Thread: A question from a newbie regarding nested function

Thank Adak for your quick reply but it's not yet working or may be I couldn't understand you what you wanted to mean. Could you explain it again?

There's no nested function in C.
C compiler don't know the return type of function get_sqr(). and assumes that your function returns int type.
You can either define the function or prototype function before calling it.

Code:

int get_sqr(void);  
// then call it.
or 
int get_sqr(void)
{
   ...
} 
// then call it

Thanks a bunch Adak...it works!!!

Good eye as always, Bayint!

Thanks Bayint Naung and Elysia for leaving useful comments

Function prototype - Wikipedia, the free encyclopedia

That Bayint is EVERYWHERE!

Code:

#include "stdio.h"

int get_sqr(void);   /* <----the function definition or prototype */

int main()
{
   int sqr;
   sqr = get_sqr();

   printf("square: %d", sqr);

   return 0;
}

int get_sqr(void)  /* <---the function declaration */
{
   int num;

   printf("enter a number: ");
   scanf("%d", &num);
   return(num*num);
}

You can get away without a function definition IF the function is listed in your program, before the main() function. It makes for nasty looking code to study, imo, and your coding improves when you have a real prototype or definition for each function.

The easy way to get your function definitions right, is to just copy the function declaration in your editor. Then move to the area above main(), and paste it into place. Now remove the { from the end of the line (if present), and add a semi-colon ; right at the end of the line.

The function definition MUST match the function declaration, unless your compiler accepts some default values and your function happens to match those default values.
Don't rely on default values for function definitions or function declarations - be specific.

Thanks again Adak. I'm trying to understand things you've posted.
Thanks Bayint too

Strictly,

You can get away without a function definition IF the function is listed in your program, before the main() function

It should read as before the caller(use of. in case of function pointer function.

Originally Posted by Sharifhs

Dear Adak, please forgive my ignorance, but just for understanding, could you tell me what is a prototype and where is it used in this program?

A prototype is setting the interface for the function before it's used. Basically it's saying what type of value the function receives(arguments), what value it returns and of course the name of the function.

As its easier to explain in code:

Code:

#include<stdio.h>
int calculator(int, int); // Prototype - returntype name(argument/s)
int main()
{
    printf("Please insert two factors to multiply.\n The first:");
    int factorOne, factorTwo;
    scanf("d%", &factorOne);
    printf("The second: ");
    scanf("d%", &factorTwo);
    int product = calculator(factorOne, factorTwo); // Functioncall
    printf("The product of the factors multiplied is: d%", &product);
    getchar();
    return 0;
}
int calculator(int factorOne, int factorTwo)
{
    return factorOne * factorTwo;
}