3 ms·

The examples are not wrong, you're just not understanding them. > It doesn't compile because foo is not constexpr. Well obviously. That's not the question her

The examples are not wrong, you're just not understanding them. > It doesn't compile because foo is not constexpr. Well obviously. That's not the question here. The question is, explain to me exactly what guarantee the declaring bar() as 'constexpr' achieved for anyone? It clearly didn't prevent its author from calling a non constexpr function, and it clearly didn't signal to its users that it is usable from a constexpr context either. The user had to go inspect each one of its callees manually to see if they could all be evaluated at compile time in reality, which is exactly what you just did with foo(). Which is pretty damn hard (as in, Turing-undecidably-hard) when things are templates and you have ADL on top of that. And which the presence of constexpr on bar() didn't help you one bit with. The declaration of bar() told you exactly nothing by having constexpr in it. It made no difference whatsoever for itself, nor for main(). It just added clutter.

rowanG077 5y ago
The code doesn't compile, so it did in fact stop the author from calling a non-constexpr function from a constexpr function. You can't meaningfully semantically talk about code that doesn't compile.
- dataflow 5y ago
  > You can't meaningfully semantically talk about code that doesn't compile. You can point out that it failed to compile, and that can be a benefit when compiling would've been detrimental. Just like you yourself literally just did when you said "The code doesn't compile [...]". > it did in fact stop the author from calling a non-constexpr function from a constexpr function. The constexpr in front of bar() is not what prevented compilation. You don't believe me? Just take it out and see. The code would've failed to compile the exact same way without constexpr in front of bar(). Try it before disagreeing with me. You're saying putting constexpr in front of bar() has a benefit. I'm saying: tell me what it was. Making that constexpr be always in front of bar() implicitly would've resulted in exactly the same outcome in every situation where the code compiles and also where it fails to compile (like above). Nothing would've been any different. I don't get why this is so difficult but I'm not going to keep repeating myself. Everything I can possibly imagine explaining is in my comments up to this point so just re-read them, I have no other way I can phrase these. Everyone else has understood what I'm saying and I'm at a loss how else to explain it differently. I promise you it's not wrong, we're just failing to communicate.

rowanG077 5y ago

The code doesn't compile, so it did in fact stop the author from calling a non-constexpr function from a constexpr function. You can't meaningfully semantically talk about code that doesn't compile.

dataflow 5y ago
> You can't meaningfully semantically talk about code that doesn't compile. You can point out that it failed to compile, and that can be a benefit when compiling would've been detrimental. Just like you yourself literally just did when you said "The code doesn't compile [...]". > it did in fact stop the author from calling a non-constexpr function from a constexpr function. The constexpr in front of bar() is not what prevented compilation. You don't believe me? Just take it out and see. The code would've failed to compile the exact same way without constexpr in front of bar(). Try it before disagreeing with me. You're saying putting constexpr in front of bar() has a benefit. I'm saying: tell me what it was. Making that constexpr be always in front of bar() implicitly would've resulted in exactly the same outcome in every situation where the code compiles and also where it fails to compile (like above). Nothing would've been any different. I don't get why this is so difficult but I'm not going to keep repeating myself. Everything I can possibly imagine explaining is in my comments up to this point so just re-read them, I have no other way I can phrase these. Everyone else has understood what I'm saying and I'm at a loss how else to explain it differently. I promise you it's not wrong, we're just failing to communicate.