rand

rand

https://pkg.go.dev/math/rand@go1.20.1

Package rand implements pseudo-random number generators unsuitable 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.

Example

Example

常量

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变量

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函数

func ExpFloat64

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func ExpFloat64() float64

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

func Float32

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func Float32() float32

Float32 returns, as a float32, a pseudo-random number in the half-open interval [0.0,1.0) from the default Source.

func Float64

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func Float64() float64

Float64 returns, as a float64, a pseudo-random number in the half-open interval [0.0,1.0) from the default Source.

func Int

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func Int() int

Int returns a non-negative pseudo-random int from the default Source.

func Int31

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func Int31() int32

Int31 returns a non-negative pseudo-random 31-bit integer as an int32 from the default Source.

func Int31n

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func Int31n(n int32) int32

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.

func Int63

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func Int63() int64

Int63 returns a non-negative pseudo-random 63-bit integer as an int64 from the default Source.

func Int63n

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func Int63n(n int64) int64

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.

func Intn

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func Intn(n int) int

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.

Example

func NormFloat64

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func NormFloat64() float64

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

func Perm

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func Perm(n int) []int

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.

Example

Example

Example

func Shuffle <- go1.10

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func Shuffle(n int, swap func(i, j int))

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.

Example

Example

func Uint32

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func Uint32() uint32

Uint32 returns a pseudo-random 32-bit value as a uint32 from the default Source.

func Uint64 <- go1.8

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func Uint64() uint64

Uint64 returns a pseudo-random 64-bit value as a uint64 from the default Source.

类型

type Rand

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type Rand struct {
	// contains filtered or unexported fields
}

A Rand is a source of random numbers.

func New

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func New(src Source) *Rand

New returns a new Rand that uses random values from src to generate other random values.

(*Rand) ExpFloat64

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func (r *Rand) ExpFloat64() float64

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

(*Rand) Float32

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func (r *Rand) Float32() float32

Float32 returns, as a float32, a pseudo-random number in the half-open interval [0.0,1.0).

(*Rand) Float64

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func (r *Rand) Float64() float64

Float64 returns, as a float64, a pseudo-random number in the half-open interval [0.0,1.0).

(*Rand) Int

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func (r *Rand) Int() int

Int returns a non-negative pseudo-random int.

(*Rand) Int31

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func (r *Rand) Int31() int32

Int31 returns a non-negative pseudo-random 31-bit integer as an int32.

(*Rand) Int31n

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func (r *Rand) Int31n(n int32) int32

Int31n returns, as an int32, a non-negative pseudo-random number in the half-open interval [0,n). It panics if n <= 0.

(*Rand) Int63

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func (r *Rand) Int63() int64

Int63 returns a non-negative pseudo-random 63-bit integer as an int64.

(*Rand) Int63n

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func (r *Rand) Int63n(n int64) int64

Int63n returns, as an int64, a non-negative pseudo-random number in the half-open interval [0,n). It panics if n <= 0.

(*Rand) Intn

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func (r *Rand) Intn(n int) int

Intn returns, as an int, a non-negative pseudo-random number in the half-open interval [0,n). It panics if n <= 0.

(*Rand) NormFloat64

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func (r *Rand) NormFloat64() float64

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

(*Rand) Perm

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func (r *Rand) Perm(n int) []int

Perm returns, as a slice of n ints, a pseudo-random permutation of the integers in the half-open interval [0,n).

(*Rand) Read <- go1.6

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func (r *Rand) Read(p []byte) (n int, err error)

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.

(*Rand) Seed

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func (r *Rand) Seed(seed int64)

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.

(*Rand) Shuffle <- go1.10

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func (r *Rand) Shuffle(n int, swap func(i, j int))

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.

(*Rand) Uint32

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func (r *Rand) Uint32() uint32

Uint32 returns a pseudo-random 32-bit value as a uint32.

(*Rand) Uint64 <- go1.8

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func (r *Rand) Uint64() uint64

Uint64 returns a pseudo-random 64-bit value as a uint64.

type Source

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type Source interface {
	Int63() int64
	Seed(seed int64)
}

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.

func NewSource

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func NewSource(seed int64) Source

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.

type Source64 <- go1.8

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type Source64 interface {
	Source
	Uint64() uint64
}

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.

type Zipf

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type Zipf struct {
	// contains filtered or unexported fields
}

A Zipf generates Zipf distributed variates.

func NewZipf

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func NewZipf(r *Rand, s float64, v float64, imax uint64) *Zipf

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.

(*Zipf) Uint64

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func (z *Zipf) Uint64() uint64

Uint64 returns a value drawn from the Zipf distribution described by the Zipf object.