Question

In my compiler project, I have an enumeration that goes like

enum Result {
  No,
  Maybe,
  Yes
};

I have put No explicitly at the first position, so that i can rely on the boolean evaluation to false. If my compiler is not sure about something, and has to wait for facts until runtime, its analysis functions will return Maybe. Used like

if(!typesEqual(t1, t2)) {
  diagnose(types_unequal) << t1 << t2;
}

I wonder whether you or your company considers it bad style not to compare to No explicitly

if(typesEqual(t1, t2) == No) { /* ... */ }

Comparing explicitly seems wordy to me, but relying on the implicit boolean conversion somehow makes me feel guilty. Have you had that feeling before, and how have you dealt with it?

Answer 1

I’d feel guilty about it as well, because from reading the code above what would you expect the boolean typesEqual() expression to return for a Maybe? Would it return true? Maybe! Would it return false? Maybe! We don’t know – that’s the entire point of the enum. That’s why it makes sense to explicitly compare to No, even though it’s more verbose.