Add support for Prolog exceptions.

1 files changed, 35 insertions, 4 deletions

diff --git a/c/pl.cpp b/c/pl.cpp
index 3172090..1fbc4e7 100644
--- a/c/pl.cpp
+++ b/c/pl.cpp
@@ -1,9 +1,40 @@
 #include <SWI-Prolog.h>
+#include "defs.h"
 
-int Pl(const char *szMod, const char *szPred)
+Query::Query(module_t ctx, predicate_t p, term_t t0)
+{
+	m_q = PL_open_query(ctx, PL_Q_CATCH_EXCEPTION, p, t0);
+}
+
+Query::~Query()
+{
+	PL_cut_query(m_q);
+}
+
+int Query::Cut()
+{
+	if (PL_cut_query(m_q)) return 1;
+	if (term_t t = PL_exception(m_q)) throw t;
+	return 0;
+}
+
+int Query::Close()
+{
+	if (PL_close_query(m_q)) return 1;
+	if (term_t t = PL_exception(m_q)) throw t;
+	return 0;
+}
+
+int Query::NextSolution()
+{
+	if (PL_next_solution(m_q)) return 1;
+	if (term_t t = PL_exception(m_q)) throw t;
+	return 0;
+}
+
+int Plx(const char *szMod, const char *szPred)
 {
 	term_t t = PL_new_term_refs(0);
-	if (!PL_call_predicate(NULL, PL_Q_CATCH_EXCEPTION, PL_predicate(szPred, 0, szMod), t))
-		return 0;
-	return 1;
+	Query q(NULL, PL_predicate(szPred, 0, szMod), t);
+	return q.NextSolution();
 }