org/luaj/vm2/lib/VarArgFunction.java

/*******************************************************************************
* Copyright (c) 2009 Luaj.org. All rights reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
* 
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
******************************************************************************/
package org.luaj.vm2.lib;

import org.luaj.vm2.LuaValue;
import org.luaj.vm2.Varargs;

/** Abstract base class for Java function implementations that takes varaiable arguments and 
 * returns multiple return values. 
 * <p>
 * Subclasses need only implement {@link LuaValue#invoke(Varargs)} to complete this class, 
 * simplifying development.  
 * All other uses of {@link #call(LuaValue)}, {@link #invoke()},etc, 
 * are routed through this method by this class,
 * converting arguments to {@linnk Varargs} and  
 * dropping or extending return values with {@code nil} values as required.
 * <p>
 * If between one and three arguments are required, and only one return value is returned,   
 * {@link ZeroArgFunction}, {@link OneArgFunction}, {@link TwoArgFunction}, or {@link ThreeArgFunction}.
 * <p>
 * See {@link LibFunction} for more information on implementation libraries and library functions.
 * @see #invoke(Varargs)
 * @see LibFunction
 * @see ZeroArgFunction
 * @see OneArgFunction
 * @see TwoArgFunction
 * @see ThreeArgFunction
 */
abstract public class VarArgFunction extends LibFunction {

	public VarArgFunction() {
	}
	
	public LuaValue call() {
		return invoke(NONE).arg1();
	}

	public LuaValue call(LuaValue arg) {
		return invoke(arg).arg1();
	}

	public LuaValue call(LuaValue arg1, LuaValue arg2) {
		return invoke(varargsOf(arg1,arg2)).arg1();
	}

	public LuaValue call(LuaValue arg1, LuaValue arg2, LuaValue arg3) {
		return invoke(varargsOf(arg1,arg2,arg3)).arg1();
	}

	/** 
	 * Subclass responsibility. 
	 * May not have expected behavior for tail calls. 
	 * Should not be used if:
	 * - function has a possibility of returning a TailcallVarargs
	 * @param args the arguments to the function call.
	 */
	public Varargs invoke(Varargs args) {
		return onInvoke(args).eval();
	}
	
	public Varargs onInvoke(Varargs args) {
		return invoke(args);
	}
}