package rand

Import Path
	math/rand (on go.dev)

Dependency Relation
	imports 5 packages, and imported by 3 packages


Involved Source Files

	    exp.go
	    normal.go
	
		Package rand implements pseudo-random number generators suitable for tasks
		such as simulation, but it should not be used for security-sensitive work.
		
		Random numbers are generated by a [Source], usually wrapped in a [Rand].
		Both types should be used by a single goroutine at a time: sharing among
		multiple goroutines requires some kind of synchronization.
		
		Top-level functions, such as [Float64] and [Int],
		are safe for concurrent use by multiple goroutines.
		
		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() {
			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() {
			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 any) {
				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 7, in which 4 are exported)


	/* sort exporteds 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.

			
		
			*Rand : Source
			*Rand : Source64
			*Rand : 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


	
		A Source represents a source of uniformly-distributed
		pseudo-random int64 values in the range [0, 1<<63).
		
		A Source is not safe for concurrent use by multiple goroutines.

		
			( Source) Int63() int64
			( Source) 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.

		
			( Source64) Int63() int64
			( Source64) Seed(seed int64)
			( Source64) Uint64() uint64
		
			*Rand
			
		
			 Source64 : 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 25, in which 19 are exported)


	
		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.
		The returned Source implements Source64.


	
		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.
		
		Deprecated: For almost all use cases, crypto/rand.Read is more appropriate.


	
		Seed uses the provided seed value to initialize the default Source to a
		deterministic state. 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.
		
		If Seed is not called, the generator is seeded randomly at program startup.
		
		Prior to Go 1.20, the generator was seeded like Seed(1) at program startup.
		To force the old behavior, call Seed(1) at program startup.
		Alternately, set GODEBUG=randautoseed=0 in the environment
		before making any calls to functions in this package.
		
		Deprecated: As of Go 1.20 there is no reason to call Seed with
		a random value. Programs that call Seed with a known value to get
		a specific sequence of results should use New(NewSource(seed)) to
		obtain a local random generator.


	
		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.


	


Package-Level Variables (total 9, none are exported)

	


Package-Level Constants (total 7, none are exported)