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Hello,

the code here doesn't compile:

#include <boost/mpl/string.hpp> #include <iostream>

namespace mpl = boost::mpl;

typedef mpl::string<'h','e','l','l','o',' ','w','o','r','l','d'>::type my_hello;

int main() {     std::cout << mpl::c_str<my_hello>::value << '\n';     std::cout << BOOST_MPL_LIMIT_STRING_SIZE << '\n'; }

As usual, the example from docs works. The error is: <snip>

I'm surprised multi-character character constants are being used at all in Boost, they are not supposed to be portable:

http://stackoverflow.com/questions/6944730/multiple-characters-in-a-characte...

Boost has never shied away from non-portable constructs. However, it *does* wrap non-portable constructs in config macros to ensure a consistent cross-platform experience, which is what mpl::string does with multichar literals.

Does the wrapping include handling 'qwer' on platforms where int is not 4 bytes? It may, I don't have a way to test it.

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If you only want to use single character constants, you could place the following #define before any includes:

#define BOOST_MPL_LIMIT_STRING_SIZE (32*4)

That would allow up to 32, provided your compiler supports it (yet another portability issue).>>

That would increase the compile time and decrease readability for no benefit, IMO.

Opinions may differ on the readability of:     typedef mpl::string<'hell','o wo','rld'> ...... vs:     typedef mpl::string<'h','e','l','l','o',' ','w','o','r','l','d'>..... But increasing compile time would be bad. That's why I'm asking if it would be possible for there to be an mpl::string<> that takes BOOST_MPL_LIMIT_STRING_SIZE 'char's? [It looks like 'x' started being a char in C++11, so it may be complicated supporting prior versions]

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Since in C++, the type of 'x' is char, it should be possible to create another overload of mpl::string<> that takes BOOST_MPL_LIMIT_STRING_SIZE 'char's, which would work the way most people would expect..

How do you think most people expect it to work?

My opinion is that most programmers would expect BOOST_MPL_LIMIT_STRING_SIZE single character constants to work. I know that multi-character constants are not always portable, so I try not to use them, even if a particular instance may be portable.

-- Eric Niebler Boost.org http://www.boost.org

Dan Searles