/* File: lambda3.cpp

One way to return and pass lambda expressions is 
the std::function facility

*/


#include <iostream>

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

using namespace std ;


std::function< int(int) > makeAddXLambda(int x) {
   return [x](int n){ return n+x ; } ;  // capture all by value
}


void apply( std::function< int(int) > f, int A[], int n) {
   for (int i=0 ; i < n ; i++) {
      A[i] = f( A[i] ) ;
   }
}

int main () {

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

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

   int B[10] = { 10, 11, 12, 13, 14, 15, 16, 17, 18, 19} ;

   printf("Before:\n") ;
   for (int i=0 ; i < 10 ; i++) {
      cout << "   B[" << i << "] = " << B[i] << endl ;
   }

   apply (add3, B, 10) ;

   printf("\n\nAfter calling apply(add3, B, 10):\n") ;
   for (int i=0 ; i < 10 ; i++) {
      cout << "   B[" << i << "] = " << B[i] << endl ;
   }

}