diff -r a0c469a58ed4 -r 3cd6c850c252 marking4/postfix_test9.scala
--- a/marking4/postfix_test9.scala	Wed Oct 30 12:47:10 2019 +0000
+++ b/marking4/postfix_test9.scala	Wed Oct 30 14:07:58 2019 +0000
@@ -1,3 +1,5 @@
+import CW9b._
+
 
 assert(syard(split("3 + 4 * ( 2 - 1 )")) == List("3", "4", "2", "1", "-", "*", "+"))
 assert(syard(split("( ( ( 3 ) ) + ( ( 4 + ( 5 ) ) ) )")) == List("3", "4", "5", "+", "+"))