Identity matrix

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:

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:

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