Re: [boost] Boost Optional

Subject: Re: [boost] Boost Optional
From: Stewart, Robert (Robert.Stewart_at_[hidden])
Date: 2012-03-29 07:21:15

Rafael Justo wrote:
>
[I trimmed your example:]
> boost::optional<Test> get();
>
> int main()
> {
>   if (get() == true) {
>     // OK
>   } else if (get() == false) {
>     // ERROR
>   }
> }
>
> But there's no "operator==" with bool in optional.hpp,
> so the above code don't compile (i have checked version
> 1.49).

I agree with the other posters that such verbosity is unnecessary.

> Is it possible to add the patch described bellow in
> optional.hpp to solve this problem?
>
> +    bool operator== (const bool condition)
> +      {
> +        return ((*this && condition) || (!*this &&
> !condition));
> +      }
> +

That would make optionals equality comparable with anything that can be converted to bool, so the following would be valid:

   if (get() == 3) // int is convertible to bool
   {
      // OK?
   }

Comparing boost::optional<Test> with int or anything else convertible to bool is inappropriate and was the reason to introduce the Safe Bool Idiom in the first place.

_____
Rob Stewart                           robert.stewart_at_[hidden]
Software Engineer                     using std::disclaimer;
Dev Tools & Components
Susquehanna International Group, LLP  http://www.sig.com

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