1 files changed, 75 insertions, 31 deletions

diff --git a/eval.c b/eval.c
index e0d7286..e42439f 100644
--- a/eval.c
+++ b/eval.c
@@ -6,10 +6,12 @@
 #include "fns.h"
 
 Goal *addgoals(Goal *, Term *);
+Predicate *findpredicate(Predicate *, Term *);
 Clause *findclause(Clause *, Term *, Binding **);
 int equalterms(Term *, Term *);
 Goal *copygoals(Goal *);
 Builtin findbuiltin(Term *);
+void addchoicepoints(Clause *, Term *, Goal *, Module *);
 
 static uvlong clausenr;
 
@@ -45,23 +47,17 @@ evalquery(Term *query, Binding **resultbindings)
 	}
 
 	while(goalstack->goal != nil){
-		Clause *startclause;
-		Term *goal;
-		Goal *oldgoalstack;
-
-		startclause = nil; /* Where to start looking for a matching clause. Used by backtracking */
-Retry:
-		goal = goalstack->goal;
-		oldgoalstack = goalstack;
+		Term *goal = goalstack->goal;
+		Term *catcher = goalstack->catcher;
 		goalstack = goalstack->next;
 
-		if(oldgoalstack->catcher)
+		if(catcher)
 			continue;
 
 		if(debug)
 			print("Working goal: %S\n", prettyprint(goal, 0, 0, 0));
 
-		if(startclause == nil && goal->tag == CompoundTerm && goal->arity == 2 && runestrcmp(goal->text, L":") == 0){
+		if(goal->tag == CompoundTerm && goal->arity == 2 && runestrcmp(goal->text, L":") == 0){
 			Term *module = goal->children;
 			if(module->tag == AtomTerm){
 				Module *m = getmodule(module->text);
@@ -70,16 +66,11 @@ Retry:
 				else{
 					goal = module->next;
 					currentmodule = m;
-					startclause = m->clauses;
-					oldgoalstack->goal = goal;
 				}
 			}else
 				goal = typeerror(L"module", module);
 		}
 
-		if(startclause == nil)
-			startclause = currentmodule->clauses;
-
 		Binding *bindings = nil;
 		Clause *clause = nil;
 		
@@ -90,20 +81,17 @@ Retry:
 			if(!success)
 				goto Backtrack;
 		}else{
+			Predicate *pred = findpredicate(currentmodule->predicates, goal);
+			if(pred == nil){
+				print("No predicate matches: %S\n", prettyprint(goal, 0, 0, 0));
+				goto Backtrack;
+			}
+
 			/* Find a clause where the head unifies with the goal */
-			clause = findclause(startclause, goal, &bindings);
-			if(clause != nil){
-				if(clause->next != nil){
-					/* Add a choicepoint. Note we create a choicepoint every time, so there is room for improvement. */
-					Choicepoint *cp = malloc(sizeof(Choicepoint));
-					cp->goalstack = copygoals(oldgoalstack);
-					cp->next = choicestack;
-					cp->retryclause = clause->next;
-					cp->id = clause->clausenr;
-					cp->currentmodule = currentmodule;
-					choicestack = cp;
-				}
-			}else{
+			clause = findclause(pred->clauses, goal, &bindings);
+			if(clause != nil)
+				addchoicepoints(clause, goal, goalstack, currentmodule);
+			else{
 Backtrack:
 				if(choicestack == nil)
 					return 0;
@@ -111,11 +99,10 @@ Backtrack:
 					print("Backtracking..\n");
 				Choicepoint *cp = choicestack;
 				choicestack = cp->next;
-				/* freegoals(goals) */
 				goalstack = cp->goalstack;
 				currentmodule = cp->currentmodule;
-				startclause = cp->retryclause;
-				goto Retry;
+				clause = cp->alternative;
+				bindings = cp->altbindings;
 			}
 		}
 
@@ -171,6 +158,26 @@ findclause(Clause *clauses, Term *goal, Binding **bindings)
 	return nil;
 }
 
+Predicate *
+findpredicate(Predicate *preds, Term *goal)
+{
+	Rune *name;
+	int arity;
+
+	name = goal->text;
+	if(goal->tag == AtomTerm)
+		arity = 0;
+	else
+		arity = goal->arity;
+
+	Predicate *p;
+	for(p = preds; p != nil; p = p->next){
+		if(runestrcmp(p->name, name) == 0 && p->arity == arity)
+			return p;
+	}
+	return nil;
+}
+
 int
 unify(Term *a, Term *b, Binding **bindings)
 {
@@ -293,3 +300,40 @@ copygoals(Goal *goals)
 	}else
 		return nil;
 }
+
+void
+addchoicepoints(Clause *clause, Term *goal, Goal *goals, Module *mod){
+	/* Find all alternative clauses that would have matched, and create a choicepoint for them */
+	Choicepoint *cps = nil;
+	Choicepoint *last = nil;
+
+	Clause *alt = clause->next;
+	while(alt != nil){
+		Binding *altbindings = nil;
+		clause = findclause(alt, goal, &altbindings);
+		if(clause){
+			/* Add choicepoint here */
+			Choicepoint *cp = malloc(sizeof(Choicepoint));
+			cp->goalstack = copygoals(goals);
+			cp->next = nil;
+			cp->alternative = clause;
+			cp->altbindings = altbindings;
+			cp->id = clause->clausenr;
+			cp->currentmodule = mod;
+			if(cps == nil){
+				cps = cp;
+				last = cp;
+			}else{
+				last->next = cp;
+				last = cp;
+			}
+			alt = clause->next;
+		}else
+			alt = nil;
+	}
+
+	if(last){
+		last->next = choicestack;
+		choicestack = cps;
+	}
+}
\ No newline at end of file