--- a/progs/display/nfa.scala	Tue Jul 21 00:12:34 2020 +0100
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,38 +0,0 @@
-// NFAs in Scala using partial functions (returning
-// sets of states)
-//
-// needs :load dfa.scala   for states
-
-
-// type abbreviation for partial functions
-type :=>[A, B] = PartialFunction[A, B]
-
-// return an empty set when not defined
-def applyOrElse[A, B](f: A :=> Set[B], x: A) : Set[B] =
-  Try(f(x)) getOrElse Set[B]()
-
-
-// NFAs
-case class NFA[A, C](starts: Set[A],           // starting states
-                     delta: (A, C) :=> Set[A], // transition function
-                     fins:  A => Boolean) {    // final states 
-
-  // given a state and a character, what is the set of 
-  // next states? if there is none => empty set
-  def next(q: A, c: C) : Set[A] = 
-    applyOrElse(delta, (q, c))
-
-  def nexts(qs: Set[A], c: C) : Set[A] =
-    qs.flatMap(next(_, c))
-
-  // given some states and a string, what is the set 
-  // of next states?
-  def deltas(qs: Set[A], s: List[C]) : Set[A] = s match {
-    case Nil => qs
-    case c::cs => deltas(nexts(qs, c), cs)
-  }
-
-  // is a string accepted by an NFA?
-  def accepts(s: List[C]) : Boolean = 
-    deltas(starts, s).exists(fins)
-}