All symbols created with UNDEFINED_TYPECODE by default. AST nodes with undefined typecode are evaluated by invoking the method __eval__ on the node. Typecode is looked up in the immediate delegate of a node only. Object.__eval__() is primitive and returns self.

minproto.leg

@@ -1,6 +1,6 @@
 # minproto.leg -- minimal prototype langauge for semantic experiments
 #
-# last edited: 2024-05-09 13:59:36 by piumarta on zora-1034.local
+# last edited: 2024-05-10 03:08:44 by piumarta on zora-1034.local
 
 %{
 ;
@@ -98,6 +98,7 @@ doProtos(declareProto);
 
 #define  declareTypecode(NAME)	t##NAME,
 enum typecode {
+    UNDEFINED_TYPECODE,
     doProtos(declareTypecode)
 };
 #undef   declareTypecode
@@ -396,6 +397,9 @@ oop newSymbol(char *name)
     oop obj = make(Symbol);
     _set(obj, Symbol,name,  strdup(name));
     _set(obj, Symbol,value, UNDEFINED);
+# if TYPECODES
+    _set(obj, Symbol,typecode, UNDEFINED_TYPECODE);
+# endif
     return obj;
 }
 
@@ -559,6 +563,7 @@ oop Object_get(oop obj, oop key)
 	    ssize_t ind = Object_find(obj, key);
 	    if (ind >= 0) return _get(obj, Object,properties)[ind].val;
 	    o = _getDelegate(obj);
+	    if (nil == o) o = pObject;
 	    break;
 	}
     }
@@ -580,7 +585,7 @@ oop getvar(oop obj, oop key)
 	obj = _getDelegate(obj);
     }
     oop value = _get(key, Symbol,value); // asserts is(Symbol,key)
-    if (!value) fatal("undefined variable: %s", storeString(key, 0));
+    if (UNDEFINED == value) fatal("undefined variable: %s", storeString(key, 0));
     return value;
 }
 
@@ -1859,9 +1864,11 @@ oop Literal_eval(oop exp, oop env)
     int              psize   = _get(object, Object,psize);
     for (int i = 0;  i < psize;  ++i)
 	Object_put(clone, kvs[i].key, eval(kvs[i].val, env));
+# if 0
     oop delegate = _getDelegate(object);
     if (nil != delegate)
 	Object_put(clone, prop_delegate, eval(delegate, env));
+# endif
     return clone;
 }
 
@@ -2187,9 +2194,8 @@ oop getArgType(oop args, int index, int type, char *who)
 enum typecode getTypecode(oop exp)
 {
     oop delegate       = _getDelegate(exp);
-    oop name           = Object_get(delegate, prop_name);
-    enum typecode type = _get(name, Symbol,typecode);
-    return type;
+    oop name           = Object_getLocal(delegate, prop_name);
+    return is(Symbol, name) ? _get(name, Symbol,typecode) : UNDEFINED_TYPECODE;
 }
 
 #else // !TYPECODES
@@ -2217,25 +2223,18 @@ doProtos(defineCodeOn)
 
 static inline oop evalobj(oop exp, oop env)
 {
-# if !TYPECODES
-
-    oop delegate  = _getDelegate(exp);
-    oop evaluator = Object_get(delegate, prop_eval);
-    return apply(evaluator, exp, new(pObject), env);
-
-# else // TYPECODES
-
-    enum typecode type = getTypecode(exp);
-
-#   define defineEval(NAME) case t##NAME: return NAME##_eval(exp, env);
-    switch (type) {
+# if TYPECODES
+    switch (getTypecode(exp)) {
+	case UNDEFINED_TYPECODE:
+	    break;
+#       define defineEval(NAME) case t##NAME: return NAME##_eval(exp, env);
 	doProtos(defineEval);
+#       undef defineEval
     }
-#   undef defineEval
-
-    return exp;
-
 # endif // TYPECODES
+
+    oop evaluator = Object_get(exp, prop_eval);
+    return apply(evaluator, exp, new(pObject), env);
 }
 
 long evaluations = 0;
@@ -2349,6 +2348,11 @@ oop prim_eval(oop func, oop self, oop args, oop env)
     return result;
 }
 
+oop prim___eval__(oop func, oop self, oop args, oop env)
+{
+    return self;
+}
+
 oop prim_print(oop func, oop self, oop args, oop env)
 {
     int argc     = _get(args, Object,isize);
@@ -2530,19 +2534,19 @@ int main(int argc, char **argv)
 
     pObject = nil;
 
-# define defineProto(NAME)						\
-    p##NAME = new(pObject);						\
-    Object_put(p##NAME, prop_name, intern(#NAME));			\
-    _set(intern(#NAME), Symbol,value,    p##NAME);			\
+# define defineProto(NAME)				\
+    p##NAME = new(pObject);				\
+    Object_put(p##NAME, prop_name, intern(#NAME));	\
+    _set(intern(#NAME), Symbol,value, p##NAME);
 
     doProtos(defineProto);
     doTypes(defineProto);
 
 # undef defineProto
 
-#if TYPECODES
+    Object_put(pObject, prop_eval, newPrimitive(prim___eval__));	// inherited by all objects
 
-    Object_put(pObject, prop_eval, newPrimitive(prim_env));	// inherited by all objects
+#if TYPECODES
 
 # define defineEvaluator(NAME)						\
     _set(intern(#NAME), Symbol,typecode, t##NAME);