string to big Int in Go?

Question

Is there a way to convert a string (which is essentially a huge number) from string to Big int in Go?

I tried to first convert it into bytes array

array :

Answer 1

See Example for string to big int conversion.

package main


import (
    "fmt"
    "log"
    "math/big"
)

func main() {
    i := new(big.Int)
    _, err := fmt.Sscan("18446744073709551617", i)
    if err != nil {
        log.Println("error scanning value:", err)
    } else {
        fmt.Println(i)
    }
}

Output:

18446744073709551617

Answer 2

Package big

import "math/big"

func (*Int) SetString

func (z *Int) SetString(s string, base int) (*Int, bool)

SetString sets z to the value of s, interpreted in the given base, and returns z and a boolean indicating success. The entire string (not just a prefix) must be valid for success. If SetString fails, the value of z is undefined but the returned value is nil.

The base argument must be 0 or a value between 2 and MaxBase. If the base is 0, the string prefix determines the actual conversion base. A prefix of “0x” or “0X” selects base 16; the “0” prefix selects base 8, and a “0b” or “0B” prefix selects base 2. Otherwise the selected base is 10.

For example,

package main

import (
    "fmt"
    "math/big"
)

func main() {
    n := new(big.Int)
    n, ok := n.SetString("314159265358979323846264338327950288419716939937510582097494459", 10)
    if !ok {
        fmt.Println("SetString: error")
        return
    }
    fmt.Println(n)
}

Playground: https://play.golang.org/p/ZaSOQoqZB_

Output:

314159265358979323846264338327950288419716939937510582097494459