rand

Random integer sampling, string generation, selection, and shuffling.

Functions

`int start … -> Int`

Samples a uniformly distributed integer from [0, end) or [start, end).

Parameters

Name	Type	Description
`start`	`Int`	Inclusive lower bound, or the exclusive upper bound when `end` is omitted.
`end?`	`Int`	Exclusive upper bound.

Errors

Exception	Condition
`TypeError`	Either argument is not an integer
`ValueError`	`end <= 0`, or `end <= start` if given

Example

assert_eq (int 1) 0
let n = int 10 20
assert ((n >= 10) && (n < 20))

`pick[T] collection -> T`

Selects one random element from an array.

Parameters

Name	Type	Description
`collection`	`Array[T]`	Source array.

Errors

TypeError if collection is not an array. ValueError if it is empty.

Example

let item = pick [1, 2, 3]
assert ([1, 2, 3].contains $item)

`shuffle array`

Shuffles an array in place using a uniform Fisher-Yates pass.

Parameters

Name	Type	Description
`array`	`Array[Value]`	Array to mutate.

Errors

TypeError if array is not an array.

Example

let items = [1, 2, 3, 4]
shuffle $items
let sorted = [...items]
sorted.sort()
assert_eq $sorted [1, 2, 3, 4]

Open in playground

`string len … -> Str`

Generates a random string by sampling characters from alphabet.

Parameters

Name	Type	Description
`len`	`Int`	Number of characters to emit.
`:alphabet?`	`Str`	Characters to sample from.

`:alphabet`

The alphabet is interpreted as characters, not raw UTF-8 bytes. When omitted, it is _-0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ.

Errors

TypeError if len is not an integer or alphabet is not a string. ValueError if len is negative or alphabet is empty.

Example

let token = string 12
assert_eq $token.len 12

let text = string 4 alphabet: "åß"
assert_eq $text.len 8