• DLearner (46/46) Mar 01 2023 Hi
• Paul Backus (4/11) Mar 01 2023 With `foreach`, you can't reuse an existing variable as the loop
• Salih Dincer (15/20) Mar 02 2023 Or use the `each` template which is almost the same as `foreach`

DLearner <bmqazwsx123 gmail.com> writes:

Hi

Please consider (1):
```
void main() {
    import std.stdio;

    int wk_Idx;

    int[2] IntArr;

    IntArr[0] = 1;
    IntArr[1] = 2;

    for (wk_Idx = 0; wk_Idx <= 1; wk_Idx = wk_Idx + 1) {

       writeln("wk_Idx = ", wk_Idx, " IntArr = ", IntArr[wk_Idx]);
    }
}
```

Now consider (2), which is (1) via assoc. array:
```
void main() {
    import std.stdio;

    int wk_Idx;

    int[int] IntArr;

    IntArr[0] = 1;
    IntArr[1] = 2;

    for (wk_Idx = 0; wk_Idx <= 1; wk_Idx = wk_Idx + 1) {

       writeln("wk_Idx = ", wk_Idx, " IntArr = ", IntArr[wk_Idx]);
    }
}
```

And finally (3) which is (2) via a foreach:
```
void main() {
    import std.stdio;

    int wk_Idx;

    int[int] IntArr;

    IntArr[0] = 1;
    IntArr[1] = 2;

    foreach (wk_Idx; IntArr.keys) {

       writeln("wk_Idx = ", wk_Idx, " IntArr = ", IntArr[wk_Idx]);
    }
}
```

(1) & (2) compile and run with the expected results.
But (3) fails with:
```
Error: variable `wk_Idx` is shadowing variable `for3.main.wk_Idx`
```
Why is this usage wrong?

Paul Backus <snarwin gmail.com> writes:

On Wednesday, 1 March 2023 at 19:05:10 UTC, DLearner wrote:
 (1) & (2) compile and run with the expected results.
 But (3) fails with:
 ```
 Error: variable `wk_Idx` is shadowing variable 
 `for3.main.wk_Idx`
 ```
 Why is this usage wrong?

With `foreach`, you can't reuse an existing variable as the loop 
variable. It always declares a new one. If you want to reuse an 
existing variable for your loop, you have to use `for`.

Salih Dincer <salihdb hotmail.com> writes:

On Wednesday, 1 March 2023 at 19:05:10 UTC, DLearner wrote:

 ```
 Error: variable `wk_Idx` is shadowing variable 
 `for3.main.wk_Idx`
 ```
 Why is this usage wrong?

Or use the `each` template which is almost the same as `foreach` 
to avoid the shadowing variable issue.

```d
import std.algorithm, std.range, std.stdio;

enum len = 10;
void main()
{
   int[len] IntArr, i, n;
   len.iota.each!((i, n) => IntArr[i] = n);

   IntArr.writeln; // [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
   assert(IntArr == len.iota.array);
}
```
SDB 79