why pow(256, 27) gives 0, instead of 105312291668557186697918027683670432318895095400549111254310977536L

On Wednesday, 21 March 2018 at 15:56:00 UTC, aerto wrote:
> why pow(256, 27) gives 0, instead of 105312291668557186697918027683670432318895095400549111254310977536L

that result is simply too big to fit in the result. Try using a bigint instead:

import std.bigint, std.stdio;

void main() {
	BigInt i = 256;
	i ^^= 27;
	writeln(i);
}

On Wed, Mar 21, 2018 at 03:56:00PM +0000, aerto via Digitalmars-d wrote:
> why pow(256, 27) gives 0, instead of 105312291668557186697918027683670432318895095400549111254310977536L

Because 256, being an int type, can only hold a 32-bit result, the maximum of which is 2^31 (or 2^32 if you use uint). But 256^27 = 2^216, far bigger than a 32-bit int can hold.

As Adam said, you probably want to use BigInt instead:

	import std.bigint;
	auto result = pow(BigInt(256), 27);


T

-- 
Food and laptops don't mix.

On Wednesday, 21 March 2018 at 16:00:56 UTC, Adam D. Ruppe wrote:
> On Wednesday, 21 March 2018 at 15:56:00 UTC, aerto wrote:
>> why pow(256, 27) gives 0, instead of 105312291668557186697918027683670432318895095400549111254310977536L
>
> that result is simply too big to fit in the result. Try using a bigint instead:
>
> import std.bigint, std.stdio;
>
> void main() {
> 	BigInt i = 256;
> 	i ^^= 27;
> 	writeln(i);
> }

thanks, a last question in a diffrent function i use writeln(105312291668557186697918027683670432318895095400549111254310977536L); and i get Error: integer overflow any solution >?

On Wednesday, 21 March 2018 at 16:29:26 UTC, aerto wrote:
> thanks, a last question in a diffrent function i use

use

BigInt i = "105312291668557186697918027683670432318895095400549111254310977536";

and it should work. Note the quotation marks - it reads it as a string because a long number literal is limited o 64 bit representations.