feat(array): add reduceRightWithIndex

Author: glennsl

src/Core__Array.res

@@ -131,6 +131,8 @@ let sort = (arr, cmp) => {
 @send external reduceWithIndex: (array<'b>, ('a, 'b, int) => 'a, 'a) => 'a = "reduce"
 @send
 external reduceRight: (array<'b>, ('a, 'b) => 'a, 'a) => 'a = "reduceRight"
+@send
+external reduceRightWithIndex: (array<'b>, ('a, 'b, int) => 'a, 'a) => 'a = "reduceRight"
 
 @send external some: (array<'a>, 'a => bool) => bool = "some"
 @send external someWithIndex: (array<'a>, ('a, int) => bool) => bool = "some"

src/Core__Array.resi

@@ -96,6 +96,18 @@ external reduceWithIndex: (array<'b>, ('a, 'b, int) => 'a, 'a) => 'a = "reduce"
 @send
 external reduceRight: (array<'b>, ('a, 'b) => 'a, 'a) => 'a = "reduceRight"
 
+/**
+  `reduceRightWithIndex(xs, f, init)`
+
+  Like `reduceRight`, but with an additional index argument on the callback function.
+
+  ```res example
+  Array.reduceRightWithIndex([1, 2, 3, 4], (acc, x, i) => acc + x + i, 0) == 16
+  ```
+*/
+@send
+external reduceRightWithIndex: (array<'b>, ('a, 'b, int) => 'a, 'a) => 'a = "reduceRight"
+
 @send external some: (array<'a>, 'a => bool) => bool = "some"
 @send external someWithIndex: (array<'a>, ('a, int) => bool) => bool = "some"
 @get_index external get: (array<'a>, int) => option<'a> = ""

test/ArrayTests.mjs

@@ -156,7 +156,50 @@ Test.run([
 Test.run([
       [
         "ArrayTests.res",
-        38,
+        39,
+        13,
+        35
+      ],
+      "reduceEightWithIndex"
+    ], [
+        1,
+        2,
+        3
+      ].reduceRight((function (acc, v, i) {
+            return {
+                    hd: v + i | 0,
+                    tl: acc
+                  };
+          }), /* [] */0), eq, {
+      hd: 1,
+      tl: {
+        hd: 3,
+        tl: {
+          hd: 5,
+          tl: /* [] */0
+        }
+      }
+    });
+
+Test.run([
+      [
+        "ArrayTests.res",
+        45,
+        13,
+        38
+      ],
+      "reduceWithIndex - empty"
+    ], [].reduceRight((function (acc, v, i) {
+            return {
+                    hd: v + i | 0,
+                    tl: acc
+                  };
+          }), /* [] */0), eq, /* [] */0);
+
+Test.run([
+      [
+        "ArrayTests.res",
+        51,
         20,
         38
       ],
@@ -176,7 +219,7 @@ var arr = [
 Test.run([
       [
         "ArrayTests.res",
-        41,
+        54,
         13,
         38
       ],
@@ -186,7 +229,7 @@ Test.run([
 Test.run([
       [
         "ArrayTests.res",
-        52,
+        65,
         13,
         24
       ],
@@ -212,7 +255,7 @@ Test.run([
 Test.run([
       [
         "ArrayTests.res",
-        57,
+        70,
         20,
         42
       ],
@@ -231,7 +274,7 @@ Test.run([
 Test.run([
       [
         "ArrayTests.res",
-        59,
+        72,
         13,
         32
       ],
@@ -246,7 +289,7 @@ Test.run([
 Test.run([
       [
         "ArrayTests.res",
-        65,
+        78,
         20,
         30
       ],
@@ -263,7 +306,7 @@ Test.run([
 Test.run([
       [
         "ArrayTests.res",
-        67,
+        80,
         13,
         34
       ],
@@ -281,7 +324,7 @@ Test.run([
 Test.run([
       [
         "ArrayTests.res",
-        72,
+        85,
         20,
         41
       ],
@@ -295,7 +338,7 @@ Test.run([
 Test.run([
       [
         "ArrayTests.res",
-        73,
+        86,
         20,
         38
       ],
@@ -305,7 +348,7 @@ Test.run([
 Test.run([
       [
         "ArrayTests.res",
-        76,
+        89,
         13,
         22
       ],
@@ -327,7 +370,7 @@ Test.run([
 Test.run([
       [
         "ArrayTests.res",
-        81,
+        94,
         20,
         40
       ],
@@ -346,7 +389,7 @@ Test.run([
 Test.run([
       [
         "ArrayTests.res",
-        83,
+        96,
         13,
         30
       ],

test/ArrayTests.res

@@ -35,6 +35,19 @@ Test.run(
 )
 Test.run(__POS_OF__("reduceRight - empty"), Array.reduceRight([], List.add, list{}), eq, list{})
 
+Test.run(
+  __POS_OF__("reduceEightWithIndex"),
+  Array.reduceRightWithIndex([1, 2, 3], (acc, v, i) => list{v + i, ...acc}, list{}),
+  eq,
+  list{1, 3, 5},
+)
+Test.run(
+  __POS_OF__("reduceWithIndex - empty"),
+  Array.reduceRightWithIndex([], (acc, v, i) => list{v + i, ...acc}, list{}),
+  eq,
+  list{},
+)
+
 Test.run(__POS_OF__("shuffle - length"), Array.shuffle([1, 2, 3])->Array.length, eq, 3)
 
 Test.run(