Add Array.last

rescript-lang · Dec 30, 2023 · 4e73a95 · 4e73a95
1 parent 19183c1
commit 4e73a95
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Showing 5 changed files with 49 additions and 0 deletions.
diff --git a/src/Core__Array.mjs b/src/Core__Array.mjs
@@ -167,6 +167,10 @@ function findMap(arr, f) {
   };
 }
 
+function last(a) {
+  return a[a.length - 1 | 0];
+}
+
 export {
   make ,
   fromInitializer ,
@@ -184,5 +188,6 @@ export {
   toShuffled ,
   shuffle ,
   findMap ,
+  last ,
 }
 /* No side effect */
diff --git a/src/Core__Array.res b/src/Core__Array.res
@@ -248,3 +248,5 @@ let findMap = (arr, f) => {
 }
 
 @send external at: (array<'a>, int) => option<'a> = "at"
+
+let last = a => a->get(a->length - 1)
diff --git a/src/Core__Array.resi b/src/Core__Array.resi
@@ -993,3 +993,18 @@ let findMap: (array<'a>, 'a => option<'b>) => option<'b>
 */
 @send
 external at: (array<'a>, int) => option<'a> = "at"
+
+/**
+`last(array)` returns the last element of `array`.
+
+Returns `None` if the array is empty.
+
+## Examples
+```rescript
+let array = ["Hello", "Hi", "Good bye"]
+
+array->Array.last == Some("Good bye") // true
+[]->Array.last == None // true
+```
+*/
+let last: array<'a> => option<'a>
diff --git a/test/ArrayTests.mjs b/test/ArrayTests.mjs
@@ -447,6 +447,30 @@ Test.run([
       4
     ]);
 
+Test.run([
+      [
+        "ArrayTests.res",
+        109,
+        20,
+        39
+      ],
+      "last - with items"
+    ], Core__Array.last([
+          1,
+          2,
+          3
+        ]), eq, 3);
+
+Test.run([
+      [
+        "ArrayTests.res",
+        110,
+        20,
+        34
+      ],
+      "last - empty"
+    ], Core__Array.last([]), eq, undefined);
+
 export {
   eq ,
 }

diff --git a/test/ArrayTests.res b/test/ArrayTests.res
@@ -108,3 +108,6 @@ Test.run(
   eq,
   [3, 4],
 )
+
+Test.run(__POS_OF__("last - with items"), [1, 2, 3]->Array.last, eq, Some(3))
+Test.run(__POS_OF__("last - empty"), []->Array.last, eq, None)