Map of template functions

Question

I want to make a std::map with std::string keys that contains functions. These functions should be templates in order to work with different numeric values:

template <typename T> T (*pfunc)(T,T);

The map declarations looks like this:

std::map<std::string, pfunc> funcMap;

I know I need a template argument list for pfunc but I don't really know how to do it.

[EDIT]

Taking in count the comments. I would like to be able to: Create a function template as:

template <typename T> 
T myMax(T x, T y) 
{ 
   return (x > y)? x: y; 
} 

or

template <typename T> 
T myMin(T x, T y) 
{ 
   return (x < y)? x: y; 
} 

• Then add it to my map: funcMap["myMax"] = myMax; or funcMap["myMin"] = myMin;
• And use it as:

funcMap["myMax"]<int>(3,4);
funcMap["myMax"]<float>(3.1,4.5);
funcMap["myMin"]<int>(3,4);
funcMap["myMin"]<float>(3.1,4.5);

• Is this posible? any better ideas?

Answer 1

I think the best you will get is

template <typename T> 
T myMax(T x, T y) 
{ 
   return (x > y)? x: y; 
} 

template <typename T> 
T myMin(T x, T y) 
{ 
   return (x < y)? x: y; 
} 

template <typename T> using pfunc = T(*)(T, T);

template <typename T> std::map<std::string, pfunc<T>> funcMap = { 
    { "myMax", myMax }, 
    { "myMin", myMin } 
};

You will need to define all your function templates before defining funcMap, or limit yourself to a pre-determined set of types. I don't know of a way of populating infinite funcMap instantiations with infinite function template instantiations after it's definition.