Re: template #if preprocessor

From:
 James Kanze <james.kanze@gmail.com>
Newsgroups:
comp.lang.c++
Date:
Thu, 09 Aug 2007 11:05:33 -0000
Message-ID:
<1186657533.753998.163900@l70g2000hse.googlegroups.com>
On Aug 8, 2:50 pm, kRyszard <kry...@gmail.com> wrote:

how to make the following code work:

template<class TYPE>
void f2(char *buffer, TYPE *outer) {
     // do something ...
     // ...
#if (TYPE == int)
        *outer = atoi(buffer);
#endif
#if (TYPE == double)
        *outer = atof(buffer);
#endif
#if (TYPE == char)
        strcpy(outer, buffer);
#endif
     // release memory here
     // ...


None of my business, of course, but what memory are you
releasing?

        return;
}

it is not working but maybe you know how to modify it to make it
work...


In this precise case, of course, the obvious solution is:

    template< typename T >
    void
    f2( char const* buffer, T* dest )
    {
        std::istrstream s( buffer, strlen( buffer ) ) ;
        s >> *dest ;
        // Error checking here...
    }

If this is just an example of a more general problem, of
course...

    template< typename T >
    struct Cvt
    {
        static T convert( char const* buffer ) ;
    } ;

    template< typename T >
    void
    f2( char const* buffer, T* dest )
    {
        // ...
        *dest = Cvt< T >::convert( buffer ) ;
        // ...
    }

    template<>
    struct Cvt< int >
    {
        static int convert( char const* buffer )
        {
            return atoi( buffer ) ;
        }
    } ;

    template<>
    struct Cvt< double >
    {
        static int convert( char const* buffer )
        {
            return atof( buffer ) ;
        }
    } ;

    // ...

--
James Kanze (GABI Software) email:james.kanze@gmail.com
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