cpaplham has asked for the wisdom of the Perl Monks concerning the following question:

I'm trying to add one hundred 50-digit numbers together. my code is basically: 
 my $big_number = 37107287533902102798797998220837590246510135740250 +
46376937677490009712648124896970078050417018260538 + ...;

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I have tried  use bignum; but this didn't work. Whenever I print the value, I get an empty string. I only need about 15 digits of precision.

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Re: Adding really big numbers
by salva (Canon) on Feb 23, 2013 at 09:33 UTC
    If you need to do that application wide, you can compile a custom perl that uses long doubles to represent floating point numbers.

    x86 long doubles have 80 bits and a resolution of 18 digits. Other architectures as SPARC use 128 bits for long doubles.

    Otherwise, you can use Math::LongDouble or Math::MPFR

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Re: Adding really big numbers
by frozenwithjoy (Priest) on Feb 23, 2013 at 00:15 UTC
    Which version of Perl are you using? It works just fine for me on 5.16.1. Using bigint, I get values for every integer. Using bignum, I get values for every int and decimal (except for trailing zeroes). Without an extra module, anything over 20 digits defaults to scientific notation with 15 digits of precision.

    Update: Here is some info on largest positive/negative integers that can be nadled by different setups w/o using modules: Re: maximum value of a scalar

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      I'm using 5.14. I agree, it's strange.
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        Odd. Works fine for me on 5.14.2. What is your operating system?
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Re: Adding really big numbers
by Khen1950fx (Canon) on Feb 23, 2013 at 01:58 UTC
    What lib are you using? How are you declaring accuracy and precision? Maybe this'll help: 
    #!/usr/bin/perl -l

BEGIN {
    $|  = 1;
    $^W = 1;
}

use strict;
use warnings;
use bignum lib => 'FastCalc';

use Memoize;
memoize('really_big');
really_big();

sub really_big {
    bignum->accuracy(15);
    bignum->precision(15);
    
    my $big_number = 3710728753390210279879799822083759024651013574025
+0
    + 46376937677490009712648124896970078050417018260538;
    print $big_number;
}

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[d/l]
Re: Adding really big numbers
by ambrus (Abbot) on Mar 13, 2013 at 21:34 UTC

    If you only need about 15 digits of precision, you don't need to do anything special. Perl's built in arithmetic will read the numbers as double-precision floats and add them that way, which gives about 15 digits of precision.

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