An array pointer comparison error

Question

Its a simple insert and display elements in an array code that I have done.

'    

#include<stdio.h>
int insert(int *arr);
int display(int *arr);
int main()
{

int MAX=5;
int arr[MAX];
insert(arr);
display(arr);
}
int insert(int *arr)
{
int n,i;
printf("Enter how many elements");
scanf("%d",&n);
 for(i=0;i<n;i++)
        {
            printf("Enter value at arr[%d]\n",i);
            scanf("%d",&arr[i]);
        }
return *arr;
}


int display(int *arr)
{
        int i;
        printf("The values are::");
        for(i=0;arr[i]!=NULL;i++)//This loop is giving some trouble
        {
                printf("\n a[%d]->%d \n",i,arr[i]);
        }
        return *arr;
}

'

Output:: In function 'display': prog.c:33:24: error: comparison between pointer and integer for(i=0;arr[i]!=NULL;i++) ^ This is the error am not able to solve.

I loose the enthusiasm to read the code when i see bad formatting. sigh. — Haris, Oct 26 '15 at 17:49
I loose the enthusiasm to read the code when i see line numbers that mean nothing in an SO code block. — Martin James, Oct 26 '15 at 17:51
I am new to the site.Don't know much about the pattern in which code must be presented here. — Oswarld, Oct 26 '15 at 17:51
Why do you think `integer array` will be `null terminated` ? — ameyCU, Oct 26 '15 at 17:52
@Oswarld Calculate `n` in `main` and pass along in the function , Like this- `int n = sizeof(arr)/sizeof(arr[0]);` . Pass `n` to functions with array and use it in loop . — ameyCU, Oct 26 '15 at 17:58

Haris · Answer 1 · 2015-10-26T18:00:01.463

You have multiple things to be corrected in your code, but the error that you are getting is due to comparison between pointer (NULL) and an int arr[i]

for(i=0;arr[i]!=NULL;i++)

Your integer array arr does not have any NULL element in the end which can be compared. Perhaps you are confused between string and integer arrays.

Another thing that can be changed in your code, is the return type of your functions insert() and delete(). You are not recieveing the return values and thus its better to keep them void.

A Suggestion

Return n from the insert() function, receive it in main(). Then send it to the display() function along with the array, then use that in the for loop.

Best way to know the number of elements in an array that you are passing to a function is sending it to that function along with the array.

score 0 · Answer 2 · answered Oct 31 '15 at 06:07

'
#include<stdio.h>
#include<stdlib.h>
int MAX=5,i,pos,val;
int display(int *arr);
int main(void)
{
    int arr[MAX];
    display(arr);
}

int display(int *arr)
{
    printf("The values are::");
    for(i=0;i<MAX;i++)
    {
           printf("\n a[%d]-->%d ",i,arr[i]);
    }
        return *arr;
}'

To avoid use of too many variables I continued the use of 'MAX' in the code.Making it global and it worked!!

An array pointer comparison error

2 Answers2