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How to Get Int31n Type Random Number in Golang?
  • Last Updated : 26 Mar, 2020

Go language provides inbuilt support for generating random numbers of the specified type with the help of a math/rand package. This package implements pseudo-random number generators. These random numbers are generated by a source and this source produces a deterministic sequence of values every time when the program run. And if you want to random numbers for security-sensitive work, then use the crypto/rand package.
You are allowed to generate a non-negative pseudo-random number in [0, n) of 31-bit integer n as an int32 type from the default source with the help of the Int31n() function provided by the math/rand package. So, you need to add a math/rand package in your program with the help of the import keyword to access the Int31() function. This method will panic if the value of n is <= 0.

Syntax:

func Int31n(n int32) int32

Let us discuss this concept with the help of the given examples:

Example 1:

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// Golang program to illustrate
// how to get a random number
package main
  
import (
    "fmt"
    "math/rand"
)
  
// Main function
func main() {
  
    // Finding random numbers of int31n type
    // Using Int31n() function
    res_1 := rand.Int31n(2)
    res_2 := rand.Int31n(4)
    res_3 := rand.Int31n(1)
  
    // Displaying the result
    fmt.Println("Random Number 1: ", res_1)
    fmt.Println("Random Number 2: ", res_2)
    fmt.Println("Random Number 3: ", res_3)
}

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Output:



Random Number 1:  1
Random Number 2:  3
Random Number 3:  0

Example 2:

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// Golang program to illustrate
// how to get a random number
package main
  
import (
    "fmt"
    "math/rand"
)
  
// Main function
func main() {
  
    // If the value of this function
    // is 0 or less than zero
    // the this method will panics
    res_1 := rand.Int31n(0)
    res_2 := rand.Int31n(-1)
  
    // Displaying the result
    fmt.Println("Random Number 1: ", res_1)
    fmt.Println("Random Number 2: ", res_2)
  
}

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Output:

panic: invalid argument to Int31n

goroutine 1 [running]:
math/rand.(*Rand).Int31n(0x43e280, 0x0, 0x43e280, 0x460000)
/usr/local/go/src/math/rand/rand.go:128 +0x180
math/rand.Int31n(…)
/usr/local/go/src/math/rand/rand.go:324
main.main()
/tmp/sandbox269134149/prog.go:16 +0x40




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