CODEWITHSUNDEEP
c++templates
harsha
harsha

Reputation: 41

deciding a template type depending on a another template type

Can I assign template type say T a type, depending on another template type say U something like this inside a function.

typename <class T, class U>
func(U var)
{
...

if(U == int) //this can be replaced with std::is_same<U, int>
{
    T = flaot; //instead int/float i have my own data types

}
...
}

Is this possible.. if so how is it done

Upvotes: 1

Views: 1273

Answers (1)

Aconcagua
Aconcagua

Reputation: 25536

Not sure if it is what you want, but you might try this:

template <typename T>
class Selector; // implement this one as well, if you want to have a default...

template <> class Selector<int> { public: using Type = ClassX; };
template <> class Selector<double> { public: using Type = ClassY; };

template<typename U>
void func(U var)
{
    using T = typename Selector<U>::Type;
};

Variant:

template<typename U, typename T = typename Selector<U>::Type>
void func(U var) { }

This would allow to replace the selected type, if need be:

func(12);              // uses default: ClassX
func<int, ClassZ>(10); // replace ClassX with ClassZ

Upvotes: 4

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