Thread: User generated functions and interaction between them.

Hello,

I was given a task to construct a program that should look like this:

Code:

<...>
<description of fun1>
<description of fun2>
main(){
<giving the program the initial parameters>;
<fun1(<parameters>);
}

"fun1" (function one) of type void must complete the given task and print out the end results whereas "fun2" provides the side results that are used by "fun1".

I'm struggling to understand how those two functions should interact with each other, especially because the fun1 that requires the results of the fun2 is described before fun2. Also, with a given task, fun2 must send a whole lot of results that fun1 must check and print out whether they meet the conditions. What should be written in order to achieve that?In addition, I would be very grateful if you could tell me how the repeating answers could be eliminated.

So far I only have this:

Code:

#include <stdio.h>

void fun1 (int, int)
{
    if (the "result of fun2"==S)
        {printf("%d %d", i, k);} /*The problem is, I don't know how "i" and "k" should be transfered to this function*/
    
}


int fun2 (int)
{
    int i, k;
    for(i=1; i<=S; i++)
    {
        for(k=1; k<=S; k++)
        {
            return i*k
        }
    }
}




main ()
{
    int S;
    printf("Enter the area of the rectangle.\n");
    scanf("%d\n", &S);
    fun1(S);    
}

The task is to construct a program where a user enters the area of a rectangle and the program prints out all the possible lengths and widths so their product is equal to the given area.

If you have any questions, I'll do my best.
Also, sorry if anything's hard to understand. English isn't my mother tongue.

Have a nice day!

Well normally, you would prototype all the functions first, so the whole problem of how 'who calls who' goes away.

Code:

// these are prototypes
void fun1(int area);
int fun2(int a);

// with prototypes already declared, fun1 can call fun2 even though
// the compiler hasn't seen the code yet.

void fun1( int area ) {
  // do stuff
  answer = fun2(123);
  // do more stuff
}

int fun2 ( int a ) {
  // do stuff
  return 42;
}

You need to pass i and k by reference to function 2. In C all passing is by value, but passing by reference can be simulated by using pointers.

In your case you would move the declaration of i and k to function 1. You would change function 2 to int fun2( int, int*,int* ),and the if statement becomes if( fun2( S, &i, &k ) == whatever). This function returns an int and has what is called two output parameters. It's basically telling fun2 where to find and use i and k. Instead of passing values, we are passing addresses of values.

It's about right, except there is no need for i,k to be pointers in fun2