Re: More template stuff

From:

"Carl Daniel [VC++ MVP]" <cpdaniel_remove_this_and_nospam@mvps.org.nospam>

Newsgroups:

microsoft.public.vc.language

Date:

Wed, 31 May 2006 14:58:55 -0700

Message-ID:

<erobj0PhGHA.5104@TK2MSFTNGP04.phx.gbl>

"Murrgon" <murrgon@hotmail.com> wrote in message
news:u7uIlOPhGHA.2188@TK2MSFTNGP04.phx.gbl...

Okay I can't get this to compile:

//
===========================================================================
#include <math.h>

template<typename NUMTYPE> class NumPair
{
  public:
    NUMTYPE x, y;

    NumPair(NUMTYPE xVal = 0, NUMTYPE = yVal) : x(xVal), y(yVal)
    {
    }

    // Generic IsZero()
    bool IsZero() const
    {
      return 0 == x && 0 == y;
    }

    // Specialized IsZero() for float types
    bool IsZero<float>() const
    {
      return 0.000001f >= abs(x) && 0.000001f >= abs(y);
    }

IsZero isn't a template and can't be specialized - it's an ordinary member
of a template class (there's a difference!). To specialize IsZero you need
to specialize the entire class.

};
//
===========================================================================

however it works if I pull the specialized version of IsZero() outside
of the class definition like this:

template<> bool NumPair<float>::IsZero() const
{
return 0.000001f >= abs(x) && 0.000001f >= abs(y);
}

This shouldn't compile either - IsZero is not a template and cannot be
specialized. What compiler are you using?

Is there some way to specify the syntax to get the first example to
compile,
or am I stuck using the method outside the scope of the class definition?

Neither of the approaches you've posted is valid C++ code. I'd suggest
moving IsZero outside the class, making an ordinary template function and a
non-template overload for float types (and perhaps another for double).

-cd