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Diffstat (limited to 'docs/examples/monads/directInterpreter.scala')
-rw-r--r-- | docs/examples/monads/directInterpreter.scala | 55 |
1 files changed, 0 insertions, 55 deletions
diff --git a/docs/examples/monads/directInterpreter.scala b/docs/examples/monads/directInterpreter.scala deleted file mode 100644 index 06fffba8e2..0000000000 --- a/docs/examples/monads/directInterpreter.scala +++ /dev/null @@ -1,55 +0,0 @@ -object directInterpreter { - - 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; - case class Num(n: Int) extends Value; - case class Fun(f: Value => Value)extends Value; - - def showval(v: Value): String = v match { - case Wrong => "<wrong>" - case Num(n) => n.toString() - case Fun(f) => "<function>" - } - - type Environment = List[Pair[Name, Value]]; - - def lookup(x: Name, e: Environment): Value = e match { - case List() => Wrong - case Pair(y, b) :: e1 => if (x == y) b else lookup(x, e1) - } - - def add(a: Value, b: Value): Value = Pair(a, b) match { - case Pair(Num(m), Num(n)) => Num(m + n) - case _ => Wrong - } - - def apply(a: Value, b: Value) = a match { - case Fun(k) => k(b) - case _ => Wrong - } - - def interp(t: Term, e: Environment): Value = t match { - case Var(x) => lookup(x, e) - case Con(n) => Num(n) - case Add(l, r) => add(interp(l, e), interp(r, e)) - case Lam(x, t) => Fun(a => interp(t, Pair(x, a) :: e)) - case App(f, t) => apply(interp(f, e), interp(t, e)) - } - - def test(t: Term): String = - showval(interp(t, List())); - - val term0 = App(Lam("x", Add(Var("x"), Var("x"))), Add(Con(10), Con(11))); - - def main(args: Array[String]) = - System.out.println(test(term0)); -} |