package rand

Import Path
	math/rand (on golang.org and go.dev)

Dependency Relation
	imports 2 packages, and imported by 6 packages

Involved Source Files exp.go normal.go Package rand implements pseudo-random number generators unsuitable for security-sensitive work. Random numbers are generated by a Source. Top-level functions, such as Float64 and Int, use a default shared Source that produces a deterministic sequence of values each time a program is run. Use the Seed function to initialize the default Source if different behavior is required for each run. The default Source is safe for concurrent use by multiple goroutines, but Sources created by NewSource are not. This package's outputs might be easily predictable regardless of how it's seeded. For random numbers suitable for security-sensitive work, see the crypto/rand package. rng.go zipf.go
Code Examples package main import ( "fmt" "math/rand" ) func main() { // Seeding with the same value results in the same random sequence each run. // For different numbers, seed with a different value, such as // time.Now().UnixNano(), which yields a constantly-changing number. rand.Seed(42) answers := []string{ "It is certain", "It is decidedly so", "Without a doubt", "Yes definitely", "You may rely on it", "As I see it yes", "Most likely", "Outlook good", "Yes", "Signs point to yes", "Reply hazy try again", "Ask again later", "Better not tell you now", "Cannot predict now", "Concentrate and ask again", "Don't count on it", "My reply is no", "My sources say no", "Outlook not so good", "Very doubtful", } fmt.Println("Magic 8-Ball says:", answers[rand.Intn(len(answers))]) } package main import ( "fmt" "math/rand" ) func main() { // Seeding with the same value results in the same random sequence each run. // For different numbers, seed with a different value, such as // time.Now().UnixNano(), which yields a constantly-changing number. rand.Seed(86) fmt.Println(rand.Intn(100)) fmt.Println(rand.Intn(100)) fmt.Println(rand.Intn(100)) } package main import ( "fmt" "math/rand" ) func main() { for _, value := range rand.Perm(3) { fmt.Println(value) } } package main import ( "fmt" "math/rand" "strings" ) func main() { words := strings.Fields("ink runs from the corners of my mouth") rand.Shuffle(len(words), func(i, j int) { words[i], words[j] = words[j], words[i] }) fmt.Println(words) } package main import ( "fmt" "math/rand" ) func main() { numbers := []byte("12345") letters := []byte("ABCDE") // Shuffle numbers, swapping corresponding entries in letters at the same time. rand.Shuffle(len(numbers), func(i, j int) { numbers[i], numbers[j] = numbers[j], numbers[i] letters[i], letters[j] = letters[j], letters[i] }) for i := range numbers { fmt.Printf("%c: %c\n", letters[i], numbers[i]) } } package main import ( "fmt" "math/rand" "os" "text/tabwriter" ) func main() { // Create and seed the generator. // Typically a non-fixed seed should be used, such as time.Now().UnixNano(). // Using a fixed seed will produce the same output on every run. r := rand.New(rand.NewSource(99)) // The tabwriter here helps us generate aligned output. w := tabwriter.NewWriter(os.Stdout, 1, 1, 1, ' ', 0) defer w.Flush() show := func(name string, v1, v2, v3 interface{}) { fmt.Fprintf(w, "%s\t%v\t%v\t%v\n", name, v1, v2, v3) } // Float32 and Float64 values are in [0, 1). show("Float32", r.Float32(), r.Float32(), r.Float32()) show("Float64", r.Float64(), r.Float64(), r.Float64()) // ExpFloat64 values have an average of 1 but decay exponentially. show("ExpFloat64", r.ExpFloat64(), r.ExpFloat64(), r.ExpFloat64()) // NormFloat64 values have an average of 0 and a standard deviation of 1. show("NormFloat64", r.NormFloat64(), r.NormFloat64(), r.NormFloat64()) // Int31, Int63, and Uint32 generate values of the given width. // The Int method (not shown) is like either Int31 or Int63 // depending on the size of 'int'. show("Int31", r.Int31(), r.Int31(), r.Int31()) show("Int63", r.Int63(), r.Int63(), r.Int63()) show("Uint32", r.Uint32(), r.Uint32(), r.Uint32()) // Intn, Int31n, and Int63n limit their output to be < n. // They do so more carefully than using r.Int()%n. show("Intn(10)", r.Intn(10), r.Intn(10), r.Intn(10)) show("Int31n(10)", r.Int31n(10), r.Int31n(10), r.Int31n(10)) show("Int63n(10)", r.Int63n(10), r.Int63n(10), r.Int63n(10)) // Perm generates a random permutation of the numbers [0, n). show("Perm", r.Perm(5), r.Perm(5), r.Perm(5)) }
Package-Level Type Names (total 4)
/* sort by: | */
A Rand is a source of random numbers. ExpFloat64 returns an exponentially distributed float64 in the range (0, +math.MaxFloat64] with an exponential distribution whose rate parameter (lambda) is 1 and whose mean is 1/lambda (1). To produce a distribution with a different rate parameter, callers can adjust the output using: sample = ExpFloat64() / desiredRateParameter Float32 returns, as a float32, a pseudo-random number in the half-open interval [0.0,1.0). Float64 returns, as a float64, a pseudo-random number in the half-open interval [0.0,1.0). Int returns a non-negative pseudo-random int. Int31 returns a non-negative pseudo-random 31-bit integer as an int32. Int31n returns, as an int32, a non-negative pseudo-random number in the half-open interval [0,n). It panics if n <= 0. Int63 returns a non-negative pseudo-random 63-bit integer as an int64. Int63n returns, as an int64, a non-negative pseudo-random number in the half-open interval [0,n). It panics if n <= 0. Intn returns, as an int, a non-negative pseudo-random number in the half-open interval [0,n). It panics if n <= 0. NormFloat64 returns a normally distributed float64 in the range -math.MaxFloat64 through +math.MaxFloat64 inclusive, with standard normal distribution (mean = 0, stddev = 1). To produce a different normal distribution, callers can adjust the output using: sample = NormFloat64() * desiredStdDev + desiredMean Perm returns, as a slice of n ints, a pseudo-random permutation of the integers in the half-open interval [0,n). Read generates len(p) random bytes and writes them into p. It always returns len(p) and a nil error. Read should not be called concurrently with any other Rand method. Seed uses the provided seed value to initialize the generator to a deterministic state. Seed should not be called concurrently with any other Rand method. Shuffle pseudo-randomizes the order of elements. n is the number of elements. Shuffle panics if n < 0. swap swaps the elements with indexes i and j. Uint32 returns a pseudo-random 32-bit value as a uint32. Uint64 returns a pseudo-random 64-bit value as a uint64. *T : Source *T : Source64 *T : io.Reader func New(src Source) *Rand func NewZipf(r *Rand, s float64, v float64, imax uint64) *Zipf func math/big.(*Int).Rand(rnd *Rand, n *big.Int) *big.Int func testing/quick.Value(t reflect.Type, rand *Rand) (value reflect.Value, ok bool) func testing/quick.Generator.Generate(rand *Rand, size int) reflect.Value
A Source represents a source of uniformly-distributed pseudo-random int64 values in the range [0, 1<<63). ( T) Int63() int64 ( T) Seed(seed int64) *Rand Source64 (interface) func NewSource(seed int64) Source func New(src Source) *Rand
A Source64 is a Source that can also generate uniformly-distributed pseudo-random uint64 values in the range [0, 1<<64) directly. If a Rand r's underlying Source s implements Source64, then r.Uint64 returns the result of one call to s.Uint64 instead of making two calls to s.Int63. ( T) Int63() int64 ( T) Seed(seed int64) ( T) Uint64() uint64 *Rand T : Source
A Zipf generates Zipf distributed variates. Uint64 returns a value drawn from the Zipf distribution described by the Zipf object. func NewZipf(r *Rand, s float64, v float64, imax uint64) *Zipf
Package-Level Functions (total 19)
ExpFloat64 returns an exponentially distributed float64 in the range (0, +math.MaxFloat64] with an exponential distribution whose rate parameter (lambda) is 1 and whose mean is 1/lambda (1) from the default Source. To produce a distribution with a different rate parameter, callers can adjust the output using: sample = ExpFloat64() / desiredRateParameter
Float32 returns, as a float32, a pseudo-random number in the half-open interval [0.0,1.0) from the default Source.
Float64 returns, as a float64, a pseudo-random number in the half-open interval [0.0,1.0) from the default Source.
Int returns a non-negative pseudo-random int from the default Source.
Int31 returns a non-negative pseudo-random 31-bit integer as an int32 from the default Source.
Int31n returns, as an int32, a non-negative pseudo-random number in the half-open interval [0,n) from the default Source. It panics if n <= 0.
Int63 returns a non-negative pseudo-random 63-bit integer as an int64 from the default Source.
Int63n returns, as an int64, a non-negative pseudo-random number in the half-open interval [0,n) from the default Source. It panics if n <= 0.
Intn returns, as an int, a non-negative pseudo-random number in the half-open interval [0,n) from the default Source. It panics if n <= 0.
New returns a new Rand that uses random values from src to generate other random values.
NewSource returns a new pseudo-random Source seeded with the given value. Unlike the default Source used by top-level functions, this source is not safe for concurrent use by multiple goroutines.
NewZipf returns a Zipf variate generator. The generator generates values k ∈ [0, imax] such that P(k) is proportional to (v + k) ** (-s). Requirements: s > 1 and v >= 1.
NormFloat64 returns a normally distributed float64 in the range [-math.MaxFloat64, +math.MaxFloat64] with standard normal distribution (mean = 0, stddev = 1) from the default Source. To produce a different normal distribution, callers can adjust the output using: sample = NormFloat64() * desiredStdDev + desiredMean
Perm returns, as a slice of n ints, a pseudo-random permutation of the integers in the half-open interval [0,n) from the default Source.
Read generates len(p) random bytes from the default Source and writes them into p. It always returns len(p) and a nil error. Read, unlike the Rand.Read method, is safe for concurrent use.
Seed uses the provided seed value to initialize the default Source to a deterministic state. If Seed is not called, the generator behaves as if seeded by Seed(1). Seed values that have the same remainder when divided by 2³¹-1 generate the same pseudo-random sequence. Seed, unlike the Rand.Seed method, is safe for concurrent use.
Shuffle pseudo-randomizes the order of elements using the default Source. n is the number of elements. Shuffle panics if n < 0. swap swaps the elements with indexes i and j.
Uint32 returns a pseudo-random 32-bit value as a uint32 from the default Source.
Uint64 returns a pseudo-random 64-bit value as a uint64 from the default Source.