random.go

package main

import (
	"fmt"
	"math/rand"
	"time"
)

// Go’s math/rand package provides pseudorandom number generation.

// Random function to illustrate pseudorandom number generation.
func Random() {

	// For example, rand.Intn returns a random int n, 0 <= n < 100.
	fmt.Print(rand.Intn(100), ",")
	fmt.Print(rand.Intn(100))
	fmt.Println()

	// rand.Float64 returns a float64 f, 0.0 <= f < 1.0.
	fmt.Println(rand.Float64())

	// This can be used to generate random floats in other ranges,
	// for example 5.0 <= f' < 10.0.
	fmt.Print((rand.Float64()*5)+5, ",")
	fmt.Print((rand.Float64() * 5) + 5)
	fmt.Println()

	/*
		The default number generator is deterministic,
		so it’ll produce the same sequence of numbers each time by default.
		To produce varying sequences,
		give it a seed that changes. Note that this is not safe to
		use for random numbers you intend to be secret,
		use crypto/rand for those.
	*/
	s1 := rand.NewSource(time.Now().UnixNano())
	r1 := rand.New(s1)

	// Call the resulting rand.Rand just like the functions on the rand package.
	fmt.Print(r1.Intn(100), ",")
	fmt.Print(r1.Intn(100))
	fmt.Println()

	// If you seed a source with the same number,
	// it produces the same sequence of random numbers.
	s2 := rand.NewSource(42)
	r2 := rand.New(s2)
	fmt.Print(r2.Intn(100), ",")
	fmt.Print(r2.Intn(100))
	fmt.Println()
	s3 := rand.NewSource(42)
	r3 := rand.New(s3)
	fmt.Print(r3.Intn(100), ",")
	fmt.Print(r3.Intn(100))
	fmt.Println()

	// See the math/rand package
	// docs for references on other random quantities that Go can provide.
	// https://golang.org/pkg/math/rand/
}