Re: Happy 2006

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;
}
[download]

Caution: Contents may have been coded under pressure.

Comment on Re: Happy 2006 Download Code

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Re^2: Happy 2006 by Perl Mouse (Chaplain) on Jan 11, 2006 at 01:27 UTC
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+87+6543-2-1 == 2006 9+87+6543-21 == 2006 9+8765-4+321 == 2006 98-7+6543-21 == 2006 56.98user 3.45system 2:43.21elapsed 41%CPU (0avgtext+0avgdata 0maxresi +dent)k 0inputs+0outputs (398major+21556minor)pagefaults 0swaps [download] 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. `Perl --((8:>`	[reply] [d/l]
Re^3: Happy 2006 by QM (Parson) on Jan 17, 2006 at 05:35 UTC
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. -QM -- Quantum Mechanics: The dreams stuff is made of	[reply] [d/l]
Re^4: Happy 2006 by ysth (Canon) on Jan 17, 2006 at 06:17 UTC
It is, but that doesn't help here.	[reply]
Re^5: Happy 2006 by QM (Parson) on Jan 18, 2006 at 03:23 UTC
Re^4: Happy 2006 by Perl Mouse (Chaplain) on Jan 18, 2006 at 10:05 UTC
As pointed out, `glob` is an iterator in scalar context. However, `for` provides list context. `Perl --((8:>*`	[reply]