Stdlib: Add Array.filterMapWithIndex (#7876)

* Add filterMapWithIndex to Stdlib

* Changelog

Author: fhammerschmidt

CHANGELOG.md

@@ -20,6 +20,8 @@
 
 #### :rocket: New Feature
 
+- Add `Array.filterMapWithIndex` to Stdlib. https://github.com/rescript-lang/rescript/pull/7876
+
 #### :bug: Bug fix
 
 - Fix code generation for emojis in polyvars and labels. https://github.com/rescript-lang/rescript/pull/7853

packages/@rescript/runtime/Stdlib_Array.res

@@ -273,6 +273,23 @@ let filterMap = (a, f) => {
 
 let keepSome = filterMap(_, x => x)
 
+let filterMapWithIndex = (a, f) => {
+  let l = length(a)
+  let r = makeUninitializedUnsafe(l)
+  let j = ref(0)
+  for i in 0 to l - 1 {
+    let v = getUnsafe(a, i)
+    switch f(v, i) {
+    | None => ()
+    | Some(v) =>
+      setUnsafe(r, j.contents, v)
+      j.contents = j.contents + 1
+    }
+  }
+  truncateToLengthUnsafe(r, j.contents)
+  r
+}
+
 @send external flatMap: (array<'a>, 'a => array<'b>) => array<'b> = "flatMap"
 @send external flatMapWithIndex: (array<'a>, ('a, int) => array<'b>) => array<'b> = "flatMap"
 

packages/@rescript/runtime/Stdlib_Array.resi

@@ -1193,6 +1193,24 @@ Array.filterMap([], n => mod(n, 2) == 0 ? Some(n * n) : None) == []
 */
 let filterMap: (array<'a>, 'a => option<'b>) => array<'b>
 
+/**
+`filterMapWithIndex(array, fn)`
+
+Calls `fn` for each element and returns a new array containing results of the `fn` calls which are not `None`.
+
+## Examples
+
+```rescript
+["Hello", "Hi", "Good bye"]->Array.filterMapWithIndex((item, index) =>
+  switch item {
+  | "Hello" => Some(index)
+  | _ => None
+  }
+) == [0]
+```
+*/
+let filterMapWithIndex: (array<'a>, ('a, int) => option<'b>) => array<'b>
+
 /**
 `keepSome(arr)`
 

packages/@rescript/runtime/lib/es6/Stdlib_Array.js

@@ -162,6 +162,23 @@ function keepSome(__x) {
   return filterMap(__x, x => x);
 }
 
+function filterMapWithIndex(a, f) {
+  let l = a.length;
+  let r = new Array(l);
+  let j = 0;
+  for (let i = 0; i < l; ++i) {
+    let v = a[i];
+    let v$1 = f(v, i);
+    if (v$1 !== undefined) {
+      r[j] = Primitive_option.valFromOption(v$1);
+      j = j + 1 | 0;
+    }
+    
+  }
+  r.length = j;
+  return r;
+}
+
 function findMap(arr, f) {
   let _i = 0;
   while (true) {
@@ -197,6 +214,7 @@ export {
   findIndexOpt,
   findLastIndexOpt,
   filterMap,
+  filterMapWithIndex,
   keepSome,
   toShuffled,
   shuffle,

packages/@rescript/runtime/lib/js/Stdlib_Array.js

@@ -162,6 +162,23 @@ function keepSome(__x) {
   return filterMap(__x, x => x);
 }
 
+function filterMapWithIndex(a, f) {
+  let l = a.length;
+  let r = new Array(l);
+  let j = 0;
+  for (let i = 0; i < l; ++i) {
+    let v = a[i];
+    let v$1 = f(v, i);
+    if (v$1 !== undefined) {
+      r[j] = Primitive_option.valFromOption(v$1);
+      j = j + 1 | 0;
+    }
+    
+  }
+  r.length = j;
+  return r;
+}
+
 function findMap(arr, f) {
   let _i = 0;
   while (true) {
@@ -196,6 +213,7 @@ exports.reduceRightWithIndex = reduceRightWithIndex;
 exports.findIndexOpt = findIndexOpt;
 exports.findLastIndexOpt = findLastIndexOpt;
 exports.filterMap = filterMap;
+exports.filterMapWithIndex = filterMapWithIndex;
 exports.keepSome = keepSome;
 exports.toShuffled = toShuffled;
 exports.shuffle = shuffle;

tests/analysis_tests/tests/src/expected/Completion.res.txt

@@ -238,6 +238,12 @@ Path Array.
     "tags": [],
     "detail": "(array<'a>, ('a, 'a) => Ordering.t) => unit",
     "documentation": {"kind": "markdown", "value": "\n`sort(array, comparator)` sorts `array` in-place using the `comparator` function.\n\nBeware this will *mutate* the array.\n\nSee [`Array.sort`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/sort) on MDN.\n\n## Examples\n\n```rescript\nlet array = [3, 2, 1]\narray->Array.sort((a, b) => float(a - b))\narray == [1, 2, 3]\n```\n"}
+  }, {
+    "label": "filterMapWithIndex",
+    "kind": 12,
+    "tags": [],
+    "detail": "(array<'a>, ('a, int) => option<'b>) => array<'b>",
+    "documentation": {"kind": "markdown", "value": "\n`filterMapWithIndex(array, fn)`\n\nCalls `fn` for each element and returns a new array containing results of the `fn` calls which are not `None`.\n\n## Examples\n\n```rescript\n[\"Hello\", \"Hi\", \"Good bye\"]->Array.filterMapWithIndex((item, index) =>\n  switch item {\n  | \"Hello\" => Some(index)\n  | _ => None\n  }\n) == [0]\n```\n"}
   }, {
     "label": "length",
     "kind": 12,

tests/analysis_tests/tests/src/expected/DotPipeCompletionSpec.res.txt

@@ -374,6 +374,18 @@ Path filt
       "range": {"start": {"line": 86, "character": 34}, "end": {"line": 86, "character": 35}},
       "newText": ""
       }]
+  }, {
+    "label": "->Array.filterMapWithIndex",
+    "kind": 12,
+    "tags": [],
+    "detail": "(array<'a>, ('a, int) => option<'b>) => array<'b>",
+    "documentation": {"kind": "markdown", "value": "\n`filterMapWithIndex(array, fn)`\n\nCalls `fn` for each element and returns a new array containing results of the `fn` calls which are not `None`.\n\n## Examples\n\n```rescript\n[\"Hello\", \"Hi\", \"Good bye\"]->Array.filterMapWithIndex((item, index) =>\n  switch item {\n  | \"Hello\" => Some(index)\n  | _ => None\n  }\n) == [0]\n```\n"},
+    "sortText": "filterMapWithIndex",
+    "insertText": "->Array.filterMapWithIndex",
+    "additionalTextEdits": [{
+      "range": {"start": {"line": 86, "character": 34}, "end": {"line": 86, "character": 35}},
+      "newText": ""
+      }]
   }, {
     "label": "->Array.filter",
     "kind": 12,