Use immutable values in queue

1 files changed, 4 insertions, 4 deletions

diff --git a/prolog/util.py b/prolog/util.py
index f5d1865..4826f86 100644
--- a/prolog/util.py
+++ b/prolog/util.py
@@ -41,14 +41,14 @@ def decompose(code):
     for t in tokens:
         if t[0] == 'SEMI':
             if line != []:
-                lines.append(line[:])
+                lines.append(tuple(line))
                 line = []
-            lines.append([t])
+            lines.append((t,))
             continue
         if not parens:
             if t[0] in ('PERIOD', 'FROM', 'COMMA', 'EOF'):
                 if line != []:
-                    lines.append(line[:])
+                    lines.append(tuple(line))
                     line = []
                 if t[0] in ('PERIOD', 'EOF') and rule_start < len(lines):
                     rules.append((rule_start, len(lines)))
@@ -64,7 +64,7 @@ def decompose(code):
             elif t[0] == 'RBRACE' and parens[-1] == 'LBRACE':
                 parens.pop()
         line.append(t)
-    return lines, rules
+    return tuple(lines), tuple(rules)
 
 # pretty-print a list of rules
 def compose(lines, rules):