/**
  * Copyright (c): Uwe Schmidt, FH Wedel
  *
  * You may study, modify and distribute this source code
  * FOR NON-COMMERCIAL PURPOSES ONLY.
  * This copyright message has to remain unchanged.
  *
  * Note that this document is provided 'as is',
  * WITHOUT WARRANTY of any kind either expressed or implied.
  */

package ds.util;

abstract public
    class Function2<X,Y,Z> {

    // apply a binary function
    abstract public Z apply(X x, Y y);

    public Function2<Y,X,Z> flip() {
	return
	    new Flip<Y,X,Z>(this);
    }

    private static class Flip<X,Y,Z> extends Function2<X,Y,Z> {
	private final Function2<Y,X,Z> f;

	public Flip(Function2<Y,X,Z> f) {
	    this.f = f;
	}

	public Z apply(X x, Y y) {
	    return
		f.apply(y, x);
	}
    }
}