/* --------------------------------------------------------------------------
 * Definitions for substitution data structure and operations.
 *
 * The Hugs 98 system is Copyright (c) Mark P Jones, Alastair Reid, the
 * Yale Haskell Group, and the OGI School of Science & Engineering at OHSU,
 * 1994-2003, All rights reserved.  It is distributed as free software under
 * the license in the file "License", which is included in the distribution.
 *
 * ------------------------------------------------------------------------*/
#ifndef __SUBST_H__
#define __SUBST_H__

/* #define DEBUG_TYPES    1 */
/* #define DEBUG_KINDS    1 */
/* #define DEBUG_DEFAULTS 1 */
/* #define DEBUG_SELS     1 */
/* #define DEBUG_DEPENDS  1 */
/* #define DEBUG_DERIVING 1 */

typedef struct {			/* Each type variable contains:	   */
    Type bound;				/* A type skeleton (unbound==NIL)  */
    Int  offs;				/* Offset for skeleton		   */
    Kind kind;				/* kind annotation		   */
} Tyvar;

#if     FIXED_SUBST			/* storage for type variables	   */
extern	Tyvar		tyvars[];
#else
extern  Tyvar		*tyvars;	/* storage for type variables	   */
#endif
extern	Int		typeOff;	/* offset of result type 	   */
extern	Type		typeIs;		/* skeleton of result type	   */
extern  Int		typeFree;	/* freedom in instantiated type	   */
extern	List		predsAre;	/* list of predicates in type	   */
extern  List		genericVars;	/* list of generic vars		   */
extern  List		btyvars;	/* explicitly scoped type vars	   */

#define tyvar(n)	(tyvars+(n))	/* nth type variable		   */
#define tyvNum(t)	((t)-tyvars)	/* and the corresp. inverse funct. */
#define isBound(t)	(((t)->bound) && ((t)->bound!=SKOLEM))
#define aVar		mkOffset(0)	/* Simple skeletons for type vars  */
#define bVar		mkOffset(1)
#define enterBtyvs()	btyvars = cons(NIL,btyvars)
#define leaveBtyvs()	btyvars = tl(btyvars)

#define deRef(tyv,t,o)  while ((tyv=getTypeVar(t,o)) && isBound(tyv)) { \
			    t = tyv->bound;                             \
			    o = tyv->offs;                              \
			}

					/* offs values when isNull(bound): */
#define FIXED_TYVAR	0	        /* fixed in current assumption	   */
#define UNUSED_GENERIC	1	        /* not fixed, not yet encountered  */
#define GENERIC		2	        /* GENERIC+n==nth generic var found*/

extern  char		*unifyFails;	/* Unification error message	   */

extern Void  emptySubstitution	Args((Void));
extern Int   newTyvars		Args((Int));
#define      newKindvars(n)	newTyvars(n)
extern Int   newKindedVars	Args((Kind));
extern Void  instantiate	Args((Type));

extern Pair  findBtyvs		Args((Text));
extern Void  markBtyvs		Args((Void));
extern Type  localizeBtyvs	Args((Type));

extern Tyvar *getTypeVar	Args((Type,Int));
extern Void  tyvarType		Args((Int));
extern Void  bindTv		Args((Int,Type,Int));
extern Cell  getDerefHead	Args((Type,Int));
extern Void  expandSyn		Args((Tycon, Int, Type *, Int *));

extern Void  clearMarks		Args((Void));
extern Void  markAllVars	Args((Void));
extern Void  resetGenerics	Args((Void));
extern Void  markTyvar		Args((Int));
extern Void  markType		Args((Type,Int));
extern Void  markPred		Args((Cell));

extern Type  copyTyvar		Args((Int));
extern Type  copyType		Args((Type,Int));
extern Cell  copyPred		Args((Cell,Int));
extern Type  dropRank2		Args((Type,Int,Int));
extern Type  dropRank1		Args((Type,Int,Int));
extern Void  liftRank2Args	Args((List,Int,Int));
extern Type  liftRank2		Args((Type,Int,Int));
extern Type  liftRank1		Args((Type,Int,Int));
#if DEBUG_TYPES
extern Type  debugTyvar		Args((Int));
extern Type  debugType		Args((Type,Int));
extern List  debugContext	Args((List));
extern Cell  debugPred		Args((Cell,Int));
#endif
extern Kind  copyKindvar	Args((Int));
extern Kind  copyKind		Args((Kind,Int));

extern Bool  eqKind		Args((Kind,Kind));
extern Kind  getKind		Args((Cell,Int));

extern List  genvarTyvar	Args((Int,List));
extern List  genvarType		Args((Type,Int,List));

extern Bool  doesntOccurIn	Args((Tyvar*,Type,Int));
extern Bool  unify		Args((Type,Int,Type,Int));
extern Bool  kunify		Args((Kind,Int,Kind,Int));

extern Void  typeTuple		Args((Cell));
extern Kind  simpleKind		Args((Int));
extern Void  varKind		Args((Int));

extern Bool  samePred		Args((Cell,Int,Cell,Int));
extern Bool  matchPred		Args((Cell,Int,Cell,Int));
extern Bool  unifyPred		Args((Cell,Int,Cell,Int));
extern Inst  findInstFor	Args((Cell,Int));

extern Void  improve		Args((Int,List,List));
extern Void  improve1		Args((Int,List,Cell,Int));

extern Bool  sameSchemes	Args((Type,Type));
extern Bool  sameType		Args((Type,Int,Type,Int));
extern Bool  matchType		Args((Type,Int,Type,Int));

/*-------------------------------------------------------------------------*/

#endif /* __SUBST_H__ */