Avoid RangeError in arrayBind foreign implementation

CHANGELOG.md

@@ -9,6 +9,7 @@ Breaking changes:
 New features:
 
 Bugfixes:
+- Avoid `RangeError` in `arrayBind` foreign implementation (#314 by @pete-murphy)
 
 Other improvements:
 

src/Control/Bind.js

@@ -1,8 +1,17 @@
 export const arrayBind = function (arr) {
+  if (typeof Array.prototype.flatMap === "function") {
+    return function (f) {
+      return arr.flatMap(f);
+    };
+  }
+
   return function (f) {
-    var result = [];
-    for (var i = 0, l = arr.length; i < l; i++) {
-      Array.prototype.push.apply(result, f(arr[i]));
+    const result = [];
+    for (let i = 0, l = arr.length; i < l; i++) {
+      const xs = f(arr[i]);
+      for (let j = 0, m = xs.length; j < m; j++) {
+        result.push(xs[j]);
+      }
     }
     return result;
   };

test/Test/Main.js

@@ -40,3 +40,11 @@ export function testNumberShow(showNumber) {
     ]);
   };
 }
+
+export function makeArray(length) {
+  var arr = [];
+  for (var i = 0; i < length; i++) {
+    arr.push(i);
+  }
+  return arr;
+}

test/Test/Main.purs

@@ -22,6 +22,7 @@ main = do
     testReflectType
     testReifyType
     testSignum
+    testArrayBind
 
 foreign import testNumberShow :: (Number -> String) -> AlmostEff
 
@@ -189,3 +190,14 @@ testSignum = do
   assert "signum positive zero" $ show (1.0/(signum 0.0)) == "Infinity"
   assert "Clarifies what 'signum negative zero' test is doing" $ show (1.0/(-0.0)) == "-Infinity"
   assert "signum negative zero" $ show (1.0/(signum (-0.0))) == "-Infinity"
+
+foreign import makeArray :: Int -> Array Int
+
+testArrayBind :: AlmostEff
+testArrayBind = do
+  assert "Array bind does not cause RangeError" do
+    let
+      _ = do
+        _ <- [unit]
+        makeArray 106_000
+    true