Bug 145022 Provide a utility method to help GUI enhance aggregate on.
DtE will provide a method hasAggregation(String expression) in org.eclipse.birt.core.data.ExpressionUtil, and the return value will be true when the expression is a valid JS expression and it has aggregation defined.
core/org.eclipse.birt.core/src/org/eclipse/birt/core/data/ExpressionParserUtility.java
* @param callNode
	 * @throws BirtException
	 */
	private void extractArguments( Node callNode, ScriptOrFnNode tree,
			List columnExprList ) throws BirtException
	{
		Node arg = callNode.getFirstChild( ).getNext( );
		while ( arg != null )
		{
			
			
			Node nextArg = arg.getNext( );
			processChild( callNode, arg, tree, columnExprList );
			arg = nextArg;
		}
	}
	/**
	 * compile the complex expression
	 * 
	 * @param complexNode
	 * @throws BirtException
	 */
	private void compileComplexExpr( Node complexNode, ScriptOrFnNode tree,
			List columnExprList ) throws BirtException
	{
		Node child = complexNode.getFirstChild( );
		while ( child != null )
		{
			if ( child.getType( ) == Token.FUNCTION )
			{