/* File: lambda4.cpp
   
   If you want to modify a captured variable,
   you must use the keyword "mutable".

   Below the captured "count" variable is modified.

*/

#include <iostream>

// must #include <functional> to use std::function< >
//
#include <functional>

using namespace std ;


std::function< int(int) > makeAddXLambda(int x) {
   int count=0 ;
   
   count = 79 ;
   cout << "count = " << count << endl ;

   return [x,count](int n) mutable { 
                             cout << "( count = " << count << ") " ;
                             return n+x+(count++) ;     // modifies captured count
                           } ;
}


int main () {

   std::function< int(int) > add3 = makeAddXLambda(3) ;
   cout << "add3(5): " << add3(5) << endl ;
   cout << "add3(5): " << add3(5) << endl ;
   cout << "add3(5): " << add3(5) << endl ;


   std::function< int(int) > add5 = makeAddXLambda(5) ;
   cout << "add5(8): " << add5(8) << endl ;
   cout << "add5(8): " << add5(8) << endl ;
   cout << "add5(8): " << add5(8) << endl ;

}