Fixed BNF concept evaluations

core/utils.py

@@ -220,6 +220,15 @@ def strip_tokens(tokens, strip_eof=False):
     return tokens[start: end + 1]
 
 
+def escape_char(text, to_escape):
+    res = ""
+
+    for c in text:
+        res += ("\\" + c) if c in to_escape else c
+
+    return res
+
+
 def pp(items):
     if not hasattr(items, "__iter__"):
         return str(items)