feat(int): add range and rangeWithOptions

Author: glennsl

src/Core__Int.mjs

@@ -1,5 +1,7 @@
 // Generated by ReScript, PLEASE EDIT WITH CARE
 
+import * as Pervasives from "rescript/lib/es6/pervasives.js";
+import * as Core__Array from "./Core__Array.mjs";
 
 function fromString(radix, x) {
   var maybeInt = radix !== undefined ? parseInt(x, radix) : parseInt(x);
@@ -10,6 +12,41 @@ function fromString(radix, x) {
   }
 }
 
+function rangeWithOptions(start, end, options) {
+  var isInverted = start > end;
+  var n = options.step;
+  var step;
+  if (n !== undefined) {
+    if (n !== 0) {
+      step = n;
+    } else {
+      if (start !== end) {
+        throw new RangeError("Incorrect range arguments");
+      }
+      step = n;
+    }
+  } else {
+    step = isInverted ? -1 : 1;
+  }
+  var length;
+  if (isInverted === step >= 0) {
+    length = 0;
+  } else if (step === 0) {
+    length = options.inclusive === true ? 1 : 0;
+  } else {
+    var range = isInverted ? start - end | 0 : end - start | 0;
+    var range$1 = options.inclusive === true ? range + 1 | 0 : range;
+    length = Math.ceil(range$1 / Pervasives.abs(step)) | 0;
+  }
+  return Core__Array.fromInitializer(length, (function (i) {
+                return start + Math.imul(i, step) | 0;
+              }));
+}
+
+function range(start, end) {
+  return rangeWithOptions(start, end, {});
+}
+
 var Constants = {
   minValue: -2147483648,
   maxValue: 2147483647
@@ -18,5 +55,7 @@ var Constants = {
 export {
   Constants ,
   fromString ,
+  range ,
+  rangeWithOptions ,
 }
 /* No side effect */

src/Core__Int.res

@@ -35,3 +35,29 @@ let fromString = (~radix=?, x) => {
 }
 
 external mod: (int, int) => int = "%modint"
+
+type rangeOptions = {step?: int, inclusive?: bool}
+let rangeWithOptions = (start, end, options) => {
+  let isInverted = start > end
+
+  let step = switch options.step {
+  | None => isInverted ? -1 : 1
+  | Some(0) if start !== end =>
+    Core__Error.raise(Core__Error.RangeError.make("Incorrect range arguments"))
+  | Some(n) => n
+  }
+
+  let length = if isInverted === (step >= 0) {
+    0 // infinite because step goes in opposite direction of end
+  } else if step == 0 {
+    options.inclusive === Some(true) ? 1 : 0
+  } else {
+    let range = isInverted ? start - end : end - start
+    let range = options.inclusive === Some(true) ? range + 1 : range
+    ceil(float(range) /. float(abs(step)))->Core__Float.toInt
+  }
+
+  Core__Array.fromInitializer(~length, i => start + i * step)
+}
+
+let range = (start, end) => rangeWithOptions(start, end, {})

src/Core__Int.resi

@@ -268,3 +268,57 @@ Int.mod(7, 4) == 3
 ```
 */
 external mod: (int, int) => int = "%modint"
+
+/**
+`range(start, end)` returns an int array of the sequence of integeres in the
+range `[start, end)`. That is, including `start` but excluding `end`.
+
+If `start < end` the sequence will be increasing in steps of 1.
+
+If `start < end` the sequence will be decreasing in steps of -1.
+
+This is equivalent to `rangeWithOptions` with `inclusive` set to `false` and
+`step` set to `1` if `start < end` and `-1` otherwise.
+
+## Examples
+
+```rescript
+Int.range(3, 6) == [3, 4, 5]
+Int.range(-3, -1) == [-3, -2]
+Int.range(3, 1) == [3, 2]
+```
+*/
+let range: (int, int) => array<int>
+
+/**
+The options for `rangeWithOptions`.
+*/
+type rangeOptions = {step?: int, inclusive?: bool}
+
+/**
+`rangeWithOptions(start, end, options)` is like `range`, but with `step` and
+`inlusive` options configurable.
+
+If `step` is set, the sequence will increase or decrease by that amount for each
+step. If `start < end` and `step` is negative, or vice versa, an empty array is
+returned since the sequence would otherwise never reach or exceed the end value
+and hence be infinite. If `step` is `0` and `start !=` end, a `RangeError` is
+raised as the sequence would never reach or exceed the end value and hence be
+infinite.
+
+If `inclusive` is set to `true`, the sequence will include `end` if `step` is
+set such that the sequence includes it.
+
+## Examples
+
+```rescript
+Int.rangeWithOptions(3, 7, {step: 2}) == [3, 5]
+Int.rangeWithOptions(3, 7, {step: 2, inclusive: true}) == [3, 5, 7]
+Int.rangeWithOptions(3, 6, {step: -2}) // RangeError
+```
+
+## Exceptions
+
+- Raises `RangeError` if `step == 0 && start != end`.
+*/
+let rangeWithOptions: (int, int, rangeOptions) => array<int>