wren/doc/site/modules/random/random.markdown

^title 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

[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.