Re: [boost] [IdentityType] Const omission undocumented.

3 Dec 2013


      On Tue, 03 Dec 2013 11:23:46 -0800, Krzysztof Czainski  
<1czajnik@gmail.com> wrote:
...
2013/12/3 Lorenzo Caminiti 
...
On Sat, Nov 16, 2013 at 11:18 AM, Mathias Gaunard
 wrote:
...
On 16/11/2013 01:02, Mostafa wrote:
...
#include 
#include <utility>
int main()
{
   BOOST_IDENTITY_TYPE(( std::pair const )) x;
   // This compiles, so the const qualification in the
   // above macro parameter is ignored.
   x = std::make_pair(0,1);
return 0;
}
The omission of const qualification in BOOST_IDENTITY_TYPE types is
undocumented. This omission maybe deduced from the documented
implementation, but, as noted, that is not part of the library api
and
...
is subject to change. I therefore propose that this behaviour be
documented as part of the library's public api.
That looks like a bug.
Is there a way to extract the cv-qualifier from a function parameter
type at compile-time?
some_mata_function::type // evaluates to `int const`
not just `int`
Right now I do the following which looses the cv-qualifier (I also
tried to program my own meta-functions but I wan't able to retain the
cv-qualifier).
boost::function_traits::arg1_type // evaluates to
`int` and not to `int conat` :(
how about (not tested):
boost::remove_reference< boost::function_traits::arg1_type >::type
Pointers should be used instead. References will lead to bugs because of  
reference collapsing when add_reference is used. For example:

BOOST_IDENTITY_TYPE(( std::pair & )) x;

will be incorrectly deduced as std::pair