From e55510607031aaf7b8473453f83c44a26c9b97e0 Mon Sep 17 00:00:00 2001 From: Adriaan Moors Date: Mon, 9 Dec 2013 11:06:22 -0800 Subject: Remove docs/examples; they reside at scala/scala-dist --- docs/examples/monads/stateInterpreter.scala | 86 ----------------------------- 1 file changed, 86 deletions(-) delete mode 100644 docs/examples/monads/stateInterpreter.scala (limited to 'docs/examples/monads/stateInterpreter.scala') diff --git a/docs/examples/monads/stateInterpreter.scala b/docs/examples/monads/stateInterpreter.scala deleted file mode 100644 index 97f3335dab..0000000000 --- a/docs/examples/monads/stateInterpreter.scala +++ /dev/null @@ -1,86 +0,0 @@ -package examples.monads; - -object stateInterpreter { - - type State = Int; - - val tickS = new M(s => Pair((), s + 1)); - - case class M[A](in: State => Pair[A, State]) { - def bind[B](k: A => M[B]) = M[B]{ s0 => - val Pair(a, s1) = this in s0; k(a) in s1 - } - def map[B](f: A => B): M[B] = bind(x => unitM(f(x))); - def flatMap[B](f: A => M[B]): M[B] = bind(f); - } - - def unitM[A](a: A) = M[A](s => Pair(a, s)); - - def showM(m: M[Value]): String = { - val Pair(a, s1) = m in 0; - "Value: " + a + "; Count: " + s1 - } - - type Name = String; - - trait Term; - case class Var(x: Name) extends Term; - case class Con(n: Int) extends Term; - case class Add(l: Term, r: Term) extends Term; - case class Lam(x: Name, body: Term) extends Term; - case class App(fun: Term, arg: Term) extends Term; - - trait Value; - case object Wrong extends Value { - override def toString() = "wrong" - } - case class Num(n: Int) extends Value { - override def toString() = n.toString(); - } - case class Fun(f: Value => M[Value]) extends Value { - override def toString() = "" - } - - type Environment = List[Pair[Name, Value]]; - - def lookup(x: Name, e: Environment): M[Value] = e match { - case List() => unitM(Wrong) - case Pair(y, b) :: e1 => if (x == y) unitM(b) else lookup(x, e1) - } - - def add(a: Value, b: Value): M[Value] = Pair(a, b) match { - case Pair(Num(m), Num(n)) => for (_ <- tickS) yield Num(m + n) - case _ => unitM(Wrong) - } - - def apply(a: Value, b: Value): M[Value] = a match { - case Fun(k) => for (_ <- tickS; c <- k(b)) yield c - case _ => unitM(Wrong) - } - - def interp(t: Term, e: Environment): M[Value] = t match { - case Var(x) => lookup(x, e) - case Con(n) => unitM(Num(n)) - case Add(l, r) => for (a <- interp(l, e); - b <- interp(r, e); - c <- add(a, b)) - yield c - case Lam(x, t) => unitM(Fun(a => interp(t, Pair(x, a) :: e))) - case App(f, t) => for (a <- interp(f, e); - b <- interp(t, e); - c <- apply(a, b)) - yield c - } - - def test(t: Term): String = - showM(interp(t, List())); - - val term0 = App(Lam("x", Add(Var("x"), Var("x"))), Add(Con(10), Con(11))); - val term1 = App(Con(1), Con(2)); - - def main(args: Array[String]) = { - System.out.println(test(term0)); - System.out.println(test(term1)); - } -} - -- cgit v1.2.3