CODEWITHSUNDEEP
go
Amol M Kulkarni
Amol M Kulkarni

Reputation: 21629

Parse string to specific type of int (int8, int16, int32, int64)

I am trying to parse a string into an integer in Go. The Problem I found with it is in the documentation its mentioned syntax is as follows:

ParseInt(s string, base int, bitSize int)

where, s is the string to be parsed, base is implied by the string's prefix: base 16 for "0x", base 8 for "0", and base 10 otherwise.

The bitSize parameter is where I am facing problem. As per documentation of ParseInt, it specifies the integer type that the result must fit into. Bit sizes 0, 8, 16, 32, and 64 correspond to int, int8, int16, int32, and int64.

But for all the values like 0, 8, 16, 32, and 64. I am getting same type return value. I.e of int64 type.

Could anyone point me out what am I missing.

Code: https://play.golang.org/p/F3LbUh_maY

Upvotes: 51

Views: 76614

Answers (3)

Zombo
Zombo

Reputation: 1

You can use Sscan:

package main
import "fmt"

func main() {
   {
      var n int8
      fmt.Sscan("100", &n)
      fmt.Println(n == 100)
   }
   {
      var n int16
      fmt.Sscan("100", &n)
      fmt.Println(n == 100)
   }
   {
      var n int32
      fmt.Sscan("100", &n)
      fmt.Println(n == 100)
   }
   {
      var n int64
      fmt.Sscan("100", &n)
      fmt.Println(n == 100)
   }
}

https://golang.org/pkg/fmt#Sscan

Upvotes: 4

Salvador Dali
Salvador Dali

Reputation: 222521

As per documentation

func ParseInt(s string, base int, bitSize int) (i int64, err error)

ParseInt always return int64 no matter what. Moreover

The bitSize argument specifies the integer type that the result must fit into

So basically the your bitSize parameter only tells that the string value that you are going to parse should fit the bitSize after parsing. If not, out of range will happen.

Like in this PlayGround: strconv.ParseInt("192", 10, 8) (as you see the value after the parsing would be bigger than maximum value of int8).

If you want to parse it to whatever value you need, just use int8(i) afterwards (int8, int16, int32).

P.S. because you touched the topic how to convert to specific intX, I would outline that it is also possible to convert to unsigned int.

Upvotes: 55

Paul Hankin
Paul Hankin

Reputation: 58241

ParseInt always returns an int64, and you need to convert the result to your desired type. When you pass 32 as the third argument, then you'll get a parse error if the parsed value won't fit into an int32, but the returned type is always int64.

For example:

i, err := strconv.ParseInt("9207", 10, 32)
if err != nil {
    panic(err)
}
result := int32(i)
fmt.Printf("Parsed int is %d\n", result)

Upvotes: 47

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