add second form of poll with timeout, use as MVar.wait millis

Frege · Feb 22, 2019 · f6f66bb · f6f66bb
1 parent 847e560
commit f6f66bb
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Showing 2 changed files with 15 additions and 2 deletions.
diff --git a/frege/control/Concurrent.fr b/frege/control/Concurrent.fr
@@ -34,7 +34,10 @@ abstract newtype MVar a  =  MV (MutableIO (BlockingQueue a)) where
     offer (MV q) a  = q.offer a
 
     --- get the value from a 'MVar', return 'Nothing' when empty
-    poll  (MV q)    = q.poll  
+    poll  (MV q)    = q.poll
+
+    --- like 'poll', but waits a specified number of milliseconds for a value to become available
+    wait  (MV q) n  = q.poll n TimeUnit.milliSeconds   
 
 -- Haskell compatibility
 newEmptyMVar    = MVar.newEmpty

diff --git a/frege/java/util/Concurrent.fr b/frege/java/util/Concurrent.fr
@@ -8,6 +8,8 @@ import Java.Util
 data RejectedExecutionException = pure native java.util.concurrent.RejectedExecutionException
 derive Exceptional RejectedExecutionException
 
+data TimeUnit = pure native java.util.concurrent.TimeUnit where
+    pure native milliSeconds java.util.concurrent.TimeUnit.MILLISECONDS :: TimeUnit
 
 data BlockingQueue e = native java.util.concurrent.BlockingQueue where
     --- add element to blocking queue, throw exception if not possible
@@ -19,8 +21,16 @@ data BlockingQueue e = native java.util.concurrent.BlockingQueue where
 
     --- get and remove element from blocking queue, throw exception if it is empty
     native remove   :: MutableIO (BlockingQueue e) -> IO e throws NoSuchElementException
-    --- get and remove element from blocking queue, return null if it is empty
+    {-- 
+        1. Get and remove element from blocking queue, return null if it is empty.
+        
+        2. Get and removes element of this queue, waiting up to the specified wait time if necessary for an element to become available.
+        Return null if nothing becomes available.
+        
+    --}
+
     native poll     :: MutableIO (BlockingQueue e) -> IO (Maybe e)
+                     | MutableIO (BlockingQueue e) -> Int -> TimeUnit -> IO (Maybe e) throws InterruptedException
     --- get and remove element from blocking queue, block until something is available
     native take     :: MutableIO (BlockingQueue e) -> IO e throws InterruptedException