Re: [Boost-users] mpl::c_str<mpl::string<>> compile error

Subject: Re: [Boost-users] mpl::c_str<mpl::string<>> compile error
From: Eric Niebler (eniebler_at_[hidden])
Date: 2013-05-07 12:33:30

On 13-05-06 10:44 PM, Olaf Peter wrote:
>> Have you tried:
>>
>>    typedef mpl::string<'hell','o wo','rld'>::type
>>    my_hello;
>>
>> ? BOOST_MPL_LIMIT_STRING_SIZE is a count of "characters" in the
>> mpl::string, which is 4X the number of template parameters, since
>> mpl::string uses multi-character literals to pack 4 characters into an
>> int.
> 
> Thanks, Eric. This is from the examples and works. But there rises the
> question how to use slightly longer mpl strings. 

I don't understand the problem you're having. If you want a longer
string, you just add more characters:

typedef
   mpl::string<'hell','o wo','rld ','abcd','efgh'>::type
my_hello;

If you want to append piecemeal, use mpl::push_back, which will do the
right thing.

> Further more, using
> this emits a compiler warning about multichar literal (or similar) on
> gcc. Generally disabling this warning may prevent detection of issues on
> other places.

Because you're using multichar literals in so many other places? ;-)

> A similar compile problem I have with
> 
> typedef mpl::char<'A'>::type my_A;
> 
> int main()
> {
>     std::cout << mpl::c_str<my_A>::value << '\n';
> }
> 
> but I haven't a compiler at the hand here.

mpl::c_str only works on mpl::strings.

-- 
Eric Niebler
Boost.org