Optimize prolog.util.stringify (~15% faster)

1 files changed, 7 insertions, 17 deletions

diff --git a/prolog/util.py b/prolog/util.py
index fc243f2..eb026fe 100644
--- a/prolog/util.py
+++ b/prolog/util.py
@@ -19,24 +19,14 @@ operators = set([
     'PLUS', 'MINUS', 'STAR', 'DIV', 'IDIV', 'MOD',
     'POW', 'SEMI'
 ])
-def stringify(tokens, indent=''):
-    s = indent
-    for t in tokens:
-        if t[0] in operators:
-            s += ' '
-
-        if t[0] == 'FROM':
-            s += ':-\n  ' + indent
-        elif t[0] == 'PERIOD':
-            s += '.\n' + indent
-        elif t[0] == 'COMMA':
-            s += ', '
+def stringify(tokens):
+    def token_str(t):
+        if t[0] in ('PERIOD', 'COMMA'):
+            return t[1] + ' '
         elif t[0] in operators:
-            s += t[1] + ' '
-        else:
-            s += t[1]
-
-    return s.strip().replace('\n', ' ').replace('\t', ' ')
+            return ' ' + t[1] + ' '
+        return t[1]
+    return ''.join(map(token_str, tokens))
 
 # return a list of lines in 'code', and a list of rule indexes
 def decompose(code):