wren

a classy little scripting language

Random Class

A simple, fast pseudo-random number generator. Internally, it uses the well equidistributed long-period linear PRNG (WELL512a).

Each instance of the class generates a sequence of randomly distributed numbers based on the internal state of the object. The state is initialized from a seed. Two instances with the same seed generate the exact same sequence of numbers.

It must be imported from the random module:

import "random" for Random

Constructors #

Random.new() #

Creates a new generator whose state is seeded based on the current time.

var random = Random.new()

Random.new(seed) #

Creates a new generator initialized with [seed]. The seed can either be a number, or a non-empty sequence of numbers. If the sequnce has more than 16 elements, only the first 16 are used. If it has fewer, the elements are cycled to generate 16 seed values.

Random.new(12345) 
Random.new("appleseed".codePoints)

Methods #

float() #

Returns a floating point value between 0.0 and 1.0, including 0.0, but excluding 1.0.

var random = Random.new(12345) 
System.print(random.float()) 0.53178795980617
System.print(random.float()) 0.20180515043262
System.print(random.float()) 0.43371948658705

float(end) #

Returns a floating point value between 0.0 and end, including 0.0 but excluding end.

var random = Random.new(12345) 
System.print(random.float(0))     0
System.print(random.float(100))   20.180515043262
System.print(random.float(-100))  -43.371948658705

float(start, end) #

Returns a floating point value between start and end, including start but excluding end.

var random = Random.new(12345) 
System.print(random.float(3, 4))    3.5317879598062
System.print(random.float(-10, 10)) -5.9638969913476
System.print(random.float(-4, 2))   -1.3976830804777

int(end) #

Returns an integer between 0 and end, including 0 but excluding end.

var random = Random.new(12345) 
System.print(random.int(1))    0
System.print(random.int(10))   2
System.print(random.int(-50))  -22

int(start, end) #

Returns an integer between start and end, including start but excluding end.

var random = Random.new(12345) 
System.print(random.int(3, 4))    3
System.print(random.int(-10, 10)) -6
System.print(random.int(-4, 2))   -2

sample(list) #

Selects a random element from list.

sample(list, count) #

Samples count randomly chosen unique elements from list.

This uses “random without replacement” sampling—no index in the list will be selected more than once.

Returns a new list of the selected elements.

It is an error if count is greater than the number of elements in the list.

shuffle(list) #

Randomly shuffles the elements in list. The items are randomly re-ordered in place.

var random = Random.new(12345) 
var list = (1..5).toList 
random.shuffle(list) 
System.print(list) [3, 2, 4, 1, 5]

Uses the Fisher-Yates algorithm to ensure that all permutations are chosen with equal probability.

Keep in mind that a list with even a modestly large number of elements has an astronomically large number of permutations. For example, there are about 10^74 ways a deck of 56 cards can be shuffled. The random number generator’s internal state is not that large, which means there are many permutations it will never generate.