Calling function in another file

I am writing a program that takes integers from a user and sorts them in ascending order. I understand the process of most of the steps but our teacher has said that the actual function that determines which of two array elements is larger must be done from another .c file.

I'm not quite sure how the calling of another file works. Here is the code I have so far.

p1.c:

Code:

/* This program in its entirety takes a list of integers from a user and arranges them in ascending
order */


#include<stdio.h>
#include "temp.h"

#define PROMPT "Enter up to 10 integers, ending with -1:"
#define TOO_MANY "Exceeded maximum array size."

main(void)
{
        char input[MAX_NUM + 1] = {'0'};
        int x, i, j, temp1, temp2, temp;

        puts(PROMPT);
        gets(input);



        for(i = 0; i < MAX_NUM; i++)
        {
                for(j = MAX_NUM; j < i; j--)
                {
                        larger(input[i], input[j]);

                        if(temp = input[j])
                        {
                                temp1 = input[i];
                                input[i] = input[j];
                                input[j] = temp1;
                        }

                }

        }

        return 0;
}

temp.h

Code:

#define MAX_NUM 10
int larger(int a, int b);

temp.c

Code:

#include<stdio.h>
#include "temp.h"

int larger(int a, int b)
{
        if(a > b)
        {
                temp = a;

        } else temp = b;

        return temp;

}

The teacher provided us with the temp.h and says that the larger() function must be defined in temp.c. So now that I have that, how do I access the function from p1.c?

And will the 'temp' variable returned in the larger() function be accessible from p1.c in the manner I've written?

Code:

#include "temp.h"

This line indirectly imports the declaration of the function so when you compile it, it knows that there should be a function somewhere with that name and signature. That means you can simply call the function. Use it in every .c file that needs to use that function (or in the case of temp.c where it needs to define the function).

When you compile, you must specify all of the .c files to compile, including the one that has the definition of the function(s) declared in temp.h. The compiler (or perhaps more properly, the linker) is tasked with figuring out how to put it all together.

Ah, thank you MacGyver, it didn't occur to me that I had to compile both .c files. Thanks man

Originally Posted by cashmerelc

And will the 'temp' variable returned in the larger() function be accessible from p1.c in the manner I've written?

You don't use the return value at all within the P1.C source file. You'd have to assign the return value from the function call to one of your variables to use it in some way.

I see, hk, that makes sense.


I've made a few changes to my code and I'm getting a new compiler error.

passing arg 1 of `fgets' makes pointer from integer without a cast

The user is going to enter integers, one at a time with each followed by a return, so I'm trying to use fgets to put each integer into the same array in respective elements and here is what I have.

Code:

 for(i = 0; i < MAX_NUM; i++)
        {
                fgets(input[i], MAX_NUM, stdin);
                nl = strrchr(input, '\n');
                if (nl) *nl = '\0';
        }

I don't understand the error.

input[i] is a char (integer type) but the fgets function accepts a pointer for the first argument, the error is saying you are trying to convert/use the integer value stored in input[i] as a pointer when it isn't and is prompting you that perhaps you might want to use a cast (which you don't in this case) which would suppress that warning/error. fgets is perhaps not the way you want to go here for data input since you'd still have to convert the text entered by the user into a numeric/integer value perhaps using sscanf before storing it in the input array. It occurs to me that your array probably should be an array of ints and not char given what is happening.

main(void) is lacking return type int!
gets is very, very bad! fgets is a better choice.
Read the FAQ for more info or check my signature for links.

> main(void) is NON-standard!

The void as an argument is okay, it's only bad as a return type. The int return type should be explicit, though.

Or maybe I should just mention it's bad practice and it's lacking return type int.

Originally Posted by Elysia

Or maybe I should just mention it's bad practice and it's lacking return type int.

Making the argument(s) of main() explicit is _not_ bad practice. In fact, the C99 Standard explicitly mentions "int main(void)" as an allowed prototype, but not "int main()".

http://faq.cprogramming.com/cgi-bin/...wer=1044841143

You misundestand
main(void) = bad practice
int main(void) = good practice