Re: Happy 2006

[Roy Johnson]

An arguably cleverer way to write the nested loop without using some kind of module:

use strict;
use warnings;

my $year = @ARGV ? shift : 2006;
my $ops = '{-,+,x,/,}';
my $globpat = '{-,}' . (join $ops, (reverse 1..9));

print $globpat, "\n";
for (glob $globpat) {
  tr/x/*/;
  print "$_ == $year\n" if $year == eval;
}

[Perl Mouse]

I'm not a big fan of the glob trick - there's always the possibility something matches (although for the given pattern, that's pretty unlikely). But just for kicks, I compared your solution with mine:

$ /usr/bin/time ./perlmouse ; /usr/bin/time ./ray_johnson 
-9 + 8 * 7 + 654 * 3 - 2 - 1 == 2006
 9 + 8 * 7 + 654 * 3 - 21 == 2006
 9 + 8 * 7 * 6 * 5 - 4 + 321 == 2006
 9 * 8 - 7 + 654 * 3 - 21 == 2006
56.60user 0.19system 2:04.01elapsed 39%CPU (0avgtext+0avgdata 0maxresi
+dent)k
0inputs+0outputs (356major+87minor)pagefaults 0swaps
-9+8*7+654*3-2-1 == 2006
9+8*7+654*3-21 == 2006
9+8*7*6*5-4+321 == 2006
9*8-7+654*3-21 == 2006
56.98user 3.45system 2:43.21elapsed 41%CPU (0avgtext+0avgdata 0maxresi
+dent)k
0inputs+0outputs (398major+21556minor)pagefaults 0swaps

The running time is about the same, but your solution uses a lot more memory, as it makes a list of all possible expressions to test before making the first test, while my solution tests each expressions right after it is constructed. My solution has a lot less pagefaults.

[QM]

The running time is about the same, but your solution uses a lot more memory, as it makes a list of all possible expressions to test before making the first test, while my solution tests each expressions right after it is constructed. My solution has a lot less pagefaults.

Ah, someday soon, glob will be an iterator in scalar context.

[ysth]

It is, but that doesn't help here.

[Perl Mouse]

As pointed out, glob is an iterator in scalar context. However, for provides list context.