> For the complete documentation index, see [llms.txt](https://trizen.gitbook.io/perl6-rosettacode/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://trizen.gitbook.io/perl6-rosettacode/programming_tasks/i/identity_matrix.md).

# Identity matrix

```perl
sub identity-matrix($n) {
    my @id;
    for flat ^$n X ^$n -> $i, $j {
        @id[$i][$j] = +($i == $j);
    }
    @id;
}

.say for identity-matrix(5);
```

#### Output:

```
[1 0 0 0 0]
[0 1 0 0 0]
[0 0 1 0 0]
[0 0 0 1 0]
[0 0 0 0 1]
```

On the other hand, this may be clearer and/or faster:

```perl
sub identity-matrix($n) {
    my @id = [0 xx $n] xx $n;
    @id[$_][$_] = 1 for ^$n;
    @id;
}
```

Here is yet an other way to do it:

```perl
sub identity-matrix($n) {
    [1, |(0 xx $n-1)], *.rotate(-1) ... *[*-1]
}
```