prevent runtime error for partial functions for ST arrays (#111)

* prevent runtime error for partial functions for ST arrays

* add Data.Array.ST.Partial tests

Author: mhuisi

src/Data/Array/ST/Partial.js

@@ -1,14 +1,14 @@
 "use strict";
 
-exports.peekSTArray = function (xs) {
+exports.peekSTArrayImpl = function (xs) {
   return function (i) {
     return function () {
       return xs[i];
     };
   };
 };
 
-exports.pokeSTArray = function (xs) {
+exports.pokeSTArrayImpl = function (xs) {
   return function (i) {
     return function (a) {
       return function () {

src/Data/Array/ST/Partial.purs

@@ -13,18 +13,33 @@ import Data.Array.ST (STArray)
 import Data.Unit (Unit)
 
 -- | Read the value at the specified index in a mutable array.
-foreign import peekSTArray
+peekSTArray
   :: forall a h r
    . Partial
   => STArray h a
   -> Int
   -> Eff (st :: ST h | r) a
+peekSTArray = peekSTArrayImpl
+
+foreign import peekSTArrayImpl
+  :: forall a h r
+   . STArray h a
+  -> Int
+  -> Eff (st :: ST h | r) a
 
 -- | Change the value at the specified index in a mutable array.
-foreign import pokeSTArray
+pokeSTArray
   :: forall a h r
    . Partial
   => STArray h a
   -> Int
   -> a
   -> Eff (st :: ST h | r) Unit
+pokeSTArray = pokeSTArrayImpl
+
+foreign import pokeSTArrayImpl
+  :: forall a h r
+   . STArray h a
+  -> Int
+  -> a
+  -> Eff (st :: ST h | r) Unit

test/Test/Data/Array/ST/Partial.purs

@@ -0,0 +1,28 @@
+module Test.Data.Array.ST.Partial (testArraySTPartial) where
+
+import Prelude
+
+import Control.Monad.Eff (Eff)
+import Control.Monad.Eff.Console (log, CONSOLE)
+import Control.Monad.ST (pureST)
+
+import Data.Array.ST (thaw, unsafeFreeze)
+import Data.Array.ST.Partial (peekSTArray, pokeSTArray)
+
+import Partial.Unsafe (unsafePartial)
+
+import Test.Assert (assert, ASSERT)
+
+testArraySTPartial :: forall eff. Eff (console :: CONSOLE, assert :: ASSERT | eff) Unit
+testArraySTPartial = do
+
+  log "peekSTArray should return the value at the specified index"
+  assert $ 2 == pureST do
+    a <- thaw [1, 2, 3]
+    unsafePartial $ peekSTArray a 1
+
+  log "pokeSTArray should modify the value at the specified index"
+  assert $ [1, 4, 3] == pureST do
+    a <- thaw [1, 2, 3]
+    unsafePartial $ pokeSTArray a 1 4
+    unsafeFreeze a

test/Test/Main.purs

@@ -9,9 +9,11 @@ import Test.Assert (ASSERT)
 import Test.Data.Array (testArray)
 import Test.Data.Array.Partial (testArrayPartial)
 import Test.Data.Array.ST (testArrayST)
+import Test.Data.Array.ST.Partial (testArraySTPartial)
 
 main :: forall eff. Eff (console :: CONSOLE, assert :: ASSERT | eff) Unit
 main = do
   testArray
   testArrayST
   testArrayPartial
+  testArraySTPartial