How can I avoid using globals? - c

Question

I have this program that I try to run:
void get_set(int size, int arr[])
{
int i;
printf("Enter number of values to the array : \n");
scanf("%d", &size);
printf("\n");
for (i = 0; i < size; i++)
{
printf("Value at %dth place is : \n", i + 1);
if (scanf("%d", &arr[i]) == EOF)
{
break;
}
}
}
void print_set(int size, int arr[])
{
int i, flag = 0;
if (flag == 0)
{
printf("\nOriginal array is : ");
for (i = 0; i < size; i++)
{
printf("%d,", arr[i]);
}
printf("\n");
}
else
{
printf("\nArray after deleting duplicates : ");
for (i = 0; i < size; i++)
{
printf("%d,", arr[i]);
}
printf("\n");
}
flag + 1;
}
void RemoveDuplicates(int size, int arr[])
{
int i, j, k;
for (i = 0; i < size; i++)
{
for (j = 0; j < i; j++)
{
if (arr[i] == arr[j])
{
size--;
for (k = i; k < size; k++)
{
arr[k] = arr[k + 1];
}
i--;
}
}
}
}
int main()
{
int size = 0;
int arr[64] = {0};
get_set(size, arr);
print_set(size, arr);
RemoveDuplicates(size, arr);
print_set(size, arr);
return 0;
}
In short, the program gets an array with values that I entered, and passes it thru other functions.
I can't get it to pass the array and size to other functions. I am trying to avoid globals; what am I doing wrong?

Answer 1

The size variable in main is passed by value to get_set, so it will still be 0 in main. You should have get_set return the size and assign the result to the size variable (or pass size by reference) so that you can pass it to print_set and RemoveDuplicates.
get_set doesn't really need size as a parameter, unless you change it's meaning to indicate the capacity of the array and add error checking to make sure that you don't overflow it.
The arr variable is passed by reference because it is an array which decays into a pointer, so get_set will modify the variable in main.

Answer 2

You could use:
#include <stdio.h>
#include <stdlib.h>
static int get_set(int size, int arr[])
{
int i;
int n;
printf("Enter number of values to the array: ");
fflush(stdout); // Usually not strictly necessary, but ensures the prompt appears
if (scanf("%d", &n) != 1)
{
fprintf(stderr, "Invalid number entered\n");
exit(EXIT_FAILURE);
}
if (n > size)
n = size;
printf("\n");
for (i = 0; i < n; i++)
{
printf("Value %d is: ", i + 1);
fflush(stdout);
if (scanf("%d", &arr[i]) != 1)
{
break;
}
}
return i;
}
static void print_set(const char *tag, int size, int arr[])
{
int i;
printf("\n%s: ", tag);
for (i = 0; i < size; i++)
{
printf("%d,", arr[i]);
}
printf("\n");
}
static int RemoveDuplicates(int size, int arr[])
{
int i, j, k;
for (i = 0; i < size; i++)
{
for (j = 0; j < i; j++)
{
if (arr[i] == arr[j])
{
size--;
for (k = i; k < size; k++)
{
arr[k] = arr[k + 1];
}
i--;
}
}
}
return size;
}
int main(void)
{
int arr[64] = {0};
int size = get_set(64, arr); // 64 is the maximum; size contains the actual
print_set("Original array", size, arr);
size = RemoveDuplicates(size, arr);
print_set("Duplicates removed", size, arr);
return 0;
}
None of the functions except main() are called from outside this file; the functions can all be static, therefore.
Example run:
Enter number of values to the array: 12
Value 1 is: 1
Value 2 is: 1
Value 3 is: 1
Value 4 is: 2
Value 5 is: 2
Value 6 is: 3
Value 7 is: 4
Value 8 is: 5
Value 9 is: 99
Value 10 is: 999
Value 11 is: 1
Value 12 is: 1
Original array: 1,1,1,2,2,3,4,5,99,999,1,1,
Duplicates removed: 1,2,3,4,5,99,999,
An alternative redesign of the print_set() function would make the flag in the original code into a static int. However, that is a far less flexible solution than passing the tag string argument to the function. Static variables inside functions are occasionally useful, but they should be regarded with a jaundiced eye and avoided when possible, just as global variables should be avoided when possible.