queens templates
  n is $;
  addColumn templates
    prev is $;
    addIfPossible templates
      row is $;
      minor is $ - $prev::length - 1;
      major is $ + $prev::length + 1;
      -- If prev is not an array that contains row, send it on...
      $prev -> if <~|[<|=$row>]>
            -> if <|?($(.. as i; -> $ - $i) matches <~|[<|=$minor>]>)>
            -> if <|?($(.. as i; -> $ + $i) matches <~|[<|=$major>]>)>
            -> [ $..., $row] !
    end addIfPossible
    1..$n -> addIfPossible !
  end addColumn
  1..$n -> [$] -> # !
  when <|[](=$n)> do $ !
  otherwise $ -> addColumn -> # !
end queens

solutions is [ 8 -> queens ];
'For 8 queens there are $solutions::length; solutions
' !

columns is ['abcdefgh'...];
'One of them is $solutions(1) -> $(.. as i; -> '$columns($i);$;');
' !

'For 3 queens there are $:[3 -> queens] -> $::length; solutions
' !