diff --git a/src/arithmetic.py b/src/arithmetic.py
index 037d67a..389524b 100644
--- a/src/arithmetic.py
+++ b/src/arithmetic.py
@@ -21,7 +21,7 @@ def t_NUMBER(t):
 
 def t_EXP(t):
     r'\*\*'
-    pass
+    return t
 
 lexer = ply.lex.lex()
 
@@ -76,5 +76,3 @@ parser = ply.yacc.yacc()
 while True:
     s = input('calc> ')
     ply.yacc.parse(s)
-    if s == '':
-        break