Question

How do you convert a long string of digits (50 digits) into an integer in Go?

I am getting the output for the code below:

number = 2147483647

err = strconv.ParseInt: parsing “37107287533902102798797998220837590246510135740250
“: value out of range

It seems to be able to convert numbers only up to 2147483647.

package main

import "fmt"
import "io/ioutil"
import "strings"
import "strconv"

var (
        number int64
)

func main() {
    fData,err := ioutil.ReadFile("one-hundred_50.txt")
    if err != nil {
            fmt.Println("Err is ",err)
        }   
    strbuffer := string(fData)
    lines := strings.Split(strbuffer, "\n")

    for i, line := range lines {
        fmt.Printf("%d: %s\n", i, line)
        number, err := strconv.Atoi(line)
        fmt.Println("number = ", number)
        fmt.Println("err = ", err)
    }   
}

Answer 1

You want the math/big package, which provides arbitrary-precision integer support.

import "math/big"

func main() {
    // ...
    for i, line := range lines {
        bi := big.NewInt(0)
        if _, ok := bi.SetString(line, 10); ok {
            fmt.Printf("number = %v\n", bi)
        } else {
            fmt.Printf("couldn't interpret line %#v\n", line)
        }
    }
}

Here’s a quick example of it working.