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Merged
merged 1 commit into from
Jun 13, 2014
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Use unit #1

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4 changes: 2 additions & 2 deletions README.md
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Expand Up @@ -11,13 +11,13 @@

### Values

modifyRef :: forall s r. RefVal s -> (s -> s) -> Eff (ref :: Ref | r) { }
modifyRef :: forall s r. RefVal s -> (s -> s) -> Eff (ref :: Ref | r) Unit

newRef :: forall s r. s -> Eff (ref :: Ref | r) (RefVal s)

readRef :: forall s r. RefVal s -> Eff (ref :: Ref | r) s

writeRef :: forall s r. RefVal s -> s -> Eff (ref :: Ref | r) { }
writeRef :: forall s r. RefVal s -> s -> Eff (ref :: Ref | r) Unit


## Module Control.Monad.Eff.Ref.Unsafe
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4 changes: 2 additions & 2 deletions src/Control/Monad/Eff/Ref.purs
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Expand Up @@ -29,7 +29,7 @@ foreign import modifyRef
\ return {};\
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@paf31 paf31 Jun 13, 2014

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One very slight issue here: these various FFI calls return {}, which doesn't have the runtime representation of the type Unit, so pattern matching on the result, for example, while not necessarily useful, could result in a runtime error. To be super safe, these things should probably return Prelude.unit.

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@garyb garyb Jun 13, 2014

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Yeah, I did have a slight worry about that. I checked the generated code for Eq, Ord, things like that and none of them attempt to read from the value so I think at least in PS code it should be fine. I also figure this'll be fixed when we get newtypes working.

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@garyb garyb Jun 14, 2014

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Ok, so this is a problem actually when compiled with no optimizations. One fix is to not pattern match in the Prelude definitions, just use _ instead of (Unit {}). I've updated the Prelude in ps-in-ps to have the definitions this way so it's not broken in psci.

\ };\
\ };\
\}" :: forall s r. RefVal s -> (s -> s) -> Eff (ref :: Ref | r) {}
\}" :: forall s r. RefVal s -> (s -> s) -> Eff (ref :: Ref | r) Unit

foreign import writeRef
"function writeRef(ref) {\
Expand All @@ -39,4 +39,4 @@ foreign import writeRef
\ return {};\
\ };\
\ };\
\}" :: forall s r. RefVal s -> s -> Eff (ref :: Ref | r) {}
\}" :: forall s r. RefVal s -> s -> Eff (ref :: Ref | r) Unit