Documentation
¶
Overview ¶
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.
Index ¶
- func ExpFloat64() float64
- func Float32() float32
- func Float64() float64
- func Int() int
- func Int31() int32
- func Int31n(n int32) int32
- func Int63() int64
- func Int63n(n int64) int64
- func Intn(n int) int
- func NormFloat64() float64
- func Perm(n int) []int
- func Read(p []byte) (n int, err error)deprecated
- func Seed(seed int64)deprecated
- func Shuffle(n int, swap func(i, j int))
- func Uint32() uint32
- func Uint64() uint64
- type Rand
- func (r *Rand) ExpFloat64() float64
- func (r *Rand) Float32() float32
- func (r *Rand) Float64() float64
- func (r *Rand) Int() int
- func (r *Rand) Int31() int32
- func (r *Rand) Int31n(n int32) int32
- func (r *Rand) Int63() int64
- func (r *Rand) Int63n(n int64) int64
- func (r *Rand) Intn(n int) int
- func (r *Rand) NormFloat64() float64
- func (r *Rand) Perm(n int) []int
- func (r *Rand) Read(p []byte) (n int, err error)
- func (r *Rand) Seed(seed int64)
- func (r *Rand) Shuffle(n int, swap func(i, j int))
- func (r *Rand) Uint32() uint32
- func (r *Rand) Uint64() uint64
- type Source
- type Source64
- type Zipf
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
func ExpFloat64 ¶
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 ¶
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 ¶
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 Int31 ¶
func Int31() int32
Int31 returns a non-negative pseudo-random 31-bit integer as an int32 from the default Source.
func Int31n ¶
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 ¶
func Int63() int64
Int63 returns a non-negative pseudo-random 63-bit integer as an int64 from the default Source.
func Int63n ¶
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 ¶
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.
func NormFloat64 ¶
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 ¶
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.
func Read
deprecated
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.
func Seed
deprecated
func Seed(seed int64)
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.
func Shuffle ¶
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.
Types ¶
type Rand ¶
type Rand struct {
// contains filtered or unexported fields
}
A Rand is a source of random numbers.
func (*Rand) ExpFloat64 ¶
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
func (*Rand) Float32 ¶
Float32 returns, as a float32, a pseudo-random number in the half-open interval [0.0,1.0).
func (*Rand) Float64 ¶
Float64 returns, as a float64, a pseudo-random number in the half-open interval [0.0,1.0).
func (*Rand) Int31n ¶
Int31n returns, as an int32, a non-negative pseudo-random number in the half-open interval [0,n). It panics if n <= 0.
func (*Rand) Int63n ¶
Int63n returns, as an int64, a non-negative pseudo-random number in the half-open interval [0,n). It panics if n <= 0.
func (*Rand) Intn ¶
Intn returns, as an int, a non-negative pseudo-random number in the half-open interval [0,n). It panics if n <= 0.
func (*Rand) NormFloat64 ¶
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
func (*Rand) Perm ¶
Perm returns, as a slice of n ints, a pseudo-random permutation of the integers in the half-open interval [0,n).
func (*Rand) Read ¶
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.
func (*Rand) Seed ¶
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.
func (*Rand) Shuffle ¶
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.
type Source ¶
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.
type Source64 ¶
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 ¶
type Zipf struct {
// contains filtered or unexported fields
}
A Zipf generates Zipf distributed variates.
Source Files