Lambda as function parameter

Question

What\'s the notation for declaring a lambda variable, or function parameter, without the use of auto or templates? Is there any way to do so? Or does the compil

Answer 1

You can use a polymorphic wrapper for a function object. For example:

#include <functional>

std::function<double (double, double)> f = [](double a, double b) { return a*b };

Answer 2

Lambdas may hold state (like captured references from the surrounding context); if they don't, they can be stored in a function pointer. If they do, they have to be stored as a function object (because there is no where to keep state in a function pointer).

// No state, can be a function pointer:
int (*func_pointer) (int) = [](int a) { return a; };

// One with state:
int b = 3;
std::function<int (int)> func_obj = [&](int a) { return a*b; };