Identifying primitive types in templates

Question

I am looking for a way to identify primitives types in a template class definition.

I mean, having this class :

template
class A{
void         


        

Answer 1

The following example (first posted in comp.lang.c++.moderated) illustrates using partial specialisation to print things differently depending on whether or not they are built-in types.

// some template stuff
//--------------------
#include 
#include 
#include 

using namespace std;

// test for numeric types
//-------------------------
template  struct IsNum {
    enum { Yes = 0, No = 1 };
};


template <> struct IsNum  { 
    enum { Yes = 1, No = 0 };
};


template <> struct IsNum  {
    enum { Yes = 1, No = 0 };
};

// add more IsNum types as required

// template with specialisation for collections and numeric types
//---------------------------------------------------------------
template  struct Printer {
    void Print( const T & t ) {
        typename T::const_iterator it = t.begin();
        while( it != t.end() ) {
            cout << *it << " ";
            ++it;
        }
        cout << endl;
    }
};

template  struct Printer  {
    void Print( const T & t ) {
        cout << t << endl;
    }
};

// print function instantiates printer depoending on whether or
// not we are trying to print numeric type
//-------------------------------------------------------------
template  void MyPrint( const T & t ) {
    Printer ::Yes> p;
    p.Print( t );
}

// some test types
//----------------
typedef std::vector  Vec;
typedef std::list  List;

// test it all
//------------
int main() {

    Vec x;
    x.push_back( 1 );
    x.push_back( 2 );
    MyPrint( x );        // prints 1 2

    List y;
    y.push_back( 3 );
    y.push_back( 4 );
    MyPrint( y );        // prints 3 4

    int z = 42;
    MyPrint( z );        // prints 42

    return 0;
}