CVS: smlnj notes,1.1.2.8,1.1.2.9

Update of /cvsroot/smlnj/smlnj
In directory sc8-pr-cvs1.sourceforge.net:/tmp/cvs-serv7681

Modified Files:
      Tag: primop-branch
	notes 
Log Message:
minor edits

Index: notes
===================================================================
RCS file: /cvsroot/smlnj/smlnj/Attic/notes,v
retrieving revision 1.1.2.8
retrieving revision 1.1.2.9
diff -C2 -d -r1.1.2.8 -r1.1.2.9
*** notes	26 Jul 2004 19:48:45 -0000	1.1.2.8
--- notes	27 Apr 2005 22:30:45 -0000	1.1.2.9
***************
*** 1,2 ****
--- 1,8 ----
+ These notes are my attempt to figure out what appears to be a very kludgy
+ treatement of how primops interact with the type checker.  I want to define
+ what the basic problem is, understand what the current code is doing to deal
+ with the problem, and then either eliminate the problem or find a more elegant
+ solution.
+ 
  1. PrimOp dependency in type checker
  
***************
*** 41,55 ****
  compatible.
  
! eqvTnspTy (mnemonic for what?) creates a generic instantiation of the actual
! type (actInst, with generic meta-tyvars actInstTvs), a separate generic
! instantiation (specInst, specInstTvs) of the specty type, which may be less polymorphic
! than actualty, and then unifies actInst and specInst.  This unification may
! cause tyvars in actInstTvs to be instantiated.  Then specInstTvs is transformed
! by TU.tyvarType to produce the second result, boundTvs.
  
! TU.tyvarType turns type expressions that representing meta type
! variables into the tyvars that they contain, stripping off VARtys and 
! following instantiations.  Note that instantiatePoly returns a list of
! type _expressions_ (VARty's) as its second result.
  
      fun eqvTnspTy (specty: ty, actualty: ty) : (ty * tyvar list) = 
--- 47,62 ----
  compatible.
  
! eqvTnspTy (mnemonic for what?) creates a generic instantiation of the
! actual type (actInst, with generic meta-tyvars actInstTvs), a separate
! generic instantiation (specInst, specInstTvs) of the specty type,
! which may be less polymorphic than actualty, and then unifies actInst
! and specInst.  This unification may cause tyvars in actInstTvs to be
! instantiated.  Then specInstTvs is transformed by TU.tyvarType to
! produce the second result, boundTvs.
  
! TU.tyvarType turns type expressions that represent meta type variables
! into the tyvars that they contain, stripping off VARtys and following
! instantiations.  Note that instantiatePoly returns a list of type
! _expressions_ (VARty's) as its second result.
  
      fun eqvTnspTy (specty: ty, actualty: ty) : (ty * tyvar list) = 
***************
*** 63,80 ****
        end
  
! The unification will cause some tyvars in actInstTvs to be instantiated
! to non-type-variable type terms (subterms of specInst), where specty is more
! specific than actualty). Where corresponding subterms are both type variables,
! the specty tyvar (a member of specInstTvs) will be instantiated to the
! corresponding actualty type variable (a member of actInstTvs) because of the
! right-to-left instantiation bias in Unify/unifyTyvars [Elaborator/types/unify.sml].
  
! So the resultant type term actInst may contain (uninstantiated) tyvars in specInstTvs
! as well as some (uninstantiated) tyvars in actInstTvs.  For the latter tyvars,
! the matching tyvar in specInstTvs will have been instantiated to it.  So the
! specInstTvs will contain all the tyvars occuring in actInst, some of which will
! be uninstantiated, while others will be instantiated to tyvars in actInstTvs.
! Applying TU.tyvarType will strip off the instantiations, so that the resulting
! boundtvs will contain a mixture of the tyvars from actInstTvs and specInstTvs.
  
  Example:
--- 70,90 ----
        end
  
! The unification will cause some tyvars in actInstTvs to be
! instantiated to non-type-variable type terms (subterms of specInst),
! where specty is more specific than actualty). Where corresponding
! subterms are both type variables, the specty tyvar (a member of
! specInstTvs) will be instantiated to the corresponding actualty type
! variable (a member of actInstTvs) because of the right-to-left
! instantiation bias in Unify/unifyTyvars [Elaborator/types/unify.sml].
  
! So the resultant type term actInst may contain (uninstantiated) tyvars
! in specInstTvs as well as some (uninstantiated) tyvars in actInstTvs.
! For the latter tyvars, the matching tyvar in specInstTvs will have
! been instantiated to it.  So the specInstTvs will contain all the
! tyvars occuring in actInst, some of which will be uninstantiated,
! while others will be instantiated to tyvars in actInstTvs.  Applying
! TU.tyvarType will strip off the instantiations, so that the resulting
! boundtvs will contain a mixture of the tyvars from actInstTvs and
! specInstTvs.
  
  Example:



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