Re: [boost] safe bool operator

Subject: Re: [boost] safe bool operator
From: Jeffrey Hellrung (jhellrung_at_[hidden])
Date: 2010-03-04 04:03:56

Domagoj Saric wrote:
> "Scott McMurray" <me22.ca+boost_at_[hidden]> wrote in message 
> news:fa28b9251003011306k77a61047l4e0236ebbd6d8dc3_at_mail.gmail.com...
>> Is there a reason it can't just always look at operator!?
>>
>> I've been using a macro like this, since I don't need the workarounds:
>>
>> #define OPERATOR_SAFE_BOOL(for_type) \
>>    typedef bool (for_type::*unspecified_bool_type)() const; \
>>    operator unspecified_bool_type() const { \
>>        return !*this ? 0 : &for_type::operator!; \
>>    }
> 
> This forces classes to have operator! and it still suffers from efficiency 
> issues outlined in the first post...

I don't think the requirement for operator! is so bad (should certainly 
satisfy the majority of use cases, right?), and perhaps efficiency can 
be addressed by defining the "unspecified_bool_type" conversion in debug 
builds and a straight bool conversion in release builds for "problem" 
compilers...?  Or perhaps some other preprocessor macro can direct 
whether to go with the type-safe version (default) or the efficient 
version (which may in fact be the same for some compilers)...?

- Jeff