use of undeclared identifier 'arr' - c

Question

I'm trying to have some practice with C using Xcode, but got stock with some error.
The code is as follows:
#include <stdio.h>
#include <stdlib.h>
/* move previous elements down until insertion point reached */
void shift_element (unsigned int i ) {
int ivalue;
// guard against going outside array
for (ivalue = arr[i]; i && arr[i-1] > ivalue; i--) {
arr[i] =arr[i-1]; // move element down
arr[i] = ivalue; // insert element
}
}
int main(int argc, const char * argv[]) {
unsigned int arr[5] = {2,4,5,3,6};
shift_element(3);
// print arr
int i;
for (i=0;i < (sizeof (arr) /sizeof (arr[0]));i++) {
printf("%d\n",arr[i]);
}
return 0;
}
But it results in an error saying 'use of undeclared identifier 'arr''
I searched previous questions with the same subject but could not find a proper answer that would solve my problem.
I would be so happy if somebody can help.
Cheers

Answer 1

The arr variable isn't in scope of the shift function. You have to pass it in as a parameter.

Answer 2

You forgot to declare your 'arr'.
Here is a very good answer explaining the various way do to that : How to initialize all members of an array to the same value?
EDIT : Didn't see you declared it in the function below. As the other answer says, you have to pass it as a parameter tho.

Answer 3

Your problem lies in variable accessibility. When you define a variable in the main function it is only accessible in the function in which it was defined. You to try access the array in the shift_elements function which is causing your issue.
To fix this you can either make the arr variable global or pass it in as an argument to your shift_elements(function). I coded a quick correction doing the later because its good practice to avoid global variables when possible.
#include <stdio.h>
#include <stdlib.h>
/* move previous elements down until insertion point reached */
void shift_element (unsigned int i, int[] arr) {
int ivalue;
// guard against going outside array
for (ivalue = arr[i]; i && arr[i-1] > ivalue; i--) {
arr[i] =arr[i-1]; // move element down
arr[i] = ivalue; // insert element
}
}
int main(int argc, const char * argv[]) {
unsigned int arr[5] = {2,4,5,3,6};
shift_element(3, arr);
// print arr
int i;
for (i=0;i < (sizeof (arr) /sizeof (arr[0]));i++) {
printf("%d\n",arr[i]);
}
return 0;
}
For more information on types of variables look here: http://www.mathcs.emory.edu/~cheung/Courses/255/Syllabus/1-C-intro/kinds-vars.html

Answer 4

Just to share with those future possible readers, the correct code would be:
#include <stdio.h>
#include <stdlib.h>
/* move previous elements down until insertion point reached */
void shift_element (unsigned int i, unsigned int *arr ) {
int ivalue;
// guard against going outside array
for (ivalue = arr[i]; i && arr[i-1] > ivalue; i--)
arr[i] = arr[i-1]; // move element down
arr[i] = ivalue; // insert element
}
int main(int argc, const char * argv[]) {
unsigned int arr[5] = {2,4,5,3,6};
// print arr
int i;
for (i=0;i < (sizeof (arr) /sizeof (arr[0]));i++) {
printf("%d\n",arr[i]);
}
shift_element(3, arr);
// print arr
for (i=0;i < (sizeof (arr) /sizeof (arr[0]));i++) {
printf("%d\n",arr[i]);
}
return 0;
}