/**
* Visit a function node. The values of the child nodes are first pushed onto the stack. Then the
* function class associated with the node is used to evaluate the function.
*
* <p>If a function implements SpecialEvaluationI then the evaluate method of PFMC is called.
*/
public Object visit(ASTFunNode node, Object data) throws ParseException {
if (node == null) return null;
PostfixMathCommandI pfmc = node.getPFMC();
// check if the function class is set
if (pfmc == null)
throw new ParseException("No function class associated with " + node.getName());
// Some operators (=) need a special method for evaluation
// as the pfmc.run method does not have enough information
// in such cases we call the evaluate method which passes
// all available info. Note evaluating the children is
// the responsibility of the evaluate method.
if (pfmc instanceof SpecialEvaluationI) {
return ((SpecialEvaluationI) pfmc).evaluate(node, data, this, stack, this.symTab);
}
if (pfmc instanceof CallbackEvaluationI) {
Object val = ((CallbackEvaluationI) pfmc).evaluate(node, this);
stack.push(val);
return val;
}
if (debug == true) {
System.out.println("Stack size before childrenAccept: " + stack.size());
}
// evaluate all children (each leaves their result on the stack)
data = node.childrenAccept(this, data);
if (debug == true) {
System.out.println("Stack size after childrenAccept: " + stack.size());
}
if (pfmc.getNumberOfParameters() == -1) {
// need to tell the class how many parameters it can take off
// the stack because it accepts a variable number of params
pfmc.setCurNumberOfParameters(node.jjtGetNumChildren());
}
// try to run the function
pfmc.run(stack);
if (debug == true) {
System.out.println("Stack size after run: " + stack.size());
}
return data;
}
/**
* Returns the value of the expression as an object. The expression tree is specified with its top
* node. The algorithm uses a stack for evaluation.
*
* <p>The symTab parameter can be null, if no variables are expected in the expression. If a
* variable is found, an error is added to the error list.
*
* <p>An exception is thrown, if an error occurs during evaluation.
*
* @return The value of the expression as an object.
* @throws ParseException if there is a problem with the evaluation.
*/
public Object getValue(Node topNode, SymbolTable symTab_in) throws ParseException {
// check if arguments are ok
if (topNode == null) {
throw new ParseException("topNode parameter is null");
}
// set member vars
// errorList = errorList_in;
symTab = symTab_in;
// System.out.println("Evaluating expression " + topNode.toLongString() + " with symTab: " +
// symTab);
// errorFlag = false;
stack.removeAllElements();
// rjm addition ensure stack is correct before beginning.
// njf changed from clear() to removeAllElements for 1.1 compatibility
// evaluate by letting the top node accept the visitor
topNode.jjtAccept(this, null);
/*
} catch (ParseException e) {
this.addToErrorList("Error: "+e.getMessage());
return null;
}
if(errorFlag) return null;
*/
// something is wrong if not exactly one item remains on the stack
// or if the error flag has been set
if (stack.size() != 1) {
throw new ParseException("Stack corrupted");
}
// return the value of the expression
return stack.pop();
}
