How to multiply integers larger than uint64?

Question

#include <iostream>
#include <limits>
int main(void) {
    cout << std::numeric_limits<uint64_t>::max();
    return 0;    
}

The code above outputs (on my machine) 18446744073709551615, but I'm trying to multiply numbers that have at least 25 digits. How to properly handle a multiplication of 2 integers that are larger than uint64?

Red about the [The GNU Multiple Precision Arithmetic Library](https://gmplib.org/). — Some programmer dude, Jan 12 '14 at 07:46
You'll need to use a bignum library, like [GMP](https://gmplib.org/) — Yuushi, Jan 12 '14 at 07:46
Get a bigint library. http://stackoverflow.com/a/8147818/179910 My advice: avoid GMP like the plague. Actually, a quick shot of penicillin can cure the plague, so avoid GMP a lot more. — Jerry Coffin, Jan 12 '14 at 07:47
Related ... http://stackoverflow.com/questions/15319967/exact-decimal-datatype-for-c — Mick, Nov 21 '16 at 07:04

score 3 · Accepted Answer · edited Jun 14 '14 at 14:57

3

You need to use a library that handles big numbers. Here are some of them:

The GNU Multiple Precision Arithmetic Library

https://gmplib.org/
C++ Big Integer Library

https://mattmccutchen.net/bigint/
Boost.Multiprecision

http://www.boost.org/doc/libs/1_55_0/libs/multiprecision/doc/html/index.html

edited Jun 14 '14 at 14:57

Ferruccio

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answered Jan 12 '14 at 08:49

bolov

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How to multiply integers larger than uint64?

1 Answers1