/jEdit/tags/jedit-4-1-pre5/bsh/BSHForStatement.java

/*****************************************************************************
 *                                                                           *
 *  This file is part of the BeanShell Java Scripting distribution.          *
 *  Documentation and updates may be found at http://www.beanshell.org/      *
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 *  Sun Public License Notice:                                               *
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 *  The contents of this file are subject to the Sun Public License Version  *
 *  1.0 (the "License"); you may not use this file except in compliance with *
 *  the License. A copy of the License is available at http://www.sun.com    * 
 *                                                                           *
 *  The Original Code is BeanShell. The Initial Developer of the Original    *
 *  Code is Pat Niemeyer. Portions created by Pat Niemeyer are Copyright     *
 *  (C) 2000.  All Rights Reserved.                                          *
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 *  GNU Public License Notice:                                               *
 *                                                                           *
 *  Alternatively, the contents of this file may be used under the terms of  *
 *  the GNU Lesser General Public License (the "LGPL"), in which case the    *
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 *                                                                           *
 *  Patrick Niemeyer (pat@pat.net)                                           *
 *  Author of Learning Java, O'Reilly & Associates                           *
 *  http://www.pat.net/~pat/                                                 *
 *                                                                           *
 *****************************************************************************/


package bsh;

/**
	Implementation of the for(;;) statement.
*/
class BSHForStatement extends SimpleNode implements ParserConstants
{
    public boolean hasForInit;
    public boolean hasExpression;
    public boolean hasForUpdate;

    private SimpleNode forInit;
    private SimpleNode expression;
    private SimpleNode forUpdate;
    private SimpleNode statement;

    private boolean parsed;

    BSHForStatement(int id) { super(id); }

    public Object eval(CallStack callstack , Interpreter interpreter)  
		throws EvalError
    {
        int i = 0;
        if(hasForInit)
            forInit = ((SimpleNode)jjtGetChild(i++));
        if(hasExpression)
            expression = ((SimpleNode)jjtGetChild(i++));
        if(hasForUpdate)
            forUpdate = ((SimpleNode)jjtGetChild(i++));
        if(i < jjtGetNumChildren()) // should normally be
            statement = ((SimpleNode)jjtGetChild(i));

		NameSpace enclosingNameSpace= callstack.top();
		BlockNameSpace forNameSpace = new BlockNameSpace( enclosingNameSpace );

		/*
			Note: some interesting things are going on here.

			1) We swap instead of push...  The primary mode of operation 
			acts like we are in the enclosing namespace...  (super must be 
			preserved, etc.)

			2) We do *not* call the body block eval with the namespace 
			override.  Instead we allow it to create a second subordinate 
			BlockNameSpace child of the forNameSpace.  Variable propogation 
			still works through the chain, but the block's child cleans the 
			state between iteration.  
			(which is correct Java behavior... see forscope4.bsh)
		*/

		// put forNameSpace it on the top of the stack
		// Note: it's important that there is only one exit point from this
		// method so that we can swap back the namespace.
		callstack.swap( forNameSpace );

		// If we wanted untyped variables in the for-init to be local, instead
		// of having side effects in the parent context of the for-loop we
		// could setInitMode() here to capture them and make them local.
		///forNameSpace.setInitMode(true); 

        // Do the for init
        if ( hasForInit ) 
            forInit.eval( callstack, interpreter );

		// If we had turned on init mode to capture untyped for-init vars 
		// and make them local to the for-loop scope we would turn it off here
		//forNameSpace.setInitMode(false); 

		Object returnControl = Primitive.VOID;
        while(true)
        {
            if ( hasExpression ) 
			{
				boolean cond = BSHIfStatement.evaluateCondition(
					expression, callstack, interpreter );

				if ( !cond ) 
					break;
			}

            boolean breakout = false; // switch eats a multi-level break here?
            if ( statement != null ) // not empty statement
            {
				// do *not* invoke special override for block... (see above)
                Object ret = statement.eval( callstack, interpreter );

                if (ret instanceof ReturnControl)
                {
                    switch(((ReturnControl)ret).kind)
                    {
                        case RETURN:
							returnControl = ret;
							breakout = true;
                            break;

                        case CONTINUE:
                            break;

                        case BREAK:
                            breakout = true;
                            break;
                    }
                }
            }

            if ( breakout )
                break;

            if ( hasForUpdate )
                forUpdate.eval( callstack, interpreter );
        }

		callstack.swap( enclosingNameSpace );  // put it back
        return returnControl;
    }

}