feat(array): add init

Author: glennsl

src/Core__Array.mjs

@@ -5,6 +5,17 @@ import * as Js_math from "rescript/lib/es6/js_math.js";
 import * as Caml_option from "rescript/lib/es6/caml_option.js";
 import * as Caml_splice_call from "rescript/lib/es6/caml_splice_call.js";
 
+function init(len, f) {
+  if (len <= 0) {
+    return [];
+  }
+  var arr = new Array(len);
+  for(var i = 0; i < len; ++i){
+    arr[i] = Curry._1(f, i);
+  }
+  return arr;
+}
+
 function indexOfOpt(arr, item) {
   var index = arr.indexOf(item);
   if (index !== -1) {
@@ -123,6 +134,7 @@ function findMap(arr, f) {
 }
 
 export {
+  init ,
   indexOfOpt ,
   lastIndexOfOpt ,
   reduce ,

src/Core__Array.res

@@ -1,3 +1,5 @@
+@new external makeUninitializedUnsafe: int => array<'a> = "Array"
+@set external truncateToLengthUnsafe: (array<'a>, int) => unit = "length"
 external getUnsafe: (array<'a>, int) => 'a = "%array_unsafe_get"
 external setUnsafe: (array<'a>, int, 'a) => unit = "%array_unsafe_set"
 
@@ -11,6 +13,17 @@ external fromArrayLikeWithMap: (Js.Array2.array_like<'a>, 'a => 'b) => array<'a>
 @val external fromIterator: Core__Iterator.t<'a> => array<'a> = "Array.from"
 @val external fromIteratorWithMap: (Core__Iterator.t<'a>, 'a => 'c) => array<'a> = "Array.from"
 
+let init = (len, f) =>
+  if len <= 0 {
+    []
+  } else {
+    let arr = makeUninitializedUnsafe(len)
+    for i in 0 to len - 1 {
+      arr->setUnsafe(i, f(i))
+    }
+    arr
+  }
+
 @val external isArray: 'a => bool = "Array.isArray"
 
 @get external length: array<'a> => int = "length"
@@ -145,8 +158,6 @@ let findIndexOpt = (array: array<'a>, finder: 'a => bool): option<int> =>
   | index => Some(index)
   }
 
-@new external makeUninitializedUnsafe: int => array<'a> = "Array"
-@set external truncateToLengthUnsafe: (array<'a>, int) => unit = "length"
 let swapUnsafe = (xs, i, j) => {
   let tmp = getUnsafe(xs, i)
   setUnsafe(xs, i, getUnsafe(xs, j))

src/Core__Array.resi

@@ -5,6 +5,7 @@
 external fromArrayLikeWithMap: (Js.Array2.array_like<'a>, 'a => 'b) => array<'a> = "Array.from"
 @val external fromIterator: Core__Iterator.t<'a> => array<'a> = "Array.from"
 @val external fromIteratorWithMap: (Core__Iterator.t<'a>, 'a => 'c) => array<'a> = "Array.from"
+let init: (int, int => 'a) => array<'a>
 @val external isArray: 'a => bool = "Array.isArray"
 @get external length: array<'a> => int = "length"
 @send external copyAllWithin: (array<'a>, ~target: int) => array<'a> = "copyWithin"