/*
* evaluate the given expression.
*/
public Object evaluate(Expression e) {
if (e == null) {
return null;
}
if (debug) {
System.out.println("Evaluating expression: " + e);
}
if (e instanceof Literal) {
return ((Literal) e).getValue();
}
if (e instanceof Identifier) {
Identifier id = (Identifier) e;
if (map.containsKey(id.getName())) {
return map.get(id.getName());
} else {
// cache the data values for coherency of the values over
// the life of this expression executer.
Monitor m = (Monitor) id.getValue();
Object v = m.getValue();
map.put(id.getName(), v);
return v;
}
}
Expression l = e.getLeft();
Expression r = e.getRight();
Operator op = e.getOperator();
if (op == null) {
return evaluate(l);
} else {
Double lval = new Double(((Number) evaluate(l)).doubleValue());
Double rval = new Double(((Number) evaluate(r)).doubleValue());
double result = op.eval(lval.doubleValue(), rval.doubleValue());
if (debug) {
System.out.println("Performed Operation: " + lval + op + rval + " = " + result);
}
return new Double(result);
}
}
