Performing math operations on very large numbers in Perl

问题

I have a case where some values in a data file have 64 bit wrap around which makes them very large, like, 18446744073709551608.

So I have to perform a subtraction from 2^64. I tried this using the simple

2^64 - 18446744073709551608

But I guess this number is too large and don't get the actual answer 8. What do I need to do to perform this substraction.

回答1:

Check out the bignum pragma:

use bignum;

print 2**64 - 18446744073709551608;

This should properly print 8.

回答2:

Note that bignum is just a layer that makes all constant numbers automatically Math::BigFloat or Math::BigInt objects. If you only want this for some numbers, you can either specify the use bignum; in a restricted scope, add no bignum; in places, or explicitly use Math::BigFloat->new('your constant') (or BigInt) to make particular numbers and the results of any operations involving them big.

回答3:

use bignum ;

print 2**64 - 18446744073709551608 ,"\n" ;

in perl language , ^ = ** , mod = % good luck !

来源：https://stackoverflow.com/questions/4620054/performing-math-operations-on-very-large-numbers-in-perl