/*****************************************************************************

 JEP 2.4.1, Extensions 1.1.1
      April 30 2007
      (c) Copyright 2007, Nathan Funk and Richard Morris
      See LICENSE-*.txt for license information.

 *****************************************************************************/

package weasel.jep.function;


import java.util.Stack;

import weasel.jep.ParseException;


/**
 * All function classes must implement this interface to ensure that the run()
 * method is implemented.
 */
public interface PostfixMathCommandI {
	/**
	 * Run the function on the stack. Pops the arguments from the stack, and
	 * pushes the result on the top of the stack.
	 */
	public void run(Stack aStack) throws ParseException;

	/**
	 * Returns the number of required parameters, or -1 if any number of
	 * parameters is allowed.
	 */
	public int getNumberOfParameters();

	/**
	 * Sets the number of current number of parameters used in the next call of
	 * run(). This method is only called when the reqNumberOfParameters is -1.
	 */
	public void setCurNumberOfParameters(int n);

	/**
	 * Checks the number of parameters of the function. This method is called
	 * during the parsing of the equation to check syntax. Functions which set
	 * numberOfParameter=-1 should overwrite this method.
	 * 
	 * @param n number of parameters function will be called with.
	 * @return False if an illegal number of parameters is supplied, true
	 *         otherwise.
	 */
	public boolean checkNumberOfParameters(int n);

}
