error while generating pascal triangle

Question

This is my code to generate Pascal's triangle in C language.

#include<stdio.h>
#include<conio.h>

void main()
{
    int i, n, c;
    scanf("%d", &n);
    for (i = 0; i < n; i++)
    {
        for (c = 0; c <= (n - i - 2); c++)
            printf(" ");
        for (c = 0; c <= i; c++)
            printf("%ld", factorial(i) / (factorial(c)*factorial(i - c)));
        printf("\n");
    }
    getche();
}

long factorial(int n)
{
    int c;
    long res = 1;
    for (c = 1; c <= n; c++)
        res = res*c;
    return(res);
}

On compilation it shows two errors:

conflicting types for 'factorial'
previous implicit declaration of 'factorial' was here

What is my mistake here?

score 1 · Accepted Answer · edited May 23 '17 at 12:11

1

conflicting types for 'factorial'
previous implicit declaration of 'factorial' was here

Both errors refers to one thing: The function factorial shall be declared before used.
Simply move the definition before main or write a declaration for it before main.

I'd not write a detailed explanation for you as there're already some, e.g. What is the difference between a definition and a declaration?

edited May 23 '17 at 12:11

Community

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answered Oct 10 '14 at 07:17

starrify

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@shri_wahal My pleasure to help. :) – starrify Oct 10 '14 at 07:28

score 0 · Answer 2 · answered Oct 10 '14 at 07:18

You are using factorial in main before you define it. This is legal in C, but makes the compiler guess that your function returns an int. However, when reaching the definition of factorial, the compiler notices that it returns, actually, a long, which causes the error.

You can fix this in two ways:

Swap the definitions of main and factorial or
Introduce a forward declaration of factorial before definition of main by adding long factorial(int n);.

error while generating pascal triangle

2 Answers2