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747_677_634_789_376
On the 8E00000000 day of Advent my True Language gave to me.... a
really big number.
Math::BigInt has been featured in a previous calendar, soon after it had been
moved into the core distribution. However an overlooked addition of the perl
5.8.0 release was today's feature, the bignum pragma. But
first, let's bring everyone up to speed: Math::Big* is set of modules that all
share the purpose of providing large arbitrary/fixed precision/accuracy math.
Basically, when using them you don't have to worry about overflows or rounding
errors.
The joy that is bignum means that through the magic of overloading *every*
number becomes a Big number and consequently everything just DWIMs swimmingly.
There are a few caveats of course, in particular the POD mentions that
typically "short" values like loop counters incurring performance penalties
from their new-found largesse. A more subtle issue is demonstrated in the code
listing, Big numbers don't play well with printf. Despite this, I've used
bignum combined with
Math::Matrix
for higher precision math than is available in
PDL, albeit more slowly and without access
to a lot of other whiz-bang features, but I digress.
There are two final points I'd like to leave you with concerning bignum:
- The
pragma ought to work
wherever the underlying modules will, I can use v.11 from perl 5.8.0 with perl
5.6.0 no problem. And the source says: require 5.005;
- Big means "lots of bits" and not necessarily "Microsoft's advertising
budget". Avagadro's number is Big but so is Planck's constant.
Enjoy!
1 use bignum;
2 use Interpolation commify=>commify;
3
4 print "Straight up\n";
5 print 4**4000, "\n";
6 #=Lotsa numbers
7
8 print "\nNow slightly more legible\n";
9 {
10 $_ = $commify{4**4000};
11 y/,/_/;
12 print $_, "\n";
13 #=Inf
14 }
15
16 #Doh!
17 {
18 print "\nNow slightly more legible\n";
19 $_ = 4**4000;
20
21 #Body of Interpolation::commify
22 1 while s/^(-?\d+)(\d{3})/$1,$2/;
23
24 y/,/_/;
25 print $_, "\n";
26 #=The beginning of this page
27 }