C-interface

packages/python/pl2py.c

@@ -387,7 +387,7 @@ PyObject *term_to_python(term_t t, bool eval, PyObject *o, bool cvt) {
 	  if (entry_to_dictionary(dict, yt, eval, cvt))
 	    return dict;
 	  else
-	    return NULL;         
+	    return Py_None;         
         }
        atom_t name;
         int arity;
@@ -424,8 +424,8 @@ PyObject *term_to_python(term_t t, bool eval, PyObject *o, bool cvt) {
 }
 
 PyObject *yap_to_python(YAP_Term t, bool eval, PyObject *o, bool cvt) {
-  if (t == 0)
-    return NULL;
+  if (t == 0 || t == TermNone)
+    return Py_None;
   term_t yt = YAP_InitSlot(t);
   o = term_to_python(yt, eval, o, cvt);
   PL_reset_term_refs(yt);

packages/python/py2pl.c

@@ -55,8 +55,9 @@ static Term python_to_term__(PyObject *pVal) {
   if (pVal == Py_None) {
     // fputs("<<*** ",stderr);Yap_DebugPlWrite(YAP_GetFromSlot(t));   fputs("
     // >>***\n",stderr);
-    return YAP_MkVarTerm();
+    //return YAP_MkVarTerm();
     // fputs("<<*** ",stderr);Yap_DebugPlWrite(YAP_GetFromSlot(t));   fputs("
+    return MkAtomTerm(Yap_LookupAtom("none"));
     // >>***\n",stderr);
   } else if (PyBool_Check(pVal)) {
     if(PyObject_IsTrue(pVal)) return TermTrue;

packages/python/pypreds.c

@@ -238,15 +238,16 @@ static foreign_t python_string_to(term_t f) {
     if (!PL_get_chars(f, &s, CVT_ALL | CVT_EXCEPTION | REP_UTF8)) {
       pyErrorAndReturn(false);
     }
-    if (!strcmp(s,"atom"))
+    if (!strcmp(s,"atom")) {
       pyStringToString = false;
-    if (!strcmp(s,"string"))
+      return true;
+    }
+    if (!strcmp(s,"string")) {
       pyStringToString = true;
-    else
-      return false;
-    return true;
+      return true;
+    }
   }
-  return true;
+  return false;
 }
 
 static foreign_t python_builtin_eval(term_t caller, term_t dict, term_t out) {