stdlib additions

2 files changed, 85 insertions, 0 deletions

diff --git a/src/list.gleam b/src/list.gleam
index 6687acf..12b7cad 100644
--- a/src/list.gleam
+++ b/src/list.gleam
@@ -3,6 +3,9 @@ import expect
 pub enum Empty =
   | Empty
 
+pub enum NotFound =
+  | NotFound
+
 // Using the Erlang C BIF implementation.
 //
 pub external fn length(List(a)) -> Int = "erlang" "length"
@@ -279,3 +282,35 @@ test foldr {
     |> foldr(_, [], fn(x, acc) { [x | acc] })
     |> expect:equal(_, [1, 2, 3])
 }
+
+pub fn find(haystack, f) {
+  case haystack {
+  | [] -> Error(NotFound)
+  | [x | rest] ->
+      case f(x) {
+      | Ok(x) -> Ok(x)
+      | _ -> find(rest, f)
+      }
+  }
+}
+
+test find {
+  let f = fn(x) {
+    case x {
+    | 2 -> Ok(4)
+    | _ -> Error(NotFound)
+    }
+  }
+
+  [1, 2, 3]
+  |> find(_, f)
+  |> expect:equal(_, Ok(4))
+
+  [1, 3, 2]
+  |> find(_, f)
+  |> expect:equal(_, Ok(4))
+
+  [1, 3]
+  |> find(_, f)
+  |> expect:equal(_, Error(NotFound))
+}
diff --git a/src/tuple.gleam b/src/tuple.gleam
index d437a9f..5da1810 100644
--- a/src/tuple.gleam
+++ b/src/tuple.gleam
@@ -1,4 +1,18 @@
 import expect
+import result
+import list
+
+pub fn new(a, b) {
+  {a, b}
+}
+
+test new {
+  new(1, 2)
+  |> expect:equal(_, {1, 2})
+
+  new(2, "3")
+  |> expect:equal(_, {2, "3"})
+}
 
 pub fn first(tup) {
   let {a, _} = tup
@@ -21,3 +35,39 @@ test second {
   |> second
   |> expect:equal(_, 2)
 }
+
+pub fn swap(tup) {
+  let {a, b} = tup
+  {b, a}
+}
+
+test swap {
+  {1, "2"}
+  |> swap
+  |> expect:equal(_, {"2", 1})
+}
+
+pub fn fetch(haystack, needle) {
+  list:find(haystack, fn(tuple) {
+    case first(tuple) == needle {
+    | True -> Ok(second(tuple))
+    | False -> Error([])
+    }
+  })
+}
+
+test fetch {
+  let proplist = [{0, "1"}, {1, "2"}]
+
+  proplist
+  |> fetch(_, 0)
+  |> expect:equal(_, Ok("1"))
+
+  proplist
+  |> fetch(_, 1)
+  |> expect:equal(_, Ok("2"))
+
+  proplist
+  |> fetch(_, 2)
+  |> expect:is_error
+}