Random provides an interface for random values generation, using a pseudo random number generator (PRNG).
Random.rand # => 0.167595 Random.rand(5) # => 2
The above methods delegate to a Random instance.
r = Random.new r.rand # => 0.0372991 r.next_bool # => true r.next_int # => 2223112
This module also defines a global method #rand, which Array#sample and Array#shuffle delegates.
rand # => 0.293829 rand(10) # => 8
An instance of each class that includes Random is a random number generator with its own state. Usually such RNGs can be initialized with a seed, which defines their initial state. It is guaranteed that after initializing two different instances with the same seed, and then executing the same calls on both of them, you will get the same results. This allows exactly reproducing the same seemingly random events by just keeping the seed.
It is possible to make a custom RNG by including Random and implementing #next_u to return an unsigned number of a pre-determined type (usually UInt32). The numbers generated by your RNG must be uniformly distributed in the whole range of possible values for that type (e.g. 0u32..UInt32::MAX). This allows all other methods of Random to be based on this and still produce uniformly distributed results. Your Random class should also have a way to initialize it. For pseudo-random number generators that will usually be an integer seed, but there are no rigid requirements for the initialization.
The default PRNG is Random::PCG32 which has a good overall statistical distribution (low bias of generated numbers) and is fast for overall usages on different platforms, but isn't cryptographically secure. If a third party has access to some generated numbers, she may deduce incoming numbers, putting your application at risk.
It is recommended to use a secure source, such as Random::Secure, Random::ISAAC or ChaCha20 for anything that needs security, such as online games, identification tokens, salts, initializing a PRNG, ... These PRNG are slower but cryptographically secure, so a third party can't deduce incoming numbers.
PCG32.new Initializes an instance with the given seed and sequence.
Initializes an instance seeded from a system source.
See #rand(x).
See #rand.
Generates n random bytes that are encoded into base64.
Generates a hexadecimal string based on n random bytes.
Generates a random Bool.
See #rand.
Same as #rand(Int32::MIN..Int32::MAX).
Generates a random unsigned integer.
Returns a random integer in the given range.
Generates a random integer which is greater than or equal to 0 and less than max.
Generates a random Float64 between 0 and 1.
Returns a random UInt64
Returns a random Int64
Returns a random UInt32
Returns a random Int32
Returns a random UInt16
Returns a random Int16
Returns a random UInt8
Returns a random Int8
Returns a random Float64 which is greater than or equal to 0 and less than max.
Returns a StaticArray filled with random Int64 values.
Returns a StaticArray filled with random UInt32 values.
Returns a StaticArray filled with random Int32 values.
Returns a StaticArray filled with random UInt16 values.
Returns a StaticArray filled with random Int16 values.
Returns a StaticArray filled with random UInt8 values.
Returns a StaticArray filled with random Int8 values.
Returns a random Float in the given range.
Returns a StaticArray filled with random UInt64 values.
Generates a slice filled with n random bytes.
Fills a given slice with random bytes.
URL-safe variant of #base64.
Initializes an instance with the given seed and sequence.
Initializes an instance seeded from a system source.
Generates n random bytes that are encoded into base64.
Check Base64#strict_encode for details.
Random::Secure.base64(4) # => "fK1eYg=="
It is recommended to use the secure Random::Secure as a source or another cryptographically quality PRNG such as Random::ISAAC or ChaCha20.
Generates a hexadecimal string based on n random bytes.
The bytes are encoded into a string of two-digit hexadecimal number (00-ff) per byte.
Random::Secure.hex # => "05f100a1123f6bdbb427698ab664ff5f" Random::Secure.hex(1) # => "1a"
It is recommended to use the secure Random::Secure as a source or another cryptographically quality PRNG such as Random::ISAAC or ChaCha20.
Same as #rand(Int32::MIN..Int32::MAX).
Generates a random unsigned integer.
The integers must be uniformly distributed between 0 and the maximal value for the chosen type.
Returns a random integer in the given range.
The return type always matches the supplied argument.
Random.new.rand(10..20) # => 14 Random.new.rand(Int64::MIN..Int64::MAX) # => -5297435808626736140
Generates a random integer which is greater than or equal to 0 and less than max.
The return type always matches the supplied argument.
Random.new.rand(10) # => 5 Random.new.rand(5000) # => 2243
Generates a random Float64 between 0 and 1.
r = Random.new r.rand # => 0.167595 r.rand # => 0.0372991
Returns a random UInt64
rand(UInt64) # => 15004487597684511003
Returns a random Int64
rand(Int64) # => 4438449217673515190
Returns a random Float64 which is greater than or equal to 0 and less than max.
Random.new.rand(3.5) # => 2.88938 Random.new.rand(10.725) # => 7.70147
Returns a StaticArray filled with random Int64 values.
rand(StaticArray(Int64, 4)) # => StaticArray[4438449217673515190, 8514493061600538358, -4874671083204037318, -7825896160729246667]
Returns a StaticArray filled with random UInt32 values.
rand(StaticArray(UInt32, 4)) # => StaticArray[3147957137, 4245108745, 2207809043, 3184391838]
Returns a StaticArray filled with random Int32 values.
rand(StaticArray(Int32, 4)) # => StaticArray[1870830079, -1043532158, -867180637, -1216773590]
Returns a StaticArray filled with random UInt16 values.
rand(StaticArray(UInt16, 4)) # => StaticArray[39546, 44091, 2874, 17348]
Returns a StaticArray filled with random Int16 values.
rand(StaticArray(Int16, 4)) # => StaticArray[-32554, 32169, -20152, -7686]
Returns a StaticArray filled with random UInt8 values.
rand(StaticArray(UInt8, 4)) # => StaticArray[186, 221, 127, 245]
Returns a StaticArray filled with random Int8 values.
rand(StaticArray(Int8, 4)) # => StaticArray[20, -66, 89, 19]
Returns a random Float in the given range.
Random.new.rand(6.2..21.768) # => 15.2989
Returns a StaticArray filled with random UInt64 values.
rand(StaticArray(UInt64, 4)) # => StaticArray[15004487597684511003, 12027825265648206103, 11303949506191212698, 6228566501671148658]
Generates a slice filled with n random bytes.
Random.new.random_bytes # => [145, 255, 191, 133, 132, 139, 53, 136, 93, 238, 2, 37, 138, 244, 3, 216] Random.new.random_bytes(4) # => [217, 118, 38, 196]
Fills a given slice with random bytes.
slice = Bytes.new(4) # => [0, 0, 0, 0] Random.new.random_bytes(slice) slice # => [217, 118, 38, 196]
URL-safe variant of #base64.
Check Base64#urlsafe_encode for details.
Random::Secure.urlsafe_base64 # => "MAD2bw8QaBdvITCveBNCrw" Random::Secure.urlsafe_base64(8, padding: true) # => "vvP1kcs841I=" Random::Secure.urlsafe_base64(16, padding: true) # => "og2aJrELDZWSdJfVGkxNKw=="
It is recommended to use the secure Random::Secure as a source or another cryptographically quality PRNG such as Random::ISAAC or ChaCha20.
© 2012–2020 Manas Technology Solutions.
Licensed under the Apache License, Version 2.0.
https://crystal-lang.org/api/0.35.1/Random.html