Map function in C ++ with templates

Question

I am trying to learn patterns in C ++, and one of the things I tried was to encode a map function, such as the ones you usually find in functional languages. The idea was something like this:

template <class X> X * myMap(X * func(X), X * array, int size)
    {
      X * temp;
      for(int i = 0, i < size, i++) {temp[i] = (*func)(array[i]);}
      return temp;
    }

But when I try to use this in:

int test(int k) { return 2 * k;}
int main(void)
{
   int k[5] = {1,2,3,4,5};
   int *q = new int[5];
   q = myMap(&test, k, 5);
   for(int i=0; i<5; i++) {cout << q[i];}
   delete [] q;
   return 0;
}

When compiling, I got a type mismatch error:

 main.cpp:25: error: no matching function for call to ‘myMap(int (*)(int), int [5], int)’

I tried changing it to:

int main(void)
{
   int *k = new int[5];
   int *q = new int[5];
   for(int i=0; i<5;i++) {k[i] = i;}
   q = myMap(&test, k, 5);
   for(int i=0; i<5; i++) {cout << q[i];}
   delete [] q;
   return 0;
}

The error message changes to:

 main.cpp:26: error: no matching function for call to ‘myMap(int (*)(int), int*&, int)’

This is probably something very wrong, but I can not find where.

EDIT: errors in which: 1) I was silent about the function pointer. This is X (* func) (X) instead of X * func (X). 2) forgot to highlight temp. Need to do X * temp = new X[size]. 3) are there more errors?

Answer 1

. :

template <class X> 
X* myMap(X (* func)(X), X * array, int size)
{
    ...
}

, , , ++ ().

template <class X, class F> 
X* myMap(F func, X * array, int size)
{
   ...
}

Answer 2

X * func(X) , , . X (*func)(X).

Answer 3

. parens X(*func)(X). , :

#include <iostream>
using namespace std;


template <class X> X * myMap(X(*func)(X), X * array, int size)
    {
      X * temp;
      for(int i = 0; i < size; i++) {temp[i] = (*func)(array[i]);}
      return temp;
    }

int test(int k) { return 2 * k;}
int main(void)
{
   int k[5] = {1,2,3,4,5};
   int *q = new int[5];
   q = myMap(&test, k, 5);
   for(int i=0; i<5; i++) {cout << q[i];}
   delete [] q;
   return 0;
}

Answer 4

MyMap, MyMap. q = MyMap (.....)