Re^4: Largest integer in 64-bit perl

[ikegami]

You'll have the same problems using doubles near 2**53 in another language. You'd have to use 64-bit ints to avoid that. Same in Perl. It doesn't hold.

[BillKSmith]

Here is a few examples of the same expression in strawberry perl 5.38.2 and in the gfortran packaged with it. I believe the fortran.

use strict;
use warnings;
use integer;
use feature 'say';

my $base = 3;
my $power = 33;
my $result = $base ** $power;
printf "%d\n", $result;
$power = 38;
$result = $base ** $power;
printf "%d\n", $result

program fort
      integer*8 base, power
      integer*8 result
      base = 3
      power = 33 
      result = base ** power +1;
      print *, result
      power = 38 
      result = base ** power +1;
      print *, result
end program

RESULTS

C:\Users\Bill\forums\monks>perl power3.pl
5559060566555523
1350851717672992000

C:\Users\Bill\forums\monks>gfortran -o power3 power3.f90

C:\Users\Bill\forums\monks>power3.exe
     5559060566555524
  1350851717672992090

[LanX]

The first result is identical, you are adding 1 in Fortran only.

The second one needs 61 bits and is outside float precision in Perl.

Edit

This shows the same result and that the exponentiation is the real "culprit".

  DB<11> $x=1; $x*=3 for 1..38; say $x
1350851717672992089

  DB<12>