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

I'd like it to go as fast as possible and not restrict myself to a certain size, if possible. Doing some tests on my 400mhz laptop, it takes about 5 minutes to create a number with 10 million digits. I haven't tried incrementing it at all. 
use Math::BigInt;

my $i = 10000000;

while (1) {
    my $num = Math::BigInt->new('1' . '0' x $i);
    print $i . "\n";
    $i++;
}

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Update: As a side note, Math::BigInt has some really weird memory usage. It jumps around like crazy, but my first test used about 50 megabytes on average while the second uses about 160.

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Re^3: Incrementing a large number without Math::BigInt
by GrandFather (Saint) on Apr 26, 2006 at 03:00 UTC

    You may be interested that:

    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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      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.
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        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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