in reply to Style: buried variables or double referencing?

This would be my solution. 
use constant LONG_COUNT => 14;
use constant SHORT_COUNT => 9;

my $some_variable;

# ...

my $loop_count = $some_variable eq 'x' ? LONG_COUNT : SHORT_COUNT;

for $i (0 .. $loop_count) {
   # do some stuff
   print $i;
}

[download]
You might even get rid of loop_count and use (0 .. $some_variable eq 'x' ? LONG_COUNT : SHORT_COUNT) directly.

Now LONG_COUNT and SHORT_COUNT will be easy to find and you can document them at the use constant.

-- gam3
A picture is worth a thousand words, but takes 200K.

Replies are listed 'Best First'.
Re^2: Style: buried variables or double referencing?
by tilly (Archbishop) on Aug 20, 2005 at 18:12 UTC
    TheDamian's Best Practices gives several good reasons why constant should be deprecated in favour of Readonly. In which case you would have: 
    use Readonly;
Readonly my $LONG_COUNT => 14;
Readonly my $SHORT_COUNT => 9;
# ...

    [download]
    I fully agree with his recommend since I never saw that constant buys me anything useful.
[reply]
[d/l]

      Depends. Readonly is slow, and not everyone can use Readonly::XS. The following code takes 48 seconds:

      use Readonly;
Readonly $C1 => 1;

my $t0 = time();
my $a = 2;
for (1 .. 10000000) {
    if ($a ++ == $C1) {
        ;
    }
}
print time() - $t0;

      [download]

      When this takes 4 second:

      use constant C1 => 1;

my $t0 = time();
my $a = 2;
for (1 .. 10000000) {
    if ($a ++ == C1) {
        ;
    }
}
print time() - $t0;

      [download]

      If performance is important, use constant.

[reply]
[d/l]
[select]
        I'd be happier developing with a function that called Readonly in development and then something like this in production: 
        sub fake_readonly {
  $_[0] = $_[1];
}

        [download]
        And now you get most of the advantages of Readonly, but performance is not a problem. (I don't like constant because I'm a big fan of interpolating, and I often have to check whether someone has a constant or function because I'm afraid that it will try to suck up arguments.)
[reply]
[d/l]
        That's a difference of 4.4 microseconds. That's a difference I'm willing to take in most of my programs.
[reply]

      TheDamian's <cite>Best Practices</cite> gives several good reasons why constant should be deprecated in favour of Readonly:

      Readonly my $LONG_COUNT => 14;
Readonly my $SHORT_COUNT => 9;

      [download]

      But Damian also says in his book that you should use hashes for look-up tables, rather than if/else tests. And that's definitely a look-up table.

      So how about something like:

      Readonly \my %THWAPP_COUNT => (
  x => 14,
  y => 9,
);

      [download]

      (Adjective describing what sort of a count this is courtesy of Acme::MetaSyntactic::batman.)

      Smylers

[reply]
[d/l]
[select]

In Section Seekers of Perl Wisdom