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-rw-r--r--src/gleam/iterator.gleam20
-rw-r--r--test/gleam/iterator_test.gleam25
2 files changed, 43 insertions, 2 deletions
diff --git a/src/gleam/iterator.gleam b/src/gleam/iterator.gleam
index 53b80d3..6634f23 100644
--- a/src/gleam/iterator.gleam
+++ b/src/gleam/iterator.gleam
@@ -63,7 +63,6 @@ pub fn repeat(x: element) -> Iterator(element) {
repeatedly(fn() { x })
}
-// TODO: test
// TODO: document
pub fn from_list(list: List(element)) -> Iterator(element) {
unfold(list, fn(acc) {
@@ -96,7 +95,6 @@ pub fn run(iterator) -> Nil {
fold(iterator, Nil, fn(_, acc) { acc })
}
-// TODO: test
// TODO: document
pub fn to_list(iterator: Iterator(element)) -> List(element) {
iterator
@@ -104,6 +102,24 @@ pub fn to_list(iterator: Iterator(element)) -> List(element) {
|> list.reverse
}
+fn do_take(iterator, desired, acc) {
+ case desired > 0 {
+ True -> case iterator() {
+ Continue(element, iterator) -> do_take(iterator, desired - 1, [element | acc])
+ Stop -> acc
+ }
+ False -> acc
+ }
+}
+
+// TODO: document
+pub fn take(from iterator: Iterator(e), up_to desired: Int) -> List(e) {
+ iterator
+ |> unopaque
+ |> do_take(_, desired, [])
+ |> list.reverse
+}
+
// Transforming Iterators
fn do_map(iterator, f) {
diff --git a/test/gleam/iterator_test.gleam b/test/gleam/iterator_test.gleam
index fbbf1c6..2d9ee3f 100644
--- a/test/gleam/iterator_test.gleam
+++ b/test/gleam/iterator_test.gleam
@@ -1,6 +1,10 @@
import gleam/expect
import gleam/iterator
+import gleam/list
+// TODO: Property tests
+
+// a |> from_list |> to_list == a
pub fn to_from_list_test() {
let test = fn(subject) {
subject
@@ -14,3 +18,24 @@ pub fn to_from_list_test() {
test([1, 2])
test([1, 2, 4, 8])
}
+
+// a |> from_list |> take(_, n) == a |> list.take(_, n)
+pub fn take_test() {
+ let test = fn(n, subject) {
+ subject
+ |> iterator.from_list
+ |> iterator.take(_, n)
+ |> expect.equal(_, list.take(subject, n))
+ }
+
+ test(0, [])
+ test(1, [])
+ test(-1, [])
+ test(0, [0])
+ test(1, [0])
+ test(-1, [0])
+ test(0, [0, 1, 2, 3, 4])
+ test(1, [0, 1, 2, 3, 4])
+ test(2, [0, 1, 2, 3, 4])
+ test(22, [0, 1, 2, 3, 4])
+}