/**
* Parses the expression. If there are errors in the expression, they are added to the <code>
* errorList</code> member. Errors can be obtained through <code>getErrorInfo()</code>.
*
* @param expression_in The input expression string
* @return the top node of the expression tree if the parse was successful, <code>null</code>
* otherwise
*/
public Node parseExpression(String expression_in) {
Reader reader = new StringReader(expression_in);
try {
// try parsing
errorList.removeAllElements();
topNode = parser.parseStream(reader, this);
// if there is an error in the list, the parse failed
// so set topNode to null
if (hasError()) topNode = null;
} catch (Throwable e) {
// an exception was thrown, so there is no parse tree
topNode = null;
// check the type of error
if (e instanceof ParseException) {
// the ParseException object contains additional error
// information
errorList.addElement(((ParseException) e).getMessage());
// getErrorInfo());
} else {
// if the exception was not a ParseException, it was most
// likely a syntax error
if (debug) {
System.out.println(e.getMessage());
e.printStackTrace();
}
errorList.addElement("Syntax error");
}
}
// If traversing is enabled, print a dump of the tree to
// standard output
if (traverse && !hasError()) {
ParserVisitor v = new ParserDumpVisitor();
try {
topNode.jjtAccept(v, null);
} catch (ParseException e) {
errorList.addElement(e.getMessage());
}
}
return topNode;
}
/**
* 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();
}
public Object eval(Node node) throws ParseException {
MatrixValueI val = (MatrixValueI) node.jjtAccept(this, null);
return val.copy();
}
/**
* Evaluates a given node, in the current context.
*
* @param node The node to evaluate
* @return result of the evaluation
*/
public Object eval(Node node) throws ParseException {
node.jjtAccept(this, null);
return stack.pop();
}