+
+GList* first_rule (GHashTable* first, rule_t* rule)
+{
+
+ GHashTable* terminals;
+ GList* symbols;
+ GList* l;
+
+ l = NULL;
+
+ symbols = grammar_get_rule (rule);
+
+ terminals = g_hash_table_new_full (symbol_hash, symbol_equal, g_free, NULL);
+
+ while (symbols != NULL)
+ {
+ first_set_t* first_set;
+ symbol_t* symbol;
+ symbol = (symbol_t*) symbols->data;
+ if (symbol->terminal)
+ {
+ g_hash_table_insert (terminals, symbol_copy (symbol), NULL);
+ break;
+ }
+ if (!g_hash_table_lookup_extended (first, symbol, NULL,
+ (gpointer*) &first_set))
+ {
+ g_hash_table_destroy (terminals);
+ return NULL;
+ }
+ first_set_union (terminals, first_set->terminals);
+ if (first_set->has_empty == FALSE)
+ break;
+ symbols = g_list_next (symbols);
+ }
+
+ if (symbols == NULL)
+ l = g_list_prepend (l, symbol_new (TRUE, 0));
+ g_hash_table_foreach (terminals, put_key_on_list, &l);
+
+ g_hash_table_destroy (terminals);
+
+ return l;
+
+}