Radix sort

A base-10 radix sort, done on the string representation of the integers. Signs are handled by in-place reversal of the '-' bucket on the last iteration. (The sort in there is not cheating; it only makes sure we process the buckets in the right order, since classify might return the buckets in random order. It might be more efficient to create our own ordered buckets, but this is succinct.)

sub radsort (@ints) {
    my $maxlen = max @ints».chars;
    my @list = @ints».fmt("\%0{$maxlen}d");

    for reverse ^$maxlen -> $r {
        my @buckets = @list.classify( *.substr($r,1) ).sort: *.key;
        @buckets[0].value = @buckets[0].value.reverse.List
            if !$r and @buckets[0].key eq '-';
        @list = flat map *.value.values, @buckets;
    }
    @list».Int;
}

.say for radsort (-2_000 .. 2_000).roll(20);

Output:

-1585
-1427
-1228
-1067
-945
-657
-643
-232
-179
-28
37
411
488
509
716
724
1504
1801
1864
1939