Simplify C interface to Prolog.

1 files changed, 76 insertions, 0 deletions

diff --git a/c/pl.c b/c/pl.c
new file mode 100644
index 0000000..6f7a07d
--- /dev/null
+++ b/c/pl.c
@@ -0,0 +1,76 @@
+#include <stdarg.h>
+#include <string.h>
+#include <SWI-Prolog.h>
+
+int
+Pl(char *szMod, char *szPred, char *szFmt, ...)
+{
+	int i, iArity;
+	term_t t;
+	va_list vl;
+
+	va_start(vl, szFmt);
+	iArity = strlen(szFmt);
+	t = PL_new_term_refs(iArity);
+
+	for (i = 0; szFmt[i]; i++) {
+		switch (szFmt[i]) {
+		case 'I':
+		    {
+			int x;
+			x = va_arg(vl, int);
+			if (!PL_put_integer(t+i, x)) return 0;
+			break;
+		    }
+		case 'A':
+		    {
+			atom_t x;
+			x = va_arg(vl, atom_t);
+			if (!PL_put_atom(t+i, x)) return 0;
+			break;
+		    }
+		case 'S':
+		    {
+			atom_t a;
+			char *x;
+			x = va_arg(vl, char *);
+			a = PL_new_atom(x);
+			if (!PL_put_atom(t+i, a)) return 0;
+			break;
+		    }
+		}
+	}
+
+	if (!PL_call_predicate(NULL, PL_Q_NORMAL,
+		PL_predicate(szPred, iArity, szMod), t))
+		return 0;
+
+	for (i = 0; szFmt[i]; i++) {
+		switch (szFmt[i]) {
+		case 'i':
+		    {
+			int *lp;
+			lp = va_arg(vl, int *);
+			if (!PL_get_integer(t+i, lp)) return 0;
+			break;
+		    }
+		case 'a':
+		    {
+			atom_t *lp;
+			lp = va_arg(vl, atom_t *);
+			if (!PL_get_atom(t+i, lp)) return 0;
+			break;
+		    }
+		case 's':
+		    {
+			char **lp;
+			lp = va_arg(vl, char **);
+			if (!PL_get_atom_chars(t+i, lp)) return 0;
+			break;
+		    }
+		}
+	}
+
+	va_end(vl);
+	return 1;
+}