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package me.shaftesbury.utils.functional;

/**
 * An implementation of {@link me.shaftesbury.utils.functional.Func2} that is intended for use by the {@link me.shaftesbury.utils.functional.MException}
 * @param  the type of the first argument of the function
 * @param  the type of the second argument of the function
 * @param  the type of the return value of the function
 */
public abstract class BinaryFunction implements Func2
{
    /**
     * Create a curried unary function from this binary function
     * @return a function which takes an argument of type B and returns a function that accepts an argument of type A and returns
     * an object of type C
     */
    public Func> toFunc()
    {
        return toUnaryFunc(this);
    }

    /**
     * Helper function. The same as {@link #toFunc(Object)} above with the addition that the curried function is partially applied
     * by passing the argument b
     * @param b the argument to be passed to the curried function
     * @return a function that accepts an argument of type A and returns an object of type C
     */
    public Func toFunc(B b)
    {
        return toUnaryFunc(this).apply(b);
    }

    private static final Func> toUnaryFunc(final BinaryFunction f)
    {
        return new Func>()
        {
            @Override
            public Func apply(final B b) {
                return new Func() {
                    @Override
                    public C apply(final A a) {
                        return f.apply(a,b);
                    }
                };
            }
        };
    }

    /**
     * Given a {@link me.shaftesbury.utils.functional.Func2} and its two arguments, produce a function of no arguments that
     * can be evaluated at a later point.
     * @param f the two-parameter function
     * @param a the first parameter of f
     * @param b the second parameter of f
     * @param  the type of the first parameter of f
     * @param  the type of the second parameter of f
     * @param  the type of the return value of the delayed function
     * @return a function that takes no arguments and returns a value of type C
     */
    public static final Func0 delay(final Func2 f, final A a, final B b)
    {
        return new Func0() {
            @Override
            public C apply() {
                return f.apply(a,b);
            }
        };
    }
}