http://www.perlmonks.org?node_id=483702


in reply to dynamic map "quadrant" indexing

Here's an iterative solution, similar in spirit to the algorithm discussed in HOP, flip, and swap:

use strict; use warnings; my $base = 4; my $lvl = shift || 2; my @indices = indices( $lvl ); print "$_\n" for @indices; sub indices { my $lvl = shift; die if $lvl < 0; my $first = 'A1'; my @index = map $first, 1..$lvl; my @ret; my $n = 1; { push @ret, join '', @index; my $p = $n; my $j = $#index; $index[ $j--] = $first, $p /= $base until $p % $base; last if $j < 0; $index[ $j ] = chr( ord( $index[ $j ] ) + 1 ) . substr( $index[ $j ], 1 ); ++$n; redo; } return @ret; }

But it's much easier to do this with globs:

my $glob_string = ( '{' . join( ',', 'A'..'D' ) . '}1' ) x $level; my @indices; while ( < $glob_string > ) { push @indices, $_ }

the lowliest monk