go - Calculating large exponentiation in Golang -

i've been trying calculating 2^100 in golang. understand limit of numeric type , tried using math/big package. here's i've tried can't figure out why doesn't work.

i've used computation powers of two method calculate exponentiation.

package main  import (     "fmt"     "math/big" )  func main() {     2 := big.newint(2)     hundred := big.newint(50)     fmt.printf("2 ** 100    %d\n", expbypowoftwo(two, hundred)) }  func expbypowoftwo(base, power *big.int) *big.int {     result := big.newint(1)     0 := big.newint(0)     power != 0 {         if modby2(power) != 0 {             multiply(result, base)         }         power = divideby2(power)         base = multiply(base, base)     }     return result }  func modby2(x *big.int) *big.int {     return big.newint(0).mod(x, big.newint(2)) }  func divideby2(x *big.int) *big.int {     return big.newint(0).div(x, big.newint(2)) }  func multiply(x, y *big.int) *big.int {     return big.newint(0).mul(x, y) } 

bigint package allows calculate x^y in log time (for reason called exp). need pass nil last parameter.

package main  import (     "fmt"     "math/big" )  func main() {     fmt.println(new(big.int).exp(big.newint(5), big.newint(20), nil)) } 

if interested how calculate yourself, take @ implementation:

func powbig(a, n int) *big.int{     tmp := big.newint(int64(a))     res := big.newint(1)     n > 0 {         temp := new(big.int)         if n % 2 == 1 {             temp.mul(res, tmp)             res = temp         }         temp = new(big.int)         temp.mul(tmp, tmp)         tmp = temp         n /= 2     }     return res } 

or play on go playground.