How to output number in the range 64 bits to 128 bits ( like 2^64, 3^64, 4^64 etc)?

Question

When i was coding i got a problem like: i need to output number which is 2^64 (also 3^64 and others). I have tried unsigned long long int, but it's still not enough (it contains 2^64-1). If anyone know how i can output numbers from 64bits to 128bits, just let me know (btw this task i'm trying to do on C).

That could be an XY-problem. Do you have a problem statement and your proposed solution? — Eugene Sh., Sep 15 '21 at 17:51
c++ has `__int128` but for c you might have to write your own custom logic — Rishabh Deep Singh, Sep 15 '21 at 17:52
@RishabhDeepSingh `__int128` is a gcc extension and works in c or c++ — Alan Birtles, Sep 15 '21 at 17:53
4^64 is outside 128-bit integer range. `2^64, 4^64` are available as `double`. What is the real problem? — chux - Reinstate Monica, Sep 15 '21 at 17:53
@AlanBirtles didn't knew it works on c as well. But it doesn't has output operator so you might to define it yourself. something like https://stackoverflow.com/questions/25114597/how-to-print-int128-in-g — Rishabh Deep Singh, Sep 15 '21 at 17:55
A list of arbitrary precision libraries can be found here: https://en.wikipedia.org/wiki/List_of_arbitrary-precision_arithmetic_software — mevets, Sep 15 '21 at 18:05
https://en.wikipedia.org/wiki/GNU_Multiple_Precision_Arithmetic_Library — 0___________, Sep 15 '21 at 18:06
2^64=10000...(64 0s) in binary. From there it's just a matter of converting to decimal while storing it as a string. Same for 3^64, 4^64 etc, but instead of binary use base 3, base 4 etc — DarkAtom, Sep 15 '21 at 18:10
Please provide enough code so others can better understand or reproduce the problem. — Community, Sep 22 '21 at 10:09

score 1 · Answer 1 · answered Sep 15 '21 at 18:06

First, compile this program:

#include <stdint.h>
int main(void)
{
    return (int128_t) 0;
}

If the compiler prints an error message about the identifier int128_t, then your compiler probably does not support integers wider than 64 bits, regardless of what the type name is.

In that case, you have at least three choices:

If you do not need exact results, you can use double or long double floating-point, as in printf("%g\n", pow(2, 64));.
You can write your own code to implement 128-bit arithmetic from smaller types. For short, simple programs, you can use the same techniques taught in elementary school for multiplying and adding numbers digit by digit, just using a type like uint32_t as a “digit” instead of a single decimal digit. Or you can implement them using single decimal digits, if you prefer. (For example, two uint32_t numbers can be converted to uint64_t and multiplied to make a 64-bit product which you then split into one uint32_t digit to be kept in the current position and one uint32_t digit to be carried to the next position.)
Use an arbitrary-precision library, such as the GNU Multiple Precision Arithmetic Library. This will require downloading and configuring additional software.

How to output number in the range 64 bits to 128 bits ( like 2^64, 3^64, 4^64 etc)?

1 Answers1