Functional programming with c , integer types

Functional.c

#include<stdio.h>
#include<stdlib.h>

#define arrlen(x) (sizeof(x)/sizeof((x)[0]))

int callback( int i ) {
  return i * 2;
}

int callback_filter( int i ) {
  return i % 2 == 0;
}

void print_R( int i ) {
  printf("%d, ", i);
}

int* map( int src[], size_t count, int(*cb)(int)  ) {
  int i;
  int *dest;
  dest = (int *) calloc( count, sizeof( int ) );

  for( i = 0; i < count; i++ ) {
    dest[ i ] = (*cb)(src[ i ]);
  }
  return dest;
}

int* filter( int src[], size_t count, int(*cb)(int) ) {
  int i;
  int c = 0;
  int *dest;
  dest = (int *) calloc( count, sizeof( int ) );

  for( i = 0; i < count; i++ ) {
    if( (*cb)(src[ i ] ) > 0) {
      dest[ c ] = src [ i ];
      ++c;
    }
  }
  return dest;
}

int* each( int *src, size_t count, void(*cb)(int)) {
  int i;
  for(i = 0; i < count; i++) {
    (*cb)(src[ i ]);
  }
  return src;
}

int main( ) {
  int array[9] = {1,2,3,4,5,6,7,8,9};
  int *result;
  int i;
  size_t len = arrlen( array );

  result = map( array, len, callback );

  each( result, len, print_R);
  free(result);

  printf("\n");

  result = filter( array, len, callback_filter );

  each( result, len, print_R);
  free(result);

  return 0;
}