standard C operator as parameter to template function - c++

On Fri, 22 Jun 2007 11:31:11 +0200, Klaus Schneider wrote:

> Dear newsgroup,
>
> I want to call a template function with a standard operator (+, /, -, * for
> double) as parameter. Here is a minimal example:
>
> template <typename T>
> T opIf(T val1, T val2, T (*op)(T,T) )
> {
> if (val2 != 0)
> return op(val1, val2);
> else
> return (T)0;
> }
>
> How can I call this function with e.g. the standard / operator?
>
> double res = opIf(10., 5., operator/);
> or similar does not work.
>
> Thanks a lot,
> Klaus
>

template <typename T, typename Functor>
T opIf(T val1, T val2, Functor op )
{
if (val2 != 0)
return op(val1, val2);
else
return (T)0;
}

#include <functional>
#include <iostream>

int main()
{
std::cout<<opIf(6,3,std::divides<int>())<<std::endl;
std::cout<<opIf(6,3,std::multiplies<int>())<<std::endl;
std::cout<<opIf(6,3,std:lus<int>())<<std::endl;
std::cout<<opIf(6,3,std::minus<int>())<<std::endl;
return 0;
}

--
Obnoxious User

Klaus Schneider wrote:

> Dear newsgroup,
>
> I want to call a template function with a standard operator (+, /, -, *
> for double) as parameter. Here is a minimal example:
>
> template <typename T>
> T opIf(T val1, T val2, T (*op)(T,T) )
> {
> if (val2 != 0)
> return op(val1, val2);
> else
> return (T)0;
> }
>
> How can I call this function with e.g. the standard / operator?
>
> double res = opIf(10., 5., operator/);
> or similar does not work.

What about:



template < typename T, typename Op >
T opIf ( T lhs, T rhs, Op op ) {
if ( rhs != T() ) {
return ( op( lhs, rhs ) );
} else {
return ( T() );
}
}

#include <iostream>

int main ( void ) {
std::cout << opIf( 10.0, 5.0, std::divides<double>() ) << '\n';
}



Best

Kai-Uwe Bux

On 6 22 , 5 31 , Klaus Schneider <schnei...@iup.uni-heidelberg.de>
wrote:
> Dear newsgroup,
>
> I want to call a template function with a standard operator (+, /, -, * for
> double) as parameter. Here is a minimal example:
>
> template <typename T>
> T opIf(T val1, T val2, T (*op)(T,T) )
> {
> if (val2 != 0)
> return op(val1, val2);
> else
> return (T)0;
>
> }
>
> How can I call this function with e.g. the standard / operator?
>
> double res = opIf(10., 5., operator/);
> or similar does not work.
>
> Thanks a lot,
> Klaus
>
> --
> Please insert my name and a dot before my email address.

double res = opIf(10., 5., operator/);
operator / is not a global operator..
used std::divides<double> instead.