diff -r 6f508bcdaa30 -r e61ffb28994d progs/nfa2.scala
--- a/progs/nfa2.scala	Tue Apr 11 06:22:46 2017 +0800
+++ b/progs/nfa2.scala	Sat Apr 15 22:03:59 2017 +0800
@@ -173,26 +173,26 @@
 // some examples for Thompson's
 val A = thompson(CHAR('a'))
 
-println(A.accepts("a"))
-println(A.accepts("c"))
-println(A.accepts("aa"))
+println(A.accepts("a"))   // true 
+println(A.accepts("c"))   // false 
+println(A.accepts("aa"))  // false
 
 val B = thompson(ALT("ab","ac"))
-
-println(B.accepts("ab"))
-println(B.accepts("ac"))
-println(B.accepts("bb"))
-println(B.accepts("aa"))
+ 
+println(B.accepts("ab"))   // true 
+println(B.accepts("ac"))   // true 
+println(B.accepts("bb"))   // false 
+println(B.accepts("aa"))   // false 
 
 val C = thompson(STAR("ab"))
 
-println(C.accepts(""))
-println(C.accepts("a"))
-println(C.accepts("ababab"))
-println(C.accepts("ab"))
-println(C.accepts("ac"))
-println(C.accepts("bb"))
-println(C.accepts("aa"))
+println(C.accepts(""))       // true
+println(C.accepts("a"))      // false 
+println(C.accepts("ababab")) // true
+println(C.accepts("ab"))     // true
+println(C.accepts("ac"))     // false 
+println(C.accepts("bb"))     // false 
+println(C.accepts("aa"))     // false 
 
 // regular expression matcher using Thompson's
 def matcher(r: Rexp, s: String) : Boolean = thompson(r).accepts(s)