currying.cpp

// Run online: https://eval.in/506636
#include <iostream>
#include <functional>

// curries any function from (int, int) -> int into int -> (int -> int)
auto curry(int (*func)(int, int)) -> std::function<std::function<int (int)> (int)> {
  return [func] (int x) {
    return [func, x] (int y) {
      return func(x, y);
    };
  };
}

int main (int argc, char ** argv) {
  auto add = [] (int x, int y) -> int { return x + y; };
  auto mult = [] (int x, int y) -> int { return x * y; };
  auto inc = curry(add)(1);
  auto doub = curry(mult)(2);
  std::cout << "     2 incremented is: " << inc(2) << std::endl;
  std::cout << "         8 doubled is: " << doub(8) << std::endl;
  std::cout << "the sum of 2 and 3 is: " << add(2, 3) << std::endl;
  std::cout << "the sum of 2 and 3 is: " << curry(add)(2)(3) << std::endl;
  return 0;
}

/* Output:
     2 incremented is: 3
         8 doubled is: 16
the sum of 2 and 3 is: 5
the sum of 2 and 3 is: 5
*/