ReduceRight.reduceRight().apply(fn);
    }

    public static  Optional reduceRight(BiFunction fn, Iterable as) {
        return ReduceRight.reduceRight(fn).apply(as);
    }
}