Re: [boost] [Convert] std::isspace requires unsigned #28

Subject: Re: [boost] [Convert] std::isspace requires unsigned #28
From: Gavin Lambert (gavinl_at_[hidden])
Date: 2017-03-21 01:49:09

On 21/03/2017 13:46, Vladimir Batov via Boost wrote:
> Thanks, Gavin, indeed I should have a dig in char_traits before
> re-inventing the wheel. Thanks.

There's also std::ctype<char/wchar_t>::is(), although the call syntax 
for that seems a bit more cumbersome.  Also at least according to 
cppreference.com it hasn't been extended for the new 16-bit and 32-bit 
C++11 char types.  I don't know if that means anything.

> What about iswspace()? Does it have the same problem as std::isspace(),
> i.e. needs an explicit cast? Seems unlikely...

I think it's probably good practice to use char_traits<>::to_int_type() 
for that too, since the parameter type is wint_t rather than wchar_t, 
and that's the "right" way to do that conversion.

As Peter said in practice it probably wouldn't cause any bugs without 
that since it would be weird for wchar_t to be signed, but as both the 
sign and size of the type is implementation-defined it's not actually 
illegal for that to be the case.  (And you're even less likely to notice 
on platforms where wchar_t is 32-bit or larger, but again that's 
implementation-defined.)