Comments

Author: natefaubion

src/Control/Monad/Eff/AVar.js

@@ -260,11 +260,9 @@ function drainVar (left, right, avar) {
         if (p = takeHead(ps)) {
           runEff(p.cb(value));
         }
-
         while (r = takeHead(rs)) {
           runEff(r(value));
         }
-
         if (t = takeHead(ts)) {
           runEff(t(value));
         }

src/Control/Monad/Eff/AVar.purs

@@ -30,30 +30,52 @@ foreign import data AVar ∷ Type → Type
 
 foreign import data AVAR ∷ Effect
 
+-- | Creates a fresh AVar.
 foreign import makeEmptyVar ∷ ∀ eff a. AVarEff eff (AVar a)
 
+-- | Creates a fresh AVar with an initial value.
 foreign import makeVar ∷ ∀ eff a. a → AVarEff eff (AVar a)
 
+-- | Synchronously checks whether an AVar currently has a value.
 foreign import isEmptyVar ∷ ∀ eff a. AVar a → AVarEff eff Boolean
 
+-- | Kills the AVar with an exception. All pending and future actions will
+-- | resolve immediately with the provided exception.
 killVar ∷ ∀ eff a. AVar a → Error → AVarEff eff Unit
 killVar avar err = Fn.runFn4 _killVar Left Right avar err
 
+-- | Sets the value of the AVar. If the AVar is already filled, it will be
+-- | queued until the value is emptied. Multiple puts will resolve in order as
+-- | the AVar becomes available. Returns an effect which will remove the
+-- | callback from the pending queue.
 putVar ∷ ∀ eff a. AVar a → a → AVarCallback eff Unit → AVarEff eff (AVarEff eff Unit)
 putVar avar value cb = Fn.runFn5 _putVar Left Right avar value cb
 
+-- | Attempts to synchronously fill an AVar. If the AVar is already filled,
+-- | this will do nothing. Returns true or false depending on if it succeeded.
 tryPutVar ∷ ∀ eff a. AVar a → a → AVarEff eff Boolean
 tryPutVar avar value = Fn.runFn4 _tryPutVar Left Right avar value
 
+-- | Takes the AVar value, leaving it empty. If the AVar is already empty,
+-- | the callback will be queued until the AVar is filled. Multiple takes will
+-- | resolve in order as the AVar fills. Returns an effect which will remove
+-- | the callback from the pending queue.
 takeVar ∷ ∀ eff a. AVar a → AVarCallback eff a → AVarEff eff (AVarEff eff Unit)
 takeVar avar cb = Fn.runFn4 _takeVar Left Right avar cb
 
+-- | Attempts to synchronously take an AVar value, leaving it empty. If the
+-- | AVar is empty, this will return `Nothing`.
 tryTakeVar ∷ ∀ eff a. AVar a → AVarEff eff (Maybe a)
 tryTakeVar avar = Fn.runFn5 _tryTakeVar Left Right Nothing Just avar
 
+-- | Reads the AVar value. Unlike `takeVar`, this will not leave the AVar empty.
+-- | If the AVar is empty, this will queue until it is filled. Multiple reads
+-- | will resolve at the same time, as soon as possible.
 readVar ∷ ∀ eff a. AVar a → AVarCallback eff a → AVarEff eff (AVarEff eff Unit)
 readVar avar cb = Fn.runFn4 _readVar Left Right avar cb
 
+-- | Attempts to synchronously read an AVar. If the AVar is empty, this will
+-- | return `Nothing`.
 tryReadVar ∷ ∀ eff a. AVar a → AVarEff eff (Maybe a)
 tryReadVar avar = Fn.runFn3 _tryReadVar Nothing Just avar
 

test/Main.purs

@@ -169,6 +169,7 @@ test_cancel = test "cancel" do
   c1 ← putVar v1 "a" $ traverse_ \_ → modifyRef ref (_ <> "a")
   c2 ← putVar v1 "b" $ traverse_ \_ → modifyRef ref (_ <> "b")
   c3 ← putVar v1 "c" $ traverse_ \_ → modifyRef ref (_ <> "c")
+  c1
   c2
   _  ← tryTakeVar v1
   _  ← tryTakeVar v1
@@ -186,8 +187,9 @@ test_cancel = test "cancel" do
   c8 ← readVar v3 $ traverse_ \_ → modifyRef ref (_ <> "h")
   c9 ← readVar v3 $ traverse_ \_ → modifyRef ref (_ <> "i")
   c8
+  c9
   _  ← tryPutVar v3 "a"
-  eq "acdfgi" <$> readRef ref
+  eq "cdfg" <$> readRef ref
 
 main ∷ TestEff Unit
 main = do