Changes between Version 13 and Version 14 of PolymorphicComponents

Timestamp:

01/19/07 16:03:18 (6 years ago)

Author:

ijones

Comment:

--

PolymorphicComponents

@@ -40 +40 @@
 }}}
  1. hugs vs. ghc treatment as keyword (see below)
- 1. design choice: only wildcard & variables required in patterns (ghc allows as-patterns, hugs doesn't) allowed for polymorphic fields
+ 1. design choice: only wildcard & variables are allowed when pattern matching on polymorphic components (ghc allows as-patterns, hugs doesn't)
 
 == Tickets ==
@@ -77 +77 @@
         | C2 { x :: forall a. (Eq a,Show a) => a -> a } 
 }}}
- 1. ''note'' when you pattern-match on a field w/ a polymorphic type, the bound variables also have a polymorphic type
-   1. but case is different; it instantiates the forall to a monomorphic type as below:
+ 1. ''note'' you can name polymorphic components (see design choice above)
+   1. when you match on ''x'' it instantiates the forall to a monomorphic type as below:
 {{{
 data S    = C (forall a. [a])
@@ -90 +90 @@
 f (C []) = True
 }}}
+   1. desugaring...
+{{{
+f (C []) = e1 -- illegal
+}}}
+  would desugar to
+{{{
+f x = case x of
+       C [] -> e 1 -- illegal
+       _ -> error ...
+}}}
+  would desugar to 
+{{{
+case x of
+ C y -> case y of -- NOT illegal
+         [] -> e1
+         _ -> error...
+ _ -> error...
+
+}}}
+  which is a little funny.
+ 1. where is explanation of type checking...
+ 1. where to put the bangs in strict polymorphic fields, hugs and GHC differ - can't figure it out in Hugs