Stream
module Stream
Sequence
Sequence(from: A, step: (A -> A)) -> Stream<A>Creates an infinite stream starting at from, applying step to produce each successive element.
Parameters
from- the first element
step- produces the next element from the current one
Examples
let naturals = Stream.Sequence(from: 0) { |n| n + 1 }
naturals.take(5) # => [0, 1, 2, 3, 4]
let powers = Stream.Sequence(from: 1) { |n| n * 2 }
powers.take(6) # => [1, 2, 4, 8, 16, 32]Iterate
Iterate(seed: A, step) -> Stream<A>Creates an infinite stream seeded with seed, applying f to each element to produce the next. Equivalent to Sequence; use whichever reads more clearly at the call site.
Parameters
seedf
Examples
let odds = Stream.Iterate(1) { |n| n + 2 }
odds.take(5) # => [1, 3, 5, 7, 9]type Stream<A>
take
take(n: Integer) -> [A]Returns the first n elements as a list. Evaluates the stream up to that point.
Parameters
n
Examples
Stream.Sequence(from: 1) { |n| n + 1 }.take(3) # => [1, 2, 3]drop
drop(n: Integer) -> Stream<A>Skips the first n elements and returns a new stream offset by n.
Parameters
n
Examples
Stream.Sequence(from: 0) { |n| n + 1 }.drop(3).take(3) # => [3, 4, 5]map
map(f: (A -> B)) -> Stream<B>Returns a new stream applying f to each element.
Parameters
f
Examples
Stream.Sequence(from: 1) { |n| n + 1 }.map { |n| n * n }.take(4)
# => [1, 4, 9, 16]filter
filter(pred: (A -> Bool)) -> Stream<A>Returns a new stream keeping only elements for which pred is true. Note: consuming n elements may require evaluating many upstream elements.
Parameters
pred
Examples
let evens = Stream.Sequence(from: 0) { |n| n + 1 }.filter { |n| n.even? }
evens.take(4) # => [0, 2, 4, 6]