Re: [boost] [mpl] Using apply with gcc error

Subject: Re: [boost] [mpl] Using apply with gcc error
From: Larry Evans (cppljevans_at_[hidden])
Date: 2011-02-03 18:08:17

On 02/03/11 17:02, Steven Watanabe wrote:
> AMDG
> 
> On 2/3/2011 2:42 PM, Edward Diener wrote:
>> Compiling this code with gcc:
>>
>> #include <boost/config.hpp>
>> #include <boost/mpl/apply.hpp>
>>
>> template
>> <
>> class MF,
>> class T
>>  >
>> struct myMF :
>> boost::mpl::apply<MF,T>
>> {
>> BOOST_STATIC_CONSTANT(bool,value=type::value);
>> };
>>
>> int main()
>> {
>> return 0;
>> }
>>
>> Gives:
>>
>> "gcc.compile.c++
>> ..\..\..\bin.v2\libs\tti\test\TestMFHasTypeMFC.test\gcc-mingw-4.5.2\debug\TestMFHasTypeMFC.o
>>
>>
>> TestMFHasTypeMFC.cpp:18:5: error: 'type' has not been declared
>>
> 
> gcc is correct.  Members of a dependent base class are
> not visible in the derived class.  (This is necessary
> to allow the template to be parsed before the template
> arguments are known.).
> 
> Add
> using typename boost::mpl::apply<MF,T>::type;
> 
> In Christ,
> Steven Watanabe
> _______________________________________________
That using works with clang++; however, my gcc (gcc4.5.1)
still doesn't like it:

make using
cat myMF.cpp
//Copied from post with headers:
/*
From: Edward Diener <eldiener_at_[hidden]>
Newsgroups: gmane.comp.lib.boost.devel
Subject: [mpl] Using apply with gcc error
Date: Thu, 03 Feb 2011 17:42:44 -0500
Lines: 47
 */
#include <boost/config.hpp>
#include <boost/mpl/apply.hpp>

   template
     <
     class MF,
     class T
     >
   struct myMF :
     boost::mpl::apply<MF,T>
     {
     using typename boost::mpl::apply<MF,T>::type;
     BOOST_STATIC_CONSTANT(bool,value=type::value);
     };

   int main()
     {
     return 0;
     }
/home/evansl/download/llvm/svn/build/Debug+Asserts/bin/clang++ -c
-std=c++0x -U__GXX_EXPERIMENTAL_CXX0X__ -c myMF.cpp
/home/evansl/download/gcc/4.5.1-release/install/bin/g++ -c -Wall
-ftemplate-depth-300 -O0 -std=gnu++0x -c myMF.cpp
myMF.cpp:21:6: error: 'type' is not a class, namespace, or enumeration
make: [using] Error 1 (ignored)

Compilation finished at Thu Feb  3 17:04:44