001package Torello.Java.Function;
002
003import java.util.function.Function;
004
005/**
006 * Function-Pointer
007 * <SPAN CLASS=TJF>Input:</SPAN> {@code int, int, int}
008 * <SPAN CLASS=TJF>Output:</SPAN> {@code R}.
009 * 
010 * <BR /><BR />
011 * Primitive's Extension to Java's {@code java.util.function.*} package.
012 * <BR /><BR />This {@code FunctionalInterface} has an {@code apply(...)} method which accepts
013 * three primitives: three {@code int}-primitives.
014 */
015@FunctionalInterface
016public interface TriIntFunc<R>
017{
018    /**
019     * Applies a user-provided function to input aruments, returning a result of type {@code R}
020     * @param i1 The first integer-parameter.
021     * @param i2 The second integer-parameter.
022     * @param i3 The third integer-parameter.
023     * @return The result of the function.  Return result is of type {@code 'R'}
024     */
025    public R apply(int i1, int i2, int i3);
026
027    /**
028     * Returns a composed function that first applies {@code 'this'} function to its input, and
029     * then applies the {@code 'after'} function to the result. If evaluation of either function
030     * throws an exception, it is relayed to the caller of the composed function.
031     * 
032     * @param <V> The output-type of the {@code 'after'} function, and also of the (returned)
033     * {@code 'composed'} function.
034     * 
035     * @param after The function to apply, after this function is applied.
036     * @throws NullPointerException This throws if null is passed to {@code 'after'}.
037     */
038    public default <V> TriIntFunc<V> andThen(Function<R, V> after)
039    {
040        if (after == null) throw new NullPointerException
041            ("null has been passed to parameter 'after'");
042
043        return (int i1, int i2, int i3) -> after.apply(this.apply(i1, i2, i3));
044    }
045}