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
ResourceConstants.INVALID_EXPRESSION );
				}
				Node exprNode = tree.getFirstChild( );
				Node child = exprNode.getFirstChild( );
				assert ( child != null );
				processChild( exprNode, child, tree, columnExprList );
			}
		}
		else
		{
			compileComplexExpr( tree, tree, columnExprList );
		}
	}
	/**
	 * parse the expression into a script tree
	 * 
	 * @param expression
	 * @param cx
	 * @return
	 */
	private ScriptOrFnNode parse( String expression, Context cx )
	{
		CompilerEnvirons compilerEnv = new CompilerEnvirons( );
		Parser p = new Parser( compilerEnv, cx.getErrorReporter( ) );
		return p.parse( expression, null, 0 );
	}
	/**
	 * process child node
	 * 
	 * @param parent