I found this example at Go Cookbook, which is equivalent to rand.Range(min, max int)
(if that function existed):
rand.Intn(max - min) + min
Don't forget to seed the PRNG before calling any rand
function.
rand.Seed(time.Now().UnixNano())
Pergunta
All the integer functions in math/rand
generate non-negative numbers.
rand.Int() int // [0, MaxInt]
rand.Int31() int32 // [0, MaxInt32]
rand.Int31n(n int32) int32 // [0, n)
rand.Int63() int64 // [0, MaxInt64]
rand.Int63n(n int64) int64 // [0, n)
rand.Intn(n int) int // [0, n)
I would like to generate random numbers in the range [-m, n). In other words, I would like to generate a mix of positive and negative numbers.
Solução
I found this example at Go Cookbook, which is equivalent to rand.Range(min, max int)
(if that function existed):
rand.Intn(max - min) + min
Don't forget to seed the PRNG before calling any rand
function.
rand.Seed(time.Now().UnixNano())
Outras dicas
This will generate random numbers within given range [a, b]
rand.Seed(time.Now().UnixNano())
n := a + rand.Intn(b-a+1)
As to prevent repeating min
and max
over and over again, I suggest to switch range and random in thinking about it. This is what I found to work as expected:
package main
import (
"fmt"
"math/rand"
)
// range specification, note that min <= max
type IntRange struct {
min, max int
}
// get next random value within the interval including min and max
func (ir *IntRange) NextRandom(r* rand.Rand) int {
return r.Intn(ir.max - ir.min +1) + ir.min
}
func main() {
r := rand.New(rand.NewSource(55))
ir := IntRange{-1,1}
for i := 0; i<10; i++ {
fmt.Println(ir.NextRandom(r))
}
}
The solution you found in the Cookbook misses to exactly specify how min
and max
work, but of course it meets your specification ([-min, max)). I decided to specify the range as a closed interval ([-min, max], that means its borders are included in the valid range). Compared to my understanding of the Cookbook description:
gives you that random number within any two positive numbers that you specify (in this case, 1 and 6).
(which can be found below the code snippet in the Golang Cookbook)
the Cookbook implementation is off by one (which of course brings it in good company with lots of programs that are helpful at first glance).
A small utility I wrote for generating random slices(very much like python range)
Code - https://github.com/alok87/goutils/blob/master/pkg/random/random.go
import "github.com/alok87/goutils/pkg/random"
random.RangeInt(2, 100, 5)
[3, 10, 30, 56, 67]
Solution that worked for me is:
j = rand.Intn(600) - 100
where m is 100 and n is 500, it will generate numbers from -100 to 499.
This worked for me (Generate random number between 1 and 10)...
import "math/rand"
rand.Seed(time.Now().UnixNano())
randId := rand.Intn(10-1) + 1