Changes between Version 1 and Version 2 of TFvsFD

Timestamp:

06/05/12 11:04:29 (12 months ago)

Author:

atnnn

Comment:

--

TFvsFD

@@ -70 +70 @@
 }}}
 
-But type families cannot be partially applied (`Type synonym F' should
-have 1 argument, but has been given none`):
+But type families cannot be partially applied ({{{Type synonym F' should have 1 argument, but has been given none}}}):
 
 {{{
@@ -84 +83 @@
 
 Type synonyms can manipulate constraint kinds but can not use
-them. The following code doesn't make sense.
+them. The standard encoding of the above class from FD to
+superclass equalities does not work.
 
 {{{
 class (f :<$>: a) ~ b =>  FMap (f :: * -> * -> Constraint) a b
   where type f :<$>: a
-instance FMap f (HJust a) b
-  where type f :<$>: (HJust a) = f a b => b
+instance f a b => FMap f (HJust a) b
+  where type f :<$>: (HJust a) = HJust b
 }}}
 
@@ -255 +255 @@
 ==== The result of a class constraint is not obvious. ====
 
-`C a b` could have
- the FD `a -> b`, `b -> a`, neither, both or even someting like
+`C a b` could have the FD `a -> b`, `b -> a`, neither, both or even someting like
 `-> a b`. Looking at the `:info` doesn't always help to figure out the
 resulting FD of a class. The kind of a class does not include the