Add support for builtins, and implement true/0, fail/0, call/1, and !/0 builtins

1 files changed, 17 insertions, 0 deletions

diff --git a/dat.h b/dat.h
index d5dbfef..a090afb 100644
--- a/dat.h
+++ b/dat.h
@@ -1,5 +1,8 @@
 typedef struct Term Term;
 typedef struct Binding Binding;
+typedef struct Goal Goal;
+typedef struct Choicepoint Choicepoint;
+typedef int (*Builtin)(Term *, Term *, Goal **, Choicepoint **, Binding **);
 
 struct Term
 {
@@ -23,6 +26,20 @@ struct Binding
 	Binding *next;
 };
 
+struct Goal
+{
+	Term *goal;
+	Goal *next;
+};
+
+struct Choicepoint
+{
+	Goal *goalstack;
+	Term *retryclause;
+	uvlong id; /* Unique number for each clause. Used to know where to cut to. */
+	Choicepoint *next;
+};
+
 enum {
 	CompoundTerm,
 	AtomTerm,