in reply to Re^2: Incrementing a large number without Math::BigInt
in thread Incrementing a large number without Math::BigInt

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use strict;
use warnings;

my $i = 100000000;

my $num = '9' x $i;
$num++;
print length ($num) . ' ' . substr $num, 0, 10;

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Prints:

100000001 1000000000

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and executes in about 1 second.

DWIM is Perl's answer to Gödel

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Re^4: Incrementing a large number without Math::BigInt
by Cap'n Steve (Friar) on Apr 26, 2006 at 03:44 UTC
    Wow, that is impressive. Silly me, not even trying the obvious way because I thought Perl couldn't handle it. I've learned my lesson.

    Just curious, what other numerical operations can Perl handle as a string that it can't handle as a number? Deincrementing doesn't seem to work.
[reply]

      Only auto-increment (++) is magical in that fashion and only when the variable is a "string". From perlop:

      The auto-increment operator has a little extra builtin magic to it. If you increment a variable that is numeric, or that has ever been used in a numeric context, you get a normal increment. If, however, the variable has been used in only string contexts since it was set, and has a value that is not the empty string and matches the pattern /^a-zA-Z*0-9*\z/, the increment is done as a string, preserving each character within its range, with carry: 
          print ++($foo = '99');      # prints '100'
    print ++($foo = 'a0');      # prints 'a1'
    print ++($foo = 'Az');      # prints 'Ba'
    print ++($foo = 'zz');      # prints 'aaa'

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      The auto-decrement operator is not magical.
      DWIM is Perl's answer to Gödel
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        |, &, ^ and ~ also work on strings. 

        >perl -e "print 'A'|'B'
C
>perl -e "print 'C'&'E'
A
>perl -e "print 'A'^' '
a

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        I wish << and >> did as well.

        Documented in perlop

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