diff: clpr/cfloat.m minor style improvements

[Fergus Henderson]

clpr/cfloat.m:
	Rename the cfloat "trail" as the cfloat "choicepoint stack",
	since the latter more accurately reflects its purpose.

Index: cfloat.m
===================================================================
RCS file: /home/staff/zs/imp/clpr/cfloat.m,v
retrieving revision 1.1
diff -u -u -r1.1 cfloat.m
--- 1.1	1997/08/27 17:11:05
+++ cfloat.m	1997/09/01 08:20:28
@@ -312,42 +312,41 @@
 #endif
 
 /*
-** There are three trails:
+** There are three data structures involved in trailing:
 **	- the Mercury trail
-**	- the cfloat.m trail-info free list
+**	- the cfloat.m choice point stack
 **	- the CLP(R) trail
 ** The Mercury trail contains function trail entries which point to
-** the cfloat.m trail.  (The reason why those two are separate is modularity.)
-** The cfloat.m trail is organized as a doubly-linked list.
-** The cfloat.m trail entries store the CLP(R) global variables, including
+** the cfloat.m choice point stack.
+** The cfloat.m choice point stack is represented a doubly-linked list.
+** Its entries store the values of the CLP(R) global variables, including
 ** the `trtop' variable, which points to the top of the CLP(R) trail.
 */
-/* XXX rename as `choicepoint' */
-typedef struct ML_cfloat_trail_entry {
+typedef struct ML_cfloat_choicepoint {
 	int stamp;
 	int slack_id;
 	int solver_id;
 	int trtop;
-	struct ML_cfloat_trail_entry *prev;
-	struct ML_cfloat_trail_entry *next;
-} ML_cfloat_trail_entry;
+	struct ML_cfloat_choicepoint *prev;
+	struct ML_cfloat_choicepoint *next;
+} ML_cfloat_choicepoint;
 
-ML_cfloat_trail_entry ML_cfloat_first_trail_entry;
-ML_cfloat_trail_entry * ML_cfloat_trail_ptr = &ML_cfloat_first_trail_entry;
+ML_cfloat_choicepoint ML_cfloat_first_choicepoint;
+ML_cfloat_choicepoint * ML_cfloat_current_cp = &ML_cfloat_first_choicepoint;
 
 /* XXX efficiency could be improved -- we should use a free list here */
 
-#define ML_cfloat_next_trail_entry()					\
-	( ML_cfloat_trail_ptr->next == NULL ?				\
-		(ML_cfloat_trail_ptr->next = make(ML_cfloat_trail_entry), \
-		ML_cfloat_trail_ptr->next->next = NULL,			\
-		ML_cfloat_trail_ptr->next->prev = ML_cfloat_trail_ptr,	\
-		ML_cfloat_trail_ptr = ML_cfloat_trail_ptr->next)	\
+#define ML_cfloat_next_choicepoint()					\
+	( ML_cfloat_current_cp->next == NULL ?				\
+		(ML_cfloat_current_cp->next = make(ML_cfloat_choicepoint), \
+		ML_cfloat_current_cp->next->next = NULL,		\
+		ML_cfloat_current_cp->next->prev = ML_cfloat_current_cp,\
+		ML_cfloat_current_cp = ML_cfloat_current_cp->next)	\
 	:								\
-		(ML_cfloat_trail_ptr = ML_cfloat_trail_ptr->next)	\
+		(ML_cfloat_current_cp = ML_cfloat_current_cp->next)	\
 	)
-#define ML_cfloat_prev_trail_entry() \
-	(ML_cfloat_trail_ptr = ML_cfloat_trail_ptr->prev)
+#define ML_cfloat_prev_choicepoint() \
+	(ML_cfloat_current_cp = ML_cfloat_current_cp->prev)
 		
 #define ML_cfloat_maybe_trail_solver()				\
 	do {							\
@@ -366,27 +365,27 @@
 :- pragma(c_code, "
 
 void ML_cfloat_trail_solver(void) {
-	ML_cfloat_trail_entry *trail_entry = ML_cfloat_next_trail_entry();
-	trail_entry->stamp = stamp;
-	trail_entry->slack_id = slack_id;
-	trail_entry->solver_id = solver_id;
-	trail_entry->trtop = trtop;
-	MR_trail_function(ML_cfloat_untrail_func, (Word) trail_entry);
+	ML_cfloat_choicepoint *choicepoint = ML_cfloat_next_choicepoint();
+	choicepoint->stamp = stamp;
+	choicepoint->slack_id = slack_id;
+	choicepoint->solver_id = solver_id;
+	choicepoint->trtop = trtop;
+	MR_trail_function(ML_cfloat_untrail_func, (Word) choicepoint);
 	stamp = MR_current_choicepoint_id();
 }
 
 void ML_cfloat_untrail_func(Word datum, MR_untrail_reason reason) {
-	ML_cfloat_trail_entry *trail_entry = (ML_cfloat_trail_entry *) datum;
+	ML_cfloat_choicepoint *choicepoint = (ML_cfloat_choicepoint *) datum;
 	switch (reason) {
 		case MR_undo:
 		case MR_exception:
 		{
 			int old_trtop, i;
 
-			stamp = trail_entry->stamp;
-			slack_id = trail_entry->slack_id;
-			solver_id = trail_entry->solver_id;
-			old_trtop = trail_entry->trtop;
+			stamp = choicepoint->stamp;
+			slack_id = choicepoint->slack_id;
+			solver_id = choicepoint->solver_id;
+			old_trtop = choicepoint->trtop;
 			for (i = trtop - 1; i >= old_trtop; i--) {
 				solver_backtrack((Word) trail[i]);
 			}
@@ -394,7 +393,7 @@
 			break;
 		}
 		case MR_commit:
-			stamp = trail_entry->stamp;
+			stamp = choicepoint->stamp;
 			if (nlin_count != 0) {
 				fprintf(stderr, ""cfloat.m: warning: ""
 					""non-linear goals delayed, ""
@@ -404,7 +403,7 @@
 		default:
 			fatal_error(""cfloat.m: unknown MR_untrail_reason"");
 	}
-	ML_cfloat_prev_trail_entry();
+	ML_cfloat_prev_choicepoint();
 }
 ").
 

-- 
Fergus Henderson <fjh at cs.mu.oz.au>   |  "I have always known that the pursuit
WWW: <http://www.cs.mu.oz.au/~fjh>   |  of excellence is a lethal habit"
PGP: finger fjh at 128.250.37.3         |     -- the last words of T. S. Garp.