in reply to Re^3: Largest integer in 64-bit perl
in thread Largest integer in 64-bit perl

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.

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Re^5: Largest integer in 64-bit perl
by BillKSmith (Monsignor) on Jun 02, 2025 at 04:24 UTC
    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

    [download]
    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

    [download]

    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

    [download]
    Bill
[reply]
[d/l]
[select]
      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>

      [download]

      Cheers Rolf
      (addicted to the Perl Programming Language :)
      see Wikisyntax for the Monastery

[reply]
[d/l]

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