in reply to Why is the size even bigger after pack?

Devel::Size it telling you how many bytes are taken up by the C structure(s) that are used to represent your Perl variable. The numbers you're getting suggest it takes 24 bytes to represent a scalar containing an integer and 48 bytes to represent a scalar containing a string. I can't say I find that particularly surprising.
  • Comment on Re: Why is the size even bigger after pack?

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Re^2: Why is the size even bigger after pack?
by PerlOnTheWay (Monk) on Nov 03, 2011 at 05:23 UTC

    What's the point of pack if it takes more memory after packing?

[reply]
[d/l]

      What did you think it would do?

      pack turns a list of values into a string according to a specific format. If you want to interact with something else which expects values in a specific format (a system call, a foreign function, a binary protocol), pack is your tool. If you want to use less memory, you need something else.

      Improve your skills with Modern Perl: the free book.

[reply]

      Your example only shows one single case. An SV can hold IV's as well as PV's at the same time and a PV representation of 1 takes less space than that of big numbers. YMMV (even with different versions of perl):

      $ cat test.pl
use v5.12;
use Devel::Size "total_size";
for my $num (1, 1000, 100_000_000) {
    say "Value $num:";
    say total_size ($num);
    say total_size (pack "w*", $num);
    }
for my $num ("1", "1000", "100_000_000") {
    say "Value $num:";
    say total_size ($num);
    say total_size (pack "w*", $num);
    }
$ perl test.pl
Value 1:
64
48
Value 1000:
64
48
Value 100000000:
72
48
Value 1:
48
48
Value 1000:
48
48
Value 100_000_000:
56
48
$

      [download]

      Enjoy, Have FUN! H.Merijn
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