Output of the C program?

thelink123 · 06-08-2009, 07:55 PM

Hi,

Please see the first program below :

Code:

/*1*/int main()
/*2*/{
/*3*/   extern int fun(float);
/*4*/   int a;
/*5*/   a = fun(3.14);
/*6*/   printf("%d",a);
/*7*/}

/*8*/int fun(aa)
/*9*/float aa;
/*10*/{
/*11*/   return ((int)aa);
/*12*/}

This code when compiled gives the following errors:

1. conflicting types for 'fun' at line no: 9

2. previous declaration of 'fun' was here at line no: 3

Why is this happening??

If i modify the above program as shown in the second program below :

Code:

/*1*/int main()
/*2*/{
/*3*/   extern int fun(int); /* float replaced by int */
/*4*/   int a;
/*5*/   a = fun(3.14);
/*6*/   printf("%d",a);
/*7*/}

/*8*/int fun(aa)
/*9*/int aa; /* float replaced by int */
/*10*/{
/*11*/   return ((int)aa);
/*12*/}

This code when compiled gives no errors.

Please tell me why the difference occurs between the first and second program??

thanks
thelink.

jiml8 · 06-08-2009, 08:06 PM

It also works if your function declaration is int fun(float aa) {

And it works if you move your prototype statement out of your main program and have it outside of any program module.

That is interesting. You shouldn't be prototyping from within your main program.

jamescondron · 06-08-2009, 08:09 PM

Incidentally, what are you aiming to do with this code? What do you expect it to do? What would you like it to do? I mean, your first issue is reasonably simple, though I'd ask your Instructor/ Lecturer, and your second is a follow on from the first.

EDIT: Next time you post code, don't put those horrible line numbers in please, I know you may want the line numbers in your code, but they hamper readability

pixellany · 06-08-2009, 10:20 PM

Moved: This thread is more suitable in <Programming> and has been moved accordingly to help your thread/question get the exposure it deserves.

noctilucent · 06-09-2009, 02:19 AM

Code:

int main()
{
        extern int fun();
        /* ... */

It is left as an exercise to the OP to research old-style C function prototypes / definitions and understand why:

1. The above works.
2. Having "aa" of type int yields no errors.

thangappan · 06-09-2009, 05:49 AM

It is interesting.But syntactically it is funny.

Traditionally we define a function as

return_type function_name(parameters with its data type)
{
return value;
}

This is first time I have seen the code like this.

In your program if you follow the unique steps there will not be any error.

You are specifying the prototyping inside the function.In the case of integer it will not consider( This is my assumption).

Try to follow the coding rules.

Anyway I appreciate your curiosity.

thelink123 · 06-09-2009, 08:44 PM

Ya the question i asked is indeed very interesting. But as programmers we should have an answer for this, if the code i have given is in C language. The forum members have no right to question my curiosity. Its better not to have an opinion if one cannot find the solution(Referring to the boorish words from jamescondron)

Anyways thanks for all the replies. But in future kindly do not question the sincerity of a programmer. Find answers which are helpful.

Thanks to moderator for moving the Post to the correct place.

The bottom line is that LQ still cannot answer my question. Waiting for the answers.

All the best
thelink

Sergei Steshenko · 06-09-2009, 09:48 PM

Quote:

Originally Posted by thelink123

Hi,

Please see the first program below :

Code:

/*1*/int main()
/*2*/{
/*3*/   extern int fun(float);
/*4*/   int a;
/*5*/   a = fun(3.14);
/*6*/   printf("%d",a);
/*7*/}

/*8*/int fun(aa)
/*9*/float aa;
/*10*/{
/*11*/   return ((int)aa);
/*12*/}

This code when compiled gives the following errors:

1. conflicting types for 'fun' at line no: 9

2. previous declaration of 'fun' was here at line no: 3

Why is this happening??

If i modify the above program as shown in the second program below :

Code:

/*1*/int main()
/*2*/{
/*3*/   extern int fun(int); /* float replaced by int */
/*4*/   int a;
/*5*/   a = fun(3.14);
/*6*/   printf("%d",a);
/*7*/}

/*8*/int fun(aa)
/*9*/int aa; /* float replaced by int */
/*10*/{
/*11*/   return ((int)aa);
/*12*/}

This code when compiled gives no errors.

Please tell me why the difference occurs between the first and second program??

thanks
thelink.

Because default type in "C" is int, so

/*3*/ extern int fun(float);

contradicts

/*8*/int fun(aa)

in function argument type, i.e. typeless aa mean it is int, and on line #3 you declared argument to be of float.

thelink123 · 06-09-2009, 11:08 PM

Thats it...This solves the problem i think...thanks Sergei Steshenko for the answer

Thanks LQ

Regards
thelink