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class Dfa {
var states = Seq.empty[State]
var finalStates = Seq.empty[State]
var currentState : State = null
var input:String=""
val transition = new Transition
val transitionMap = transition.transitionMap
def states( block: => Seq[State] ): Dfa = {
states = block
this
}
def finalStates( block: => Seq[State] ): Dfa = {
finalStates = block
this
}
def transitions( f: Transition => Unit ): Dfa = {
f(transition)
this
}
def startFrom(start: State):Dfa = {
currentState=start
this
}
def withInput(input:String):Dfa = {
this.input=input
this
}
def run : Boolean = {
input.foreach { ch =>
transitionMap.get( (currentState,ch) ) match {
case Some(state) => currentState=state
case None => throw new Exception(s"You must provide transition function for input '$ch' when state is ${currentState.toString}")
}
}
finalStates contains currentState
}
}
class Transition {
val transitionMap : scala.collection.mutable.HashMap[(State,Char),State] =
new scala.collection.mutable.HashMap()
def on(ch : Char) : TransitionFrom = new TransitionFrom(this,ch)
}
class TransitionFrom(val tr: Transition , val ch : Char) {
def from(s: State) : TransitionTo = new TransitionTo(tr,ch,s)
}
class TransitionTo(val tr:Transition , val ch : Char,val from:State) {
def to(s : State) : Unit = {
tr.transitionMap += (from,ch)->s
}
}
object Dfa {
def newDfa( f: Dfa => Unit ) : Dfa = {
val dfa = new Dfa
f(dfa)
dfa
}
}
object Main {
def main(args: Array[String]): Unit = {
import Dfa._
val dfa = newDfa { dfa =>
dfa states {
Seq(S0, S1, S2, S3)
}
dfa finalStates {
Seq(S2)
}
dfa transitions { transition =>
transition on '0' from S0 to S1
transition on '1' from S0 to S3
transition on '0' from S1 to S2
transition on '1' from S1 to S1
transition on '0' from S2 to S2
transition on '1' from S2 to S1
transition on '0' from S3 to S3
transition on '1' from S3 to S3
}
} startFrom S0 withInput "010101011110110110000"
val hasInputAccepted = dfa.run
}
}
sealed trait State
final case object S0 extends State
final case object S1 extends State
final case object S2 extends State
final case object S3 extends State
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