Magic squares/Perl 6

From Rosetta Code

Rather than having multiple examples for different orders of magic square, this will generate a magic square for any valid n x n grid.

Invoke at the command line and pass in the desired size as a parameter.

Works with: Rakudo version 2016-02
See:
sub MAIN (Int $n where {$n > 0}) {
 
my @sq;
my $i = 1;
my $h = $n div 2;
my $q = $n div 4;
 
gen-sq($n);
 
say .fmt("%{$i.chars}d", ' ') for @sq;
 
say "\nThe magic number is ", [+] @sq[0].list;
 
 
multi sub gen-sq (2) { # invalid
note "Sorry, can not generate a 2 x 2 magic square." and exit;
}
 
multi sub gen-sq ($n where {$n % 2}) { # odd
my $x = $n/2;
my $y = 0;
@sq[($i % $n ?? $y-- !! $y++) % $n][($i % $n ?? $x++ !! $x) % $n] = $i++ for ^$n²;
}
 
multi sub gen-sq ($n where {$n %% 4}) { # doubly even
my $x = 0;
my $y = 0;
@sq[$i % $n ?? $y !! $y++][($i-1) % $n] = $i++ for ^$n²;
for ^$q -> $r {
for $q ..^ $n - $q -> $c {
my= $n - 1 - $r;
my= $n - 1 - $c;
(@sq[$r;$c], @sq[;]) = (@sq[;], @sq[$r;$c]);
(@sq[$c;$r], @sq[;]) = (@sq[;], @sq[$c;$r]);
}
}
}
 
multi sub gen-sq ($n where {$n %% 2 and $n % 4}) { # singly even
gen-sq($h);
$i *= 4;
for ^$h -> $r {
for ^$h -> $c {
@sq[$r + $h; $c] = @sq[$r;$c] + $h² * 3;
@sq[$r; $c + $h] = @sq[$r;$c] + $h² * 2;
@sq[$r + $h; $c + $h] = @sq[$r;$c] + $h²;
}
for ^$q -> $c {
next if $c == 0 and $r == ($h-1) div 2;
(@sq[$r;$c], @sq[$r + $h;$c]) = (@sq[$r + $h;$c], @sq[$r;$c]);
}
if $h > 4 {
for ($n - $q + 1) ..^ $n -> $c {
(@sq[$r;$c], @sq[$r + $h;$c]) = (@sq[$r + $h;$c], @sq[$r;$c]);
}
}
}
(@sq[$q;$q], @sq[$q+$h;$q]) = (@sq[$q+$h;$q], @sq[$q;$q]);
}
}