C Substring Function <Resolved />

[señorbadger]

Hello i have tried to write a substring function in C

but it wont compile

i still learning C but can someone help me get this working please

#include <stdio.h>
#include <string.h>

typedef char* string;


string substring(string haystack,int start,int length)
{
char* substr;
int c, i;
  if (start > strlen(haystack) || length > strlen(haystack) || (start + length) > strlen(haystack))
    {
      return(0);
    }
    else
    {
    i = 0;
      for(c=start;c<(start + length);c++)
        {
          substr[i] = haystack[c];
          i++;
        }
      return(substr);
    }
}