eval method
Evaluates against model (usually the context's main instance) in
context. The result is a bool, double, String, DateTime,
XPathNodeset or a value returned by a custom function.
Implementation
@override
Object eval(DataInstance? model, EvaluationContext context) {
final x = toNumeric(a.eval(model, context));
final y = toNumeric(b.eval(model, context));
return switch (op) {
CmpOp.lt => x < y,
CmpOp.gt => x > y,
CmpOp.lte => x <= y,
CmpOp.gte => x >= y,
};
}