1 files changed, 53 insertions, 29 deletions

diff --git a/builtins.c b/builtins.c
index cbb01e6..f6d667b 100644
--- a/builtins.c
+++ b/builtins.c
@@ -6,6 +6,15 @@
 
 #define BuiltinProto(name) int name(Term *, Term *, Goal **, Choicepoint **, Binding **)
 #define Match(X, Y) (runestrcmp(name, X) == 0 && arity == Y)
+#define Throw(What) do{\
+	Term *t = mkcompound(L"throw", 1, What); \
+	Goal *g = malloc(sizeof(Goal)); \
+	g->goal = t; \
+	g->catcher = nil; \
+	g->next = *goals; \
+	*goals = g; \
+	return 1; \
+}while(0)
 
 BuiltinProto(builtinfail);
 BuiltinProto(builtincall);
@@ -18,7 +27,6 @@ BuiltinProto(builtinatomic);
 BuiltinProto(builtincompound);
 BuiltinProto(builtinnonvar);
 BuiltinProto(builtinnumber);
-BuiltinProto(builtinstring);
 BuiltinProto(builtincompare);
 BuiltinProto(builtinfunctor);
 BuiltinProto(builtinarg);
@@ -28,6 +36,15 @@ BuiltinProto(builtincatch);
 BuiltinProto(builtinthrow);
 
 int compareterms(Term *, Term *);
+Term *instantiationerror(void);
+Term *typeerror(Rune *, Term *);
+Term *domainerror(Rune *, Term *);
+Term *existenceerror(Rune *, Term *);
+Term *permissionerror(Rune *, Rune *, Term *);
+Term *representationerror(Rune *);
+Term *evaluationerror(Rune *);
+Term *resourceerror(Rune *);
+Term *syntaxerror(Rune *);
 
 Builtin
 findbuiltin(Term *goal)
@@ -71,8 +88,6 @@ findbuiltin(Term *goal)
 		return builtinnonvar;
 	if(Match(L"number", 1))
 		return builtinnumber;
-	if(Match(L"string", 1))
-		return builtinstring;
 	if(Match(L"compare", 3))
 		return builtincompare;
 	if(Match(L"functor", 3))
@@ -224,17 +239,6 @@ builtinnumber(Term *database, Term *goal, Goal **goals, Choicepoint **choicestac
 	return (arg->tag == NumberTerm);
 }
 
-int
-builtinstring(Term *database, Term *goal, Goal **goals, Choicepoint **choicestack, Binding **bindings)
-{
-	USED(database);
-	USED(goals);
-	USED(choicestack);
-	USED(bindings);
-	Term *arg = goal->children;
-	return (arg->tag == StringTerm);
-}
-
 #define Compare(A, B) ((A < B) ? -1 : ((A > B) ? 1 : 0))
 
 int
@@ -262,7 +266,6 @@ compareterms(Term *t1, Term *t2)
 			}else
 				result = Compare(t1->numbertype, t2->numbertype);
 			break;
-		case StringTerm:
 		case AtomTerm:
 			result = runestrcmp(t1->text, t2->text);
 			break;
@@ -364,8 +367,10 @@ builtinarg(Term *database, Term *goal, Goal **goals, Choicepoint **choicestack,
 	Term *term = n->next;
 	Term *arg = term->next;
 
-	if(n->tag != NumberTerm || n->numbertype != NumberInt || n->ival < 0)
+	if(n->tag != NumberTerm || n->numbertype != NumberInt)
 		return 0;
+	if(n->ival < 0)
+		Throw(domainerror(L"not_less_than_zero", n));
 	if(term->tag != CompoundTerm)
 		return 0;
 	if(n->ival >= term->arity)
@@ -377,18 +382,6 @@ builtinarg(Term *database, Term *goal, Goal **goals, Choicepoint **choicestack,
 	return unify(arg, t, bindings);
 }
 
-Term *
-mklist(Term *elems)
-{
-	if(elems == nil)
-		return mkatom(L"[]");
-	else{
-		Term *t = copyterm(elems, nil);
-		t->next = mklist(elems->next);
-		return mkcompound(L".", 2, t);
-	}
-}
-
 int
 listlength(Term *term)
 {
@@ -559,4 +552,35 @@ builtinthrow(Term *database, Term *goal, Goal **goals, Choicepoint **choicestack
 		}
 	}
 	return 0;
-}
\ No newline at end of file
+}
+
+/* Helpers to create error terms */
+
+Term *
+instantiationerror(void)
+{
+	return mkatom(L"instantiation_error");
+}
+
+Term *
+typeerror(Rune *validtype, Term *culprit)
+{
+	Term *valid = mkatom(validtype);
+	valid->next = copyterm(culprit, nil);
+	return mkcompound(L"type_error", 2, valid);
+}
+
+Term *
+domainerror(Rune *validdomain, Term *culprit)
+{
+	Term *valid = mkatom(validdomain);
+	valid->next = copyterm(culprit, nil);
+	return mkcompound(L"domain_error", 2, valid);
+}
+
+Term *existenceerror(Rune *, Term *);
+Term *permissionerror(Rune *, Rune *, Term *);
+Term *representationerror(Rune *);
+Term *evaluationerror(Rune *);
+Term *resourceerror(Rune *);
+Term *syntaxerror(Rune *);
\ No newline at end of file