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template<> struct PromoteTraits<ArithmeticType1, ArithmeticType2> |

Binary traits for promotion of arithmetic objects.

#include <vigra/numerictraits.hxx>

This traits class is used to determine the appropriate result type of arithmetic expressions which depend of two arguments. Consider the following function:

        template <class T>
        T min(T t1, T t2)
        {
            return (t1 < t2) ? t1 : t2;
        }

This template is only applicable if both arguments have the same type. However, sometimes we may want to use the function in cases where the argument types differ. The we can deduce the approrpiate return type by using `PromoteTraits`:

        template <class T1, class T2>
        typename vigra::PromoteTraits<T1, T2>::Promote
        min(T1 t1, T2 t2)
        {
            return (t1 < t2) ? vigra::PromoteTraits<T1, T2>::toPromote(t1) :
                               vigra::PromoteTraits<T1, T2>::toPromote(t2);
        }

In addition, the traits class provide static functions to cast the arguments to the promote type. For example, if `T1` were `int` and `T2` were `float`, the `Promote` type would be `float`. The following members are defined in `PromoteTraits<ArithmeticType1, ArithmeticType2>`:

`typedef ... Promote;` | promote type
`static Promote toPromote(ArithmeticType1 v);` `static Promote toPromote(ArithmeticType2 v);` | convert to `Promote` type

PromoteTraits for the built-in types are defined in #include <vigra/numerictraits.hxx>

Namespace: vigra

© Ullrich Köthe (ullrich.koethe@iwr.uni-heidelberg.de) Heidelberg Collaboratory for Image Processing, University of Heidelberg, Germany | html generated using doxygen and Python vigra 1.7.1 (3 Dec 2010)