How can I make Perl store integers as numbers instead of strings?

Question

I'm parsing many numbers from a text file into hash entries consisting of a key and corresponding reference to array of values. Using Devel::Peek and Devel::Size I noticed that the string representation of the numbers is stored along in this data structure, which wastes memory. How can I rid the memory of these string representations (in other words, how can I turn a PVIV into an IV)?

Answer 1

First of all, if you're trying to save memory at this level, Perl is probably not the tool for you. Perl wantonly "wastes" memory when it provides a speed benefit.

$ perl -e'
   use feature qw( say );
   use Devel::Size qw( size );

   sub f {
      my $x;
      say size($x);
      $x = "x" x 100;
      say size($x);
   }

   f() for 1..2;
'
24
134
134
134

---

Both 0+$scalar and int($scalar) return a scalar of type SVt_IV or SVt_NV. Either of these will do.

$ perl -e'
   use feature qw( say );
   use Devel::Size qw( size );
   my $x = 1234567890;
   my $y = "1234567890";
   say size($x);
   say size($y);
   say size($0+$y);
   say size(int($y));
'
24
44
24
24

---

It's not possible to downgrade an existing scalar, but you could replace it through "aliasing".

$ perl -e'
   use feature qw( say );
   use experimental qw( refaliasing );
   use Devel::Size qw( size );
   my $x = 1234567890;
   my $y = "1234567890";
   say size($x);
   say size($y);
   \$y = \(0+$y);
   say size($y);
'
24
44
24