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#!/usr/bin/env amm | |
load.ivy("org.typelevel" %% "cats" % "0.7.0") | |
@ | |
import cats.{Id, ~>} | |
import cats.data.State | |
import cats.free._ | |
import cats.free.Free._ | |
import scala.collection.mutable | |
type NoteId = Int | |
type Time = Int | |
type Pitch = Int | |
type Duration = Int | |
sealed trait Command[A] | |
case class On(pitch: Pitch) extends Command[Int] | |
case class Off(id: Int) extends Command[Unit] | |
case object Chill extends Command[Unit] | |
def on(pitch: Pitch): Free[Command, Int] = | |
Free.liftF[Command, Int](On(pitch)) | |
def off(id: Int): Free[Command, Unit] = | |
Free.liftF[Command, Unit](Off(id)) | |
def chill: Free[Command, Unit] = | |
Free.liftF[Command, Unit](Chill) | |
val program = for { | |
a <- on(10) | |
_ <- chill | |
b <- on(20) | |
_ <- chill | |
c <- on(30) | |
_ <- chill | |
_ <- off(a) | |
_ <- off(b) | |
_ <- chill | |
_ <- chill | |
_ <- off(c) | |
} yield () | |
case class PlayerState(nextId: NoteId = 0, playing: Map[NoteId, Pitch] = Map.empty, output: List[List[Pitch]] = Nil) | |
type Output[A] = State[PlayerState, A] | |
object TestInterpreter extends (Command ~> Output) { | |
def apply[A](cmd: Command[A]): Output[A] = cmd match { | |
case On(pitch) => | |
State { state => | |
val id = state.nextId | |
val newState = state.copy(state.nextId + 1, state.playing + (id -> pitch)) | |
(newState, id) | |
} | |
case Off(id) => | |
State.modify(state => state.copy(playing = state.playing - id)) | |
case Chill => | |
State.modify(state => state.copy(output = state.output :+ state.playing.values.toList.sorted)) | |
} | |
} | |
val endState = program.foldMap(TestInterpreter).runS(PlayerState()).value | |
println(endState) | |
endState.output.foreach(println) |
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