Thread: C Functions how do i put this in a function

Ive been told to put the following code into a function and yet when i try since it is 3 arrays i cant get it to work at all. Any ideas to get me started on this?
I tried using a function like this

Code:

void funct1(int x[], y[], z[]);
{
for (i=0; i<funct1; i++)
return      x[i] = i;
return       y[i] = i;
return       z[i] = i;
}

Code:

#include <stdio.h>
#include <stdlib.h>

int main()
{
   int x[10], y[15], z[20];
   int i, sumx, sumy, sumz;

   for (i=0; i<10; i++)
      x[i] = i;

   for (i=0; i<15; i++)
      y[i] = i;

   for (i=0; i<20; i++)
      z[i] = i;

   sumx = 0;
   for (i=0; i<10; i++)
      sumx = sumx + x[i];

   sumy = 0;
   for (i=0; i<15; i++)
      sumy= sumy + y[i];

   sumz = 0;
   for (i=0; i<20; i++)
      sumz = sumz + z[i];

   printf ("The sum of the x array = %d\n", sumx);
   printf ("The sum of the y array = %d\n", sumy);
   printf ("The sum of the z array = %d\n", sumz);

   system("PAUSE");
   return 0;
}

It works fine with no function but im told a function would make it easier to read and faster to process although it seems pretty fast to me.

I'm new to C and working through a workbook and don't understand functions real well yet.

Thank you for any assistance.

It sounds like you are being asked to make a function to sum the arrays. I could be wrong, but....

Create a function that you pass into it one of the arrays and the array length, and it should return an integer which is the sum.

The idea behind functions is to call it in main(), for example

Code:

val = test(p1, p2);  // call the function test, passing in p1 and p2, returns val

Then the function would be defined as:

Code:

int test(int var1, int var2)
{
    int rv;   // the return value
// code that calculates rv
    return rv;
}

int: the type of value returned
test: the function name
(int var1, int var2): two integers are passed into the routine. var1 will contain the value of p1 from main, var2 will be p2
the value rv will be returned and placed in val

Also... if you want to write a function which alters mulitple variables from the calling function you can just pass pointers to those variables instead (obviously multiple return statements from a single function aren't allowed).

Code:

#include <stdio.h>

void assign_ints( int *a, int *b )
{
  *a = 1;

  b[0] = 10;
  b[1] = 20;
}

int main()
{
  int a=0, b[2]={0,0};

  assign_ints( &a, b );

  printf( "\na: %d", a );
  printf( "\nb: %d %d\n\n", b[0], b[1] );

  return 0;
}

Originally posted by DrZoidberg

Code:

    system("PAUSE");

Why do so many people use this command to stop a program? It uses a system call into the OS and may not work on all systems (I think), whereas all C compilers have defined getchar() which would work without OS intervention. And it's also easier to type.

Is this being taught in schools?

getchar() alone could catch any single stray character which may or may not be desired. Another form. ch is an int.

while(ch=getchar() != '\n' || ch != EOF);