diff -r 940b6c68102a -r 72688efdf17c testing4/re_test3.scala
--- a/testing4/re_test3.scala	Thu Oct 31 11:33:02 2019 +0000
+++ b/testing4/re_test3.scala	Thu Oct 31 12:01:56 2019 +0000
@@ -1,13 +1,21 @@
-
+import CW9c._
 
 
 assert(simp(ZERO | ONE) == ONE)
 assert(simp(STAR(ZERO | ONE)) == STAR(ZERO | ONE))
 assert(simp(ONE ~ (ONE ~ (ONE ~ CHAR('a')))) == CHAR('a'))
+assert(simp(((ONE ~ ONE) ~ ONE) ~ CHAR('a')) == CHAR('a'))
+assert(simp(((ONE | ONE) ~ ONE) ~ CHAR('a')) == CHAR('a'))
 assert(simp(ONE ~ (ONE ~ (ONE ~ ZERO))) == ZERO)
 assert(simp(ALT(ONE ~ (ONE ~ (ONE ~ ZERO)), CHAR('a'))) == CHAR('a'))
 assert(simp(CHAR('a') | CHAR('a')) == CHAR('a'))
+assert(simp(CHAR('a') ~ CHAR('a')) == CHAR('a') ~ CHAR('a'))
 assert(simp(ONE | CHAR('a')) == (ONE | CHAR('a')))
 assert(simp(ALT((CHAR('a') | ZERO) ~ ONE,
-               ((ONE | CHAR('b')) | CHAR('c')) ~ (CHAR('d') ~ ZERO))) == CHAR('a'))
+                  ((ONE | CHAR('b')) | CHAR('c')) ~ (CHAR('d') ~ ZERO))) == CHAR('a'))
+assert(simp((ZERO | ((ZERO | ZERO) | (ZERO | ZERO))) ~ ((ONE | ZERO) | ONE ) ~ (CHAR('a'))) == ZERO)
+assert(simp(ALT(ONE | ONE, ONE | ONE)) == ONE)
+assert(simp(ALT(ZERO | CHAR('a'), CHAR('a') | ZERO)) == CHAR('a'))
+assert(simp(ALT(ONE | CHAR('a'), CHAR('a') | ONE)) == ALT(ONE | CHAR('a'), CHAR('a') | ONE))
 
+