[project @ 2000-10-03 08:43:00 by simonpj]

--------------------------------------
	Adding generics		SLPJ Oct 2000
	--------------------------------------

This big commit adds Hinze/PJ-style generic class definitions, based
on work by Andrei Serjantov.  For example:

  class Bin a where
    toBin   :: a -> [Int]
    fromBin :: [Int] -> (a, [Int])

    toBin {| Unit |}    Unit	  = []
    toBin {| a :+: b |} (Inl x)   = 0 : toBin x
    toBin {| a :+: b |} (Inr y)   = 1 : toBin y
    toBin {| a :*: b |} (x :*: y) = toBin x ++ toBin y


    fromBin {| Unit |}    bs      = (Unit, bs)
    fromBin {| a :+: b |} (0:bs)  = (Inl x, bs')    where (x,bs') = fromBin bs
    fromBin {| a :+: b |} (1:bs)  = (Inr y, bs')    where (y,bs') = fromBin bs
    fromBin {| a :*: b |} bs  	  = (x :*: y, bs'') where (x,bs' ) = fromBin bs
							  (y,bs'') = fromBin bs'

Now we can say simply

  instance Bin a => Bin [a]

and the compiler will derive the appropriate code automatically.

		(About 9k lines of diffs.  Ha!)


Generic related things
~~~~~~~~~~~~~~~~~~~~~~

* basicTypes/BasicTypes: The EP type (embedding-projection pairs)

* types/TyCon:
	An extra field in an algebraic tycon (genInfo)

* types/Class, and hsSyn/HsBinds:
	Each class op (or ClassOpSig) carries information about whether
	it  	a) has no default method
		b) has a polymorphic default method
		c) has a generic default method
	There's a new data type for this: Class.DefMeth

* types/Generics:
	A new module containing good chunk of the generic-related code
	It has a .hi-boot file (alas).

* typecheck/TcInstDcls, typecheck/TcClassDcl:
	Most of the rest of the generics-related code

* hsSyn/HsTypes:
	New infix type form to allow types of the form
		data a :+: b = Inl a | Inr b

* parser/Parser.y, Lex.lhs, rename/ParseIface.y:
	Deal with the new syntax

* prelude/TysPrim, TysWiredIn:
	Need to generate generic stuff for the wired-in TyCons

* rename/RnSource RnBinds:
	A rather gruesome hack to deal with scoping of type variables
	from a generic patterns.  Details commented in the ClassDecl
	case of RnSource.rnDecl.

	Of course, there are many minor renamer consequences of the
	other changes above.

* lib/std/PrelBase.lhs
	Data type declarations for Unit, :+:, :*:


Slightly unrelated housekeeping
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
* hsSyn/HsDecls:
	ClassDecls now carry the Names for their implied declarations
	(superclass selectors, tycon, etc) in a list, rather than
	laid out one by one.  This simplifies code between the parser
	and the type checker.

* prelude/PrelNames, TysWiredIn:
	All the RdrNames are now together in PrelNames.

* utils/ListSetOps:
	Add finite mappings based on equality and association lists (Assoc a b)
	Move stuff from List.lhs that is related

1 files changed, 13 insertions, 7 deletions

diff --git a/ghc/compiler/hsSyn/HsBinds.lhs b/ghc/compiler/hsSyn/HsBinds.lhs
index 894a6321ab..b33ab92ba2 100644
--- a/ghc/compiler/hsSyn/HsBinds.lhs
+++ b/ghc/compiler/hsSyn/HsBinds.lhs
@@ -25,6 +25,7 @@ import BasicTypes	( RecFlag(..), Fixity )
 import Outputable	
 import SrcLoc		( SrcLoc )
 import Var		( TyVar )
+import Class            ( DefMeth (..) )
 \end{code}
 
 %************************************************************************
@@ -236,11 +237,9 @@ data Sig name
 		(HsType name)
 		SrcLoc
 
-  | ClassOpSig	name		-- Selector name
-		(Maybe 		-- Nothing for source-file class signatures
-		      (name,		-- Default-method name (if any)
-		       Bool))		-- True <=> there is an explicit, programmer-supplied
-					-- 	    default declaration in the class decl
+  | ClassOpSig	name			-- Selector name
+                (Maybe (DefMeth name))	-- Nothing for source-file class signatures
+					-- Gives DefMeth info for interface files sigs
 		(HsType name)
 		SrcLoc
 
@@ -338,8 +337,15 @@ ppr_sig (ClassOpSig var dm ty _)
       = sep [ppr var <+> pp_dm <+> dcolon, nest 4 (ppr ty)]
       where
 	pp_dm = case dm of 
-		  Just (_, True) -> equals 	-- Default-method indicator
-		  other		 -> empty
+		  Just (DefMeth _) -> equals 	-- Default method indicator
+		  Just GenDefMeth  -> semi      -- Generic method indicator
+		  Just NoDefMeth   -> empty     -- No Method at all
+		  -- Not convinced this is right...
+		  -- Not used in interface file output hopefully
+		  -- but needed for ddump-rn ??
+		  other		   -> dot
+				   -- empty     -- No method at all
+
 
 ppr_sig (SpecSig var ty _)
       = sep [ hsep [text "{-# SPECIALIZE", ppr var, dcolon],