1 files changed, 75 insertions, 0 deletions

diff --git a/builtins.c b/builtins.c
index 4a2161f..cbb01e6 100644
--- a/builtins.c
+++ b/builtins.c
@@ -24,6 +24,8 @@ BuiltinProto(builtinfunctor);
 BuiltinProto(builtinarg);
 BuiltinProto(builtinuniv);
 BuiltinProto(builtinis);
+BuiltinProto(builtincatch);
+BuiltinProto(builtinthrow);
 
 int compareterms(Term *, Term *);
 
@@ -81,6 +83,10 @@ findbuiltin(Term *goal)
 		return builtinuniv;
 	if(Match(L"is", 2))
 		return builtinis;
+	if(Match(L"catch", 3))
+		return builtincatch;
+	if(Match(L"throw", 1))
+		return builtinthrow;
 
 	return nil;
 }
@@ -105,6 +111,7 @@ builtincall(Term *database, Term *goal, Goal **goals, Choicepoint **choicestack,
 
 	Goal *g = malloc(sizeof(Goal));
 	g->goal = goal->children;
+	g->catcher = nil;
 	g->next = *goals;
 	*goals = g;
 
@@ -484,4 +491,72 @@ builtinis(Term *database, Term *goal, Goal **goals, Choicepoint **choicestack, B
 		return unify(result, realresult, bindings);
 	else
 		return 0;
+}
+
+int
+builtincatch(Term *database, Term *goal, Goal **goals, Choicepoint **choicestack, Binding **bindings)
+{
+	USED(database);
+	USED(choicestack);
+	USED(bindings);
+
+	Term *catchgoal = goal->children;
+	Term *catcher = catchgoal->next;
+	Term *recover = catcher->next;
+
+	Goal *catchframe = malloc(sizeof(Goal));
+	catchframe->goal = recover;
+	catchframe->catcher = catcher;
+	catchframe->next = *goals;
+	*goals = catchframe;
+
+	Goal *g = malloc(sizeof(Goal));
+	g->goal = catchgoal;
+	g->catcher = nil;
+	g->next = *goals;
+	*goals = g;
+
+	return 1;
+}
+
+int
+builtinthrow(Term *database, Term *goal, Goal **goals, Choicepoint **choicestack, Binding **bindings)
+{
+	USED(database);
+	USED(choicestack);
+	USED(bindings);
+	USED(goals);
+
+	Term *ball = goal->children;
+
+	print("Throwing: %S\n", prettyprint(ball));
+	Goal *g;
+	for(g = *goals; g != nil; g = g->next){
+		if(g->catcher == nil)
+			continue;
+
+		if(unify(g->catcher, ball, bindings)){
+			if(g->goal == nil){
+				/* As soon as we have print facilities as builtins, we can avoid this by having the protector frame have a unhandled exception handler*/
+				print("Unhandled exception: %S\n", prettyprint(ball));
+				exits("exception");
+				return 0;
+			}else{
+				*goals = g->next;
+				Goal *newgoal = malloc(sizeof(Goal));
+				newgoal->goal = copyterm(g->goal, nil);
+				newgoal->catcher = nil;
+				newgoal->next = *goals;
+				*goals = newgoal;
+				applybinding(newgoal->goal, *bindings);
+
+				Choicepoint *cp = *choicestack;
+				while(cp != nil && cp->id >= goal->clausenr)
+					cp = cp->next;
+				*choicestack = cp;
+				return 1;
+			}
+		}
+	}
+	return 0;
 }
\ No newline at end of file