Add `last` function to `String`s.

2 files changed, 37 insertions, 0 deletions

diff --git a/src/gleam/string.gleam b/src/gleam/string.gleam
index ac7d3aa..3cec7d2 100644
--- a/src/gleam/string.gleam
+++ b/src/gleam/string.gleam
@@ -762,3 +762,26 @@ pub fn first(s: String) -> Option(String) {
     _ -> Some(slice(s, 0, 1))
   }
 }
+
+/// Returns the last element in a grapheme and wraps it in an `Option(String)`.
+/// If the `String` is empty, it returns `None`. Otherwise, it returns
+/// `Some(String)`.
+///
+/// ## Examples
+///
+/// ```gleam
+/// > last("")
+/// None
+/// ```
+///
+/// ```gleam
+/// > last("icecream")
+/// Some("m")
+/// ```
+///
+pub fn last(s: String) -> Option(String) {
+  case length(s) {
+    0 -> None
+    _ -> Some(slice(s, length(s) - 1, 1))
+  }
+}
diff --git a/test/gleam/string_test.gleam b/test/gleam/string_test.gleam
index a98a2e2..8ad1080 100644
--- a/test/gleam/string_test.gleam
+++ b/test/gleam/string_test.gleam
@@ -374,3 +374,17 @@ pub fn first_test() {
   |> string.first
   |> should.equal(Some("g"))
 }
+
+pub fn last_test() {
+  ""
+  |> string.last
+  |> should.equal(None)
+
+  "gleam"
+  |> string.last
+  |> should.equal(Some("m"))
+
+  "gleam "
+  |> string.last
+  |> should.equal(Some(" "))
+}