Keep token positions when lexing

This will allow us to match line edits to original source locations.

1 files changed, 1 insertions, 1 deletions

diff --git a/prolog/engine.py b/prolog/engine.py
index 6087bbc..299d2eb 100755
--- a/prolog/engine.py
+++ b/prolog/engine.py
@@ -139,7 +139,7 @@ class PrologEngine(object):
         try:
             start = 0
             for idx in range(len(tokens)):
-                if tokens[idx] != ('PERIOD', '.') or idx - start <= 1:
+                if tokens[idx].type != 'PERIOD' or idx - start <= 1:
                     continue
                 rule = stringify(tokens[start:idx])
                 orig_rule = rule