Darklang.Stdlib.List

Functions for working with lists — the primary collection type in Darklang.

⚡ 18 functions 💎 1 value

let empty = []

Returns an empty list

let singleton (value: 'a) : List<'a>

Returns a one-element list containing the given value.

let head (list: List<'a>) : Option.Option<'a>

Returns Some the head (first value) of a list. Returns None if the list is empty.

let tail (list: List<'a>) : Option.Option<List<'a>>

If the list contains at least one value, returns Some with a list of every value other than the first. Otherwise, returns None.

let append (as: List<'a>) (bs: List<'a>) : List<'a>

Returns a new list with all values in as followed by all values in bs, preserving the order.

let push (list: List<'a>) (value: 'a) : List<'a>

Add element to front of list.

let last (list: List<'a>) : Option.Option<'a>

Returns the last value in the list, wrapped in an option (None if the list is empty).

let reverse (list: List<'a>) : List<'a>

Returns a reversed copy of the list.

let findFirst (list: List<'a>) (fn: 'a -> Bool) : Option.Option<'a>

Returns Some firstMatch where firstMatch is the first value of the list for which fn returns true. Returns None if no such value exists.

let member (list: List<'a>) (value: 'a) : Bool

Returns true if value is in the list.

let repeat (times: Int64) (value: 'a) : Result.Result<List<'a>, String>

Returns a list containing value repeated times times.

let length (list: List<'a>) : Int64

Returns the number of values in the list.

let range (lowest: Int64) (highest: Int64) : List<Int64>

Returns a list of numbers where each element is 1 larger than the previous. You provide the lowest and highest numbers in the list.

let fold (list: List<'a>) (init: 'b) (fn: 'b -> 'a -> 'b) : 'b

Folds list into a single value, by repeatedly applying fn to any two pairs.

let flatten (list: List<List<'a>>) : List<'a>

Returns a single list containing the values of every list directly in list (does not recursively flatten nested lists).

let map (list: List<'a>) (fn: 'a -> 'b) : List<'b>

Applies fn to each element of list and returns the new list.

let sort (list: List<'a>) : List<'a>

Returns a copy of list with every value sorted in ascending order.

let unique (list: List<'a>) : List<'a>

Returns the list with only unique values. Order will not be maintained.

let isEmpty (list: List<'a>) : Bool

Returns true if the list has no values.

type Option<'v> = | Some of 'v | None

type Result<'Ok, 'Err> = | Ok of 'Ok | Error of 'Err