random

Utilities for generating random values in Koto.

At the core of the module is the Rng type, which is a seedable random number generator. Each thread has access to a generator with a randomly selected seed, or unique generators can be created with random.generator.

The xoshiro256++ algorithm is used to generate random values, which is fast and portable, but not cryptographically secure.

bool

|| -> Bool

Generates a random boolean using the current thread's generator.

Example

# Seed the thread Rng so that we get predictable results
random.seed 99

random.bool()
# -> false
random.bool()
# -> true

generator

|| -> Rng

Creates an Rng with a randomly generated seed.

|Number| -> Rng

Creates an Rng with a specified seed.

Example

rng = random.generator 99
rng.pick (1, 2, 3)
# -> 1
rng.bool()
# -> true

number

|| -> Number

Generates a random number using the current thread's generator.

The number will be a floating point value in the range from 0 up to but not including 1.

Example

# Seed the thread Rng so that we get predictable results
random.seed 123

# Print random floats up to 3 decimal places
print '{random.number():.3}'
# -> 0.646
print '{random.number():.3}'
# -> 0.838

pick

|Indexable| -> Any?

Selects a random value from the input using the current thread's generator.

• If the input is empty, then null will be returned.
• If the input is a map, then a tuple containing the key and value of a randomly selected entry will be returned.
• If the input is a range, then the result will be an integer within the given range.
• If the input is some other indexable type (like a list or tuple), then a randomly selected element from the input will be returned.

Example

# Seed the thread Rng so that we get predictable results
random.seed -1

random.pick (123, -1, 99)
# -> -1
random.pick 10..20
# -> 19
random.pick {foo: 42, bar: 99, baz: 123}
# -> ('baz', 123)
random.pick []
# -> null

seed

|Number| -> Null

Seeds the current thread's generator so that it produces predictable results.

Example

from iterator import generate
from random import pick, seed

# Returns a tuple containing three numbers from 1 to 10
pick_3 = || generate((|| pick 1..=10), 3).to_tuple()

seed 1
pick_3()
# -> (9, 8, 2)

seed 2
pick_3()
# -> (8, 6, 7)

seed 1
pick_3()
# -> (9, 8, 2)

shuffle

|Indexable| -> Any

Reorders the entries in a container so that they have a new randomly shuffled order, and returns the container.

from random import seed, shuffle

x = [1, 2, 3, 4, 5]

seed 2
shuffle x
# -> [1, 5, 4, 3, 2]
shuffle x
# -> [3, 1, 4, 2, 5]

y = {a: 1, b: 2, c: 3}
shuffle y
# -> {c: 3, a: 1, b: 2}
shuffle y
# -> {c: 3, b: 2, a: 1}

Rng

Rng is the random module's core random generator.

The xoshiro256++ algorithm is used to generate random values, which is fast and portable, but not cryptographically secure.

Rng.bool

See random.bool.

Rng.number

See random.number.

Rng.pick

See random.pick.

Rng.shuffle

See random.shuffle.

Rng.seed

See random.seed.