Add clone to Data.Array.ST

src/Data/Array/ST.js

@@ -53,6 +53,8 @@ export const freezeImpl = copyImpl;
 
 export const thawImpl = copyImpl;
 
+export const cloneImpl = copyImpl;
+
 export const sortByImpl = (function () {
   function mergeFromTo(compare, fromOrdering, xs1, xs2, from, to) {
     var mid;

src/Data/Array/ST.purs

@@ -24,6 +24,7 @@ module Data.Array.ST
   , sortWith
   , freeze
   , thaw
+  , clone
   , unsafeFreeze
   , unsafeThaw
   , toAssocArray
@@ -95,6 +96,15 @@ thaw = runSTFn1 thawImpl
 -- | Create a mutable copy of an immutable array.
 foreign import thawImpl :: forall h a. STFn1 (Array a) h (STArray h a)
 
+-- | Make a mutable copy of a mutable array.
+clone
+  :: forall h a
+   . STArray h a
+  -> ST h (STArray h a)
+clone = runSTFn1 cloneImpl
+
+foreign import cloneImpl :: forall h a. STFn1 (STArray h a) h (STArray h a)
+
 -- | Sort a mutable array in place. Sorting is stable: the order of equal
 -- | elements is preserved.
 sort :: forall a h. Ord a => STArray h a -> ST h (STArray h a)

test/Test/Data/Array/ST.purs

@@ -45,6 +45,13 @@ testArrayST = do
     arr <- STA.thaw [1, 2, 3]
     STA.freeze arr) == [1, 2, 3]
 
+  log "clone should produce a shallow copy of an STArray"
+
+  assert $ ST.run (do
+    arr <- STA.thaw [1, 2, 3]
+    arr2 <- STA.clone arr
+    STA.freeze arr2) == [1, 2, 3]
+
   log "unsafeThaw should produce an STArray from a standard array"
 
   assert $ STA.run (STA.unsafeThaw [1, 2, 3]) == [1, 2, 3]