iterator.each (#431)

Author: aslilac

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Changelog
 
+## Unreleased
+
+- The `iterator` module gains the `each` function.
+
 ## v0.28.0 - 2023-03-26
 
 - `regex.scan` now behaves consistently across both targets when a capture group does not capture anything.

src/gleam/iterator.gleam

@@ -1417,3 +1417,26 @@ pub fn length(over iterator: Iterator(e)) -> Int {
   iterator.continuation
   |> do_length(0)
 }
+
+/// Traverse an iterator, calling a function on each element.
+///
+/// ## Examples
+///
+/// ```gleam
+/// > empty() |> each(io.println)
+/// Nil
+/// ```
+///
+/// ```gleam
+/// > from_list(["Tom", "Malory", "Louis"]) |> each(io.println)
+/// // -> Tom
+/// // -> Malory
+/// // -> Louis
+/// Nil
+/// ```
+///
+pub fn each(over iterator: Iterator(a), with f: fn(a) -> b) -> Nil {
+  iterator
+  |> map(f)
+  |> run
+}

test/gleam/iterator_test.gleam

@@ -584,3 +584,9 @@ pub fn length_test() {
   |> iterator.length
   |> should.equal(0)
 }
+
+pub fn each_test() {
+  use it <- iterator.each(iterator.from_list([1]))
+  it
+  |> should.equal(1)
+}