Auto variable to store function pointer to std::max

Question

I\'m trying to pass function std::max as template parameter to a templated function, but for some reasons compiler prints error that function type cannot be ded

Answer 1

As seen here, std::max<float> isn't a single, unambiguous function. At this point, it's an overload set and there are still two possibilities:

constexpr const float& max( const float& a, const float& b );
constexpr float max( std::initializer_list<float> ilist );

You have two main options:

1. Cast to the appropriate type:

   auto f = static_cast<const float&(*)(const float&, const float&)>(std::max);
   

2. Wrap it in a lambda:

   auto f = [](float a, float b) { return std::max(a, b); };
   // Note there's no by-reference behaviour in this lambda.
   

In the future, it is expected that you will be able to do better. Today, you could emulate such a thing today with a macro (most simply done by making the macro expand into a lambda). I've come across at least one LIFT macro that does this.

Answer 2

std::max has more than one template overloads; you can use static_cast to specify which one should be used.

static_cast may also be used to disambiguate function overloads by performing a function-to-pointer conversion to specific type

e.g.

auto f = static_cast<const float& (*)(const float&, const float&)>(std::max<float>);