115 // size of a regular expressions - for testing purposes 

   116 def size(r: Rexp) : Int = r match {

   117   case ZERO => 1

   118   case ONE => 1

   119   case CHAR(_) => 1

   120   case ALT(r1, r2) => 1 + size(r1) + size(r2)

   121   case SEQ(r1, r2) => 1 + size(r1) + size(r2)

   122   case STAR(r) => 1 + size(r)

   123   case NTIMES(r, _) => 1 + size(r)

   124 }

   125 

   126 

   127 // string of a regular expressions - for testing purposes 

   128 def string(r: Rexp) : String = r match {

   129   case ZERO => "0"

   130   case ONE => "1"

   131   case CHAR(c) => c.toString 

   132   case ALT(r1, r2) => s"(${string(r1)} + ${string(r2)})"

   133   case SEQ(CHAR(c), CHAR(d)) => s"${c}${d}"

   134   case SEQ(r1, r2) => s"(${string(r1)} ~ ${string(r2)})"

   135   case STAR(r) => s"(${string(r)})*"

   136   case NTIMES(r, n) =>  s"(${string(r)}){${n}}"

   137 }

   138 

   139 

   140 // test: ("a" | "aa")*

   141 val EVIL3 = STAR(ALT(CHAR('a'), SEQ(CHAR('a'), CHAR('a'))))

   142 

   143 //test: ("" | "a" | "aa")*

   144 val EVIL3 = STAR(ALT(ONE, ALT(CHAR('a'), SEQ(CHAR('a'), CHAR('a')))))

   145 

   146 val t1  = ders2("a".toList, EVIL3)

   147 val t1s = simp(t1) 

   148 val t2  = ders2("aa".toList, t1s)

   149 val t2s = simp(t2)

   150 val t3  = ders2("aaa".toList, t2s)

   151 val t3s = simp(t3)

   152 val t4  = ders2("aaaa".toList, t3s)

   153 val t4s = simp(t4)

   154 println(string(t1) + "    " + size(t1))

   155 println("s " + string(t1s) + "    " + size(t1s))

   156 println(string(t2) + "    " + size(t2))

   157 println("s " + string(t2s) + "    " + size(t2s))

   158 println(string(t3) + "    " + size(t3))

   159 println("s " + string(t3s) + "    " + size(t3s))

   160 println(string(t4) + "    " + size(t4))

   161 println("s " + string(t4s) + "    " + size(t4s))