gleam_zlists - gleam

all

pub fn all(zlist: ZList(a), fun: fn(a) -> Bool) -> Bool

Iterates over the zlist and invokes fun on each element. When an invocation of fun returns False, iteration stops immediately and False is returned. In all other cases True is returned.

Examples

[2, 4, 6]
|> of_list
|> all(int.is_even)
True

[2, 3, 4]
|> of_list
|> all(int.is_even)
False

[]
|> of_list
|> all(fn(x) { x > 0 })
True

any

</>

pub fn any(zlist: ZList(a), fun: fn(a) -> Bool) -> Bool

Iterates over the zlist and invokes fun on each element. When an invocation of fun returns True, iteration stops immediately and True is returned. In all other cases False is returned.

Examples

[2, 4, 6]
|> of_list
|> any(int.is_odd)
False

[2, 3, 4]
|> of_list
|> any(int.is_odd)
True

[]
|> of_list
|> any(fn(x) { x > 0 })
False

append

</>

pub fn append(left: ZList(a), right: ZList(a)) -> ZList(a)

Creates a ZList that contains the first argument, followed by the second.

Examples

append(range(1, 3, 1), range(4, 6, 1))
|> to_list
[1, 2, 3, 4, 5, 6]

concat

</>

pub fn concat(zlists: ZList(ZList(a))) -> ZList(a)

Given an ZList of ZList, concatenates them into a single ZList.

Examples

[range(1, 3, 1), range(4, 6, 1), range(7, 9, 1)]
|> of_list
|> concat
|> to_list
[1, 2, 3, 4, 5, 6, 7, 8, 9]

cons

</>

pub fn cons(zlist: ZList(a), first_value: a) -> ZList(a)

Return a new ZList which contains the first_value followed by the zlist.

Examples

range(1, 3, 1)
|> cons(0)
|> to_list
[0, 1, 2, 3]

Examples

[1, 2, 3]
|> of_list
|> count
3

dedup

</>

pub fn dedup(zlist: ZList(a)) -> ZList(a)

Creates a ZList that only emits elements if they are different from the last emitted element. This function only ever needs to store the last emitted element.

Examples

 [1, 2, 3, 3, 2, 1]
 |> of_list
 |> dedup
 |> to_list
 [1, 2, 3, 2, 1]

drop

</>

pub fn drop(zlist: ZList(a), n: Int) -> ZList(a)

Lazily drops the next n elements from the zlist. n should not be negative.

Examples

[1, 2, 3]
|> of_list
|> drop(2)
|> to_list
[3]

drop_while

</>

pub fn drop_while(
  zlist: ZList(a),
  fun: fn(a) -> Bool,
) -> ZList(a)

Drops elements at the beginning of the zlist while fun returns a True.

Examples

[1, 2, 3, 2, 1]
|> of_list
|> drop_while(fn(x) { x < 3 })
|> to_list
[3, 2, 1]

each

</>

pub fn each(zlist: ZList(a), fun: fn(a) -> b) -> Nil

Executes the given function for each element. Useful for adding side effects (like printing) to a ZList.

fetch

</>

pub fn fetch(zlist: ZList(a), index: Int) -> Result(a, Nil)

Finds the element at the given index (zero-based). Returns Ok(element) if found, otherwise Error(Nil).

Examples

[2, 4, 6]
|> of_list
|> fetch(1)
Ok(4)

[2, 4, 6]
|> of_list
|> fetch(4)
Error(Nil)

filter

</>

pub fn filter(zlist: ZList(a), fun: fn(a) -> Bool) -> ZList(a)

Filters the zlist, i.e. returns only those elements for which fun returns True.

Examples

[1, 2, 3]
|> of_list
|> filter(fn(x) { int.is_even(x) })
|> to_list
[2]

find

</>

pub fn find(
  zlist: ZList(a),
  fun: fn(a) -> Bool,
) -> Result(a, Nil)

Returns Ok(element) for the first element that fun returns True. If no such element is found, returns Error(Nil).

Examples

[2, 3, 4]
|> of_list
|> find(int.is_odd)
Ok(3)

[2, 4, 6]
|> of_list
|> find(int.is_odd)
Error(Nil)

flat_map

</>

pub fn flat_map(
  zlist: ZList(a),
  fun: fn(a) -> ZList(b),
) -> ZList(b)

Maps the given fun over zlist and flattens the result. This function returns a new ZList built by appending the result of invoking fun on each element of zlist together.

Examples

[1, 2, 3]
|> of_list
|> flat_map(fn(x) { of_list([x, 2 * x]) })
|> to_list
[1, 2, 2, 4, 3, 6]

has_member

</>

pub fn has_member(zlist: ZList(a), element: a) -> Bool

Checks if element exists within the zlist.

Examples

[2, 3, 4]
|> of_list
|> has_member(3)
True

[2, 4, 6]
|> of_list
|> has_member(8)
False

head

</>

pub fn head(zlist: ZList(a)) -> Result(a, Nil)

Gets the first element of the zlist, if there is one.

Examples

range(1, 3, 1)
|> head
Ok(1)

new()
|> head
Error(Nil)

indices

</>

pub fn indices() -> ZList(Int)

Returns an infinite ZList that contains the non-negative integers (sorted).

Examples

indices()
|> take(5)
|> to_list
[0, 1, 2, 3, 4]

Examples

[]
|> of_list
|> is_empty
True

[1, 2, 3]
|> of_list
|> is_empty
False

iterate

</>

pub fn iterate(start_value: a, next_fun: fn(a) -> a) -> ZList(a)

Emits a ZList of values, starting with start_value. Successive values are generated by calling next_fun on the previous value.

Examples

iterate(0, fn(x) { x + 1 })
|> take(5)
|> to_list
[0, 1, 2, 3, 4]

map

</>

pub fn map(zlist: ZList(a), fun: fn(a) -> b) -> ZList(b)

Returns a ZList where each element is the result of invoking fun on each corresponding element of zlist.

Examples

[1, 2, 3]
|> of_list
|> map(fn(x) { 2 * x })
|> to_list
[2, 4, 6]

Examples

new()
|> to_list
[]

range

</>

pub fn range(first: Int, last: Int, step: Int) -> ZList(Int)

Returns a lazy range from first to last (included). The difference between one term and the next equals to step. The step should be positive.

Examples

range(0, 3, 1)
|> to_list
[0, 1, 2, 3]

range(-3, 5, 2)
|> to_list
[-3, -1, 1, 3, 5]

reduce

</>

pub fn reduce(zlist: ZList(a), acc: b, fun: fn(a, b) -> b) -> b

Invokes fun for each element in the zlist with the accumulator. The initial value of the accumulator is acc. The function is invoked for each element in the zlist with the accumulator. The result returned by the function is used as the accumulator for the next iteration. The function returns the last accumulator.

Examples

[1, 2, 3]
|> of_list
|> reduce(0, fn(x, acc) { x + acc })
6

reverse

</>

pub fn reverse(zlist: ZList(a)) -> ZList(a)

Returns a ZList of the elements in zlist in reverse order.

Examples

[1, 2, 3]
|> of_list
|> reverse
|> to_list
[3, 2, 1]

singleton

</>

pub fn singleton(value: a) -> ZList(a)

Creates a ZList of just one specified value.

Examples

10
|> singleton
|> to_list
[10]

slice

</>

pub fn slice(
  zlist: ZList(a),
  start_index: Int,
  amount: Int,
) -> ZList(a)

Returns a subset ZList of the given zlist, from start_index (zero-based) with amount number of elements if available. Given an zlist, it drops elements right before element start_index, then takes amount of elements, returning as many elements as possible if there are not enough elements.

Examples

range(1, 100, 1)
|> slice(5, 10)
|> to_list
[6, 7, 8, 9, 10, 11, 12, 13, 14, 15]

range(1, 10, 1)
|> slice(5, 100)
|> to_list
[6, 7, 8, 9, 10]

split

</>

pub fn split(zlist: ZList(a), n: Int) -> tuple(List(a), ZList(a))

Splits the zlist into a List and a ZList, leaving n elements in the first one.

Examples

let tuple(ls_a, zls_b) =
  [1, 2, 3]
  |> of_list
  |> split(2)
let ls_b = to_list(zls_b)
tuple(ls_a, ls_b)
tuple([1, 2], [3])

split_while

</>

pub fn split_while(
  zlist: ZList(a),
  fun: fn(a) -> Bool,
) -> tuple(List(a), ZList(a))

Splits zlist into a List and a ZList at the position of the element for which fun returns False for the first time.

Examples

let tuple(ls_a, zls_b) =
  [1, 2, 3, 4]
  |> of_list
  |> split_while(fn(x) { x < 3 })
let ls_b = to_list(zls_b)
tuple(ls_a, ls_b)
tuple([1, 2], [3, 4])

tail

</>

pub fn tail(zlist: ZList(a)) -> Result(ZList(a), Nil)

Gets the zlist minus the first element. If the zlist is empty, Error(Nil) is returned.

Examples

range(1, 3, 1)
|> tail
|> result.map(to_list)
Ok([2, 3])

new()
|> tail
Error(Nil)

take

</>

pub fn take(zlist: ZList(a), n: Int) -> ZList(a)

Lazily takes the first n elements from the zlist. The n should not be negative.

Examples

range(1, 100, 1)
|> take(5)
|> to_list
[1, 2, 3, 4, 5]

take_while

</>

pub fn take_while(
  zlist: ZList(a),
  fun: fn(a) -> Bool,
) -> ZList(a)

Lazily takes elements of the zlist while the given function returns True.

Examples

range(1, 100, 1)
|> take_while(fn(x) { x <= 5 })
|> to_list
[1, 2, 3, 4, 5]

to_list

</>

pub fn to_list(zlist: ZList(a)) -> List(a)

Converts a zlist to List.

Examples

range(0, 3, 1)
|> to_list
[0, 1, 2, 3]

uncons

</>

pub fn uncons(zlist: ZList(a)) -> Result(tuple(a, ZList(a)), Nil)

Returns the tuple of the first element and the tail of the zlist. If the zlist is empty, Error(Nil) is returned.

Examples

range(1, 3, 1)
|> uncons
|> result.map(fn(res) {
  let tuple(hd, tl) = res
  tuple(hd, to_list(tl))
})
Ok(tuple(1, [2, 3]))

with_index

</>

pub fn with_index(zlist: ZList(a)) -> ZList(tuple(a, Int))

Returns the zlist with each element wrapped in a tuple alongside its index.

Examples

["a", "b", "c"]
|> of_list
|> with_index
|> to_list
[tuple("a", 0), tuple("b", 1), tuple("c", 2)]

zip

</>

pub fn zip(left: ZList(a), right: ZList(b)) -> ZList(tuple(a, b))

Zips left and right together, lazily. The zipping finishes as soon as any ZList completes.

Examples

let left = of_list([1, 2, 3])
let right = of_list(["foo", "bar", "baz"])
zip(left, right)
|> to_list
[tuple(1, "foo"), tuple(2, "bar"), tuple(3, "baz")]