Adding really big numbers

[cpaplham]

I'm trying to add one hundred 50-digit numbers together. my code is basically:

 my $big_number = 37107287533902102798797998220837590246510135740250 +
46376937677490009712648124896970078050417018260538 + ...;

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.

[frozenwithjoy]

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

[cpaplham]

I'm using 5.14. I agree, it's strange.

[frozenwithjoy]

Odd. Works fine for me on 5.14.2. What is your operating system?

[salva]

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

[Khen1950fx]

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;
}

[ambrus]

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.