typename usege problem ...

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  • 466
    #1

    typename usege problem ...

    Hi all,
    I have this member in a template class:

    bool opsInsert(int nId, T pObj){
    pairRet = insert(typename std::map<int,T> ::value_type(nI d, pObj)); }

    which does compile with gcc but not with cl.exe (Windows).
    If I remove the typename keyword, the code does not compile with gcc,
    but compiles witc cl.exe....

    The question: which is the standard way to call this function? Is there
    any workaround to make compile with both compilers?

    I know this is a compiler issue, but I hope you will help me ...

    thanx,
    stefan

    Tags: None
    • Rolf Magnus
      #2
      Re: typename usege problem ...

      466 wrote:
      Hi all,
      I have this member in a template class:
      >
      bool opsInsert(int nId, T pObj){
      pairRet = insert(typename std::map<int,T> ::value_type(nI d, pObj)); }
      >
      which does compile with gcc but not with cl.exe (Windows).
      If I remove the typename keyword, the code does not compile with gcc,
      but compiles witc cl.exe....
      >
      The question: which is the standard way to call this function?
      The standard requires the typename keyword in this place.
      Is there any workaround to make compile with both compilers?
      Maybe use a macro, like:

      #if compiler is vc++
      #define TYPENAME
      #else
      #define TYPENAME typename
      #endif

      bool opsInsert(int nId, T pObj){
      pairRet = insert(TYPENAME std::map<int,T> ::value_type(nI d, pObj)); }

      It's ugly, but works.

        Comment

        • 466
          #3
          Re: typename usege problem ...


          Rolf Magnus wrote:
          466 wrote:
          >
          Hi all,
          I have this member in a template class:

          bool opsInsert(int nId, T pObj){
          pairRet = insert(typename std::map<int,T> ::value_type(nI d, pObj)); }

          which does compile with gcc but not with cl.exe (Windows).
          If I remove the typename keyword, the code does not compile with gcc,
          but compiles witc cl.exe....

          The question: which is the standard way to call this function?
          >
          The standard requires the typename keyword in this place.
          >
          Is there any workaround to make compile with both compilers?
          >
          Maybe use a macro, like:
          >
          #if compiler is vc++
          #define TYPENAME
          #else
          #define TYPENAME typename
          #endif
          >
          bool opsInsert(int nId, T pObj){
          pairRet = insert(TYPENAME std::map<int,T> ::value_type(nI d, pObj)); }
          >
          It's ugly, but works.
          Sure, as a ultimate solution ... :(
          Thanx.

            Comment

            • Ron Natalie
              #4
              Re: typename usege problem ...

              466 wrote:
              Hi all,
              I have this member in a template class:
              >
              bool opsInsert(int nId, T pObj){
              pairRet = insert(typename std::map<int,T> ::value_type(nI d, pObj)); }
              >
              which does compile with gcc but not with cl.exe (Windows).
              If I remove the typename keyword, the code does not compile with gcc,
              but compiles witc cl.exe....
              >
              Get a version of the windows compiler that was published in the last
              five years.

                Comment

                • jim_taylor
                  #5
                  Re: typename usege problem ...

                  Maybe use a macro, like:
                  >
                  #if compiler is vc++
                  #define TYPENAME
                  #else
                  #define TYPENAME typename
                  #endif
                  >
                  You could use the macro
                  #define typename
                  as basically the older compilers don't know the typename keyword.
                  Be careful to make your #if specific to the current (and older)
                  versions of your compiler, as you don't want it to break when you do
                  upgrade...
                  Note also that the standard also allows typename as a synonym
                  (basically) for class in the template arguments,which also will not
                  work in yuour old compiler. i.e. you can write
                  template <typename MyType>

                    Comment

                    • Bo Persson
                      #6
                      Re: typename usege problem ...

                      jim_taylor wrote:
                      >Maybe use a macro, like:
                      >>
                      >#if compiler is vc++
                      >#define TYPENAME
                      >#else
                      >#define TYPENAME typename
                      >#endif
                      >>
                      >
                      You could use the macro
                      #define typename
                      as basically the older compilers don't know the typename keyword.
                      Except that in this case we recognize a certain compiler, that requires
                      typename in some places, doesn't care in other places, and flat out refuses
                      to recognize some cases where typename *is* required.

                      A very useful advice - use a compiler from this millennium - has alredy been
                      given by another poster.


                      Bo Persson


                        Comment

                        • Mark P
                          #7
                          Re: typename usege problem ...

                          466 wrote:
                          Hi all,
                          I have this member in a template class:
                          >
                          bool opsInsert(int nId, T pObj){
                          pairRet = insert(typename std::map<int,T> ::value_type(nI d, pObj)); }
                          >
                          which does compile with gcc but not with cl.exe (Windows).
                          If I remove the typename keyword, the code does not compile with gcc,
                          but compiles witc cl.exe....
                          >
                          The question: which is the standard way to call this function? Is there
                          any workaround to make compile with both compilers?
                          >
                          I know this is a compiler issue, but I hope you will help me ...
                          >
                          thanx,
                          stefan
                          >
                          As has been noted, the standard requires "typename". However you could
                          replace the expression by the actual type of value_type, namely
                          std::pair< const int, T>. That should not require "typename".

                            Comment

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