A decidely non-challenging task to highlight a potential difference between programming languages.

Using a straightforward longhand loop as in the JavaScript and Phix examples below, show the locations of elements which are identical to the immediately preceding element in {1,2,2,3,4,4,5}. The (non-blank) results may be 2,5 for zero-based or 3,6 if one-based. 

The purpose is to determine whether variable declaration (in block scope) resets the contents on every iteration.

There is no particular judgement of right or wrong here, just a plain-speaking statement of subtle differences.

Should your first attempt bomb with "unassigned variable" exceptions, feel free to code it as (say)

 // int prev // crashes with unassigned variable
    int prev = -1 // predictably no output

If your programming language does not support block scope (eg assembly) it should be omitted from this task.

public class VariableDeclarationReset {
    public static void main(String[] args) {
        int[] s = {1, 2, 2, 3, 4, 4, 5};
 
        // There is no output as 'prev' is created anew each time
        // around the loop and set to zero.
        for (int i = 0; i < s.length; ++i) {
            int curr = s[i];
            int prev = 0;
//          int prev; // triggers "error: variable prev might not have been initialized"
            if (i > 0 && curr == prev) System.out.println(i);
            prev = curr;
        }
 
        int gprev = 0;
 
        // Now 'gprev' is used and reassigned
        // each time around the loop producing the desired output.
        for (int i = 0; i < s.length; ++i) {
            int curr = s[i];
            if (i > 0 && curr == gprev) System.out.println(i);
            gprev = curr;
        }
    }
}