CODEWITHSUNDEEP
c
IggY
IggY

Reputation: 3125

Factorial in recursive C : type issue

I have a problem while compiling this code on gcc 4.7.2 (Ubuntu Server 12.10)

#include <stdio.h>

int main()
{
  long int facto = 30;
  printf("%ld\n", fact(facto, facto - 1);
}
long int fact(long int n, long int a)
{
   if (a == 1)
      return (n);
   fact(n * a, a - 1);
}

I know this can be done with a one argument function but it's not the point here.

The error I got is : conflicting type for 'fact' (line of function declaration) previous implicit declaration of fact here (line with printf)

Upvotes: 0

Views: 400

Answers (2)

simonc
simonc

Reputation: 42175

You need a forward declaration for fact before you call it from main

long int fact(long int n, long int a); // forward declaration
int main()
{
  long int facto = 30;
  printf("%ld\n", fact(facto, facto - 1);
}
long int fact(long int n, long int a) // actual function

You could just move the implementation of fact above main in this case. Note however that this approach won't scale to more complex programs with more longer functions calling into each other.

ADD Your factorial function is wrong. Here is the corrected version

long int fact(long int n)
{
   if (a == 1)
      return (n);
   return n * fact(n - 1);
}

Upvotes: 6

user1943931
user1943931

Reputation: 

#include <stdio.h>
long int fact(long int n, long int a);
int main()
{
  long int facto = 30;
  printf("%ld\n", fact(facto, facto - 1);
}
long int fact(long int n, long int a)
{
   if (a == 1)
      return (n);
   fact(n * a, a - 1);
}

You need a function prototype, which is basically the first line of the function with a semicolon. This will tell the compiler that this function exists.

Upvotes: 0

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