How can currying be done in C++?

Question

What is currying?

How can currying be done in C++?

Please Explain binders in STL container?

Answer 1

Other answers nicely explain binders, so I won't repeat that part here. I will only demonstrate how currying and partial application can be done with lambdas in C++0x.

Code example: (Explanation in comments)

#include 
#include 

using namespace std;

const function & simple_add = 
  [](int a, int b) -> int {
    return a + b;
  };

const function(int)> & curried_add = 
  [](int a) -> function {
    return [a](int b) -> int {
      return a + b;
    };
  };

int main() {
  // Demonstrating simple_add
  cout << simple_add(4, 5) << endl; // prints 9

  // Demonstrating curried_add
  cout << curried_add(4)(5) << endl; // prints 9

  // Create a partially applied function from curried_add
  const auto & add_4 = curried_add(4);
  cout << add_4(5) << endl; // prints 9
}