Created proper 'docs' folder for new layout.

5 files changed, 386 insertions, 0 deletions

diff --git a/docs/examples/monads/callccInterpreter.scala b/docs/examples/monads/callccInterpreter.scala
new file mode 100644
index 0000000000..934fce1a9e
--- /dev/null
+++ b/docs/examples/monads/callccInterpreter.scala
@@ -0,0 +1,84 @@
+object callccInterpreter {
+
+  type Answer = Value;
+
+  case class M[A](in: (A => Answer) => Answer) {
+    def bind[B](k: A => M[B])          = M[B](c => in (a => k(a) in c));
+    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](c => c(a));
+
+  def showM(m: M[Value]): String = (m in id).toString();
+
+  def callCC[A](h: (A => M[A]) => M[A]) =
+    M[A](c => h(a => M[A](d => c(a))) in c);
+
+  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;
+  case class Ccc(x: Name, t: 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() = "<function>"
+  }
+
+  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)) => unitM(Num(m + n))
+    case _ => unitM(Wrong)
+  }
+
+  def apply(a: Value, b: Value): M[Value] = a match {
+    case Fun(k) => k(b)
+    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 (val a <- interp(l, e);
+			   val b <- interp(r, e);
+			   val c <- add(a, b))
+                      yield c
+    case Lam(x, t) => unitM(Fun(a => interp(t, Pair(x, a) :: e)))
+    case App(f, t) => for (val a <- interp(f, e);
+			   val b <- interp(t, e);
+			   val c <- apply(a, b))
+		      yield c
+    case Ccc(x, t) => callCC(k => interp(t, Pair(x, Fun(k)) :: e))
+  }
+
+  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));
+  val term2 = Add(Con(1), Ccc("k", Add(Con(2), App(Var("k"), Con(4)))));
+
+  def main(args: Array[String]) = {
+    System.out.println(test(term0));
+    System.out.println(test(term1));
+    System.out.println(test(term2));
+  }
+}
+
diff --git a/docs/examples/monads/directInterpreter.scala b/docs/examples/monads/directInterpreter.scala
new file mode 100644
index 0000000000..0e2aae4a7b
--- /dev/null
+++ b/docs/examples/monads/directInterpreter.scala
@@ -0,0 +1,55 @@
+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));
+}
diff --git a/docs/examples/monads/errorInterpreter.scala b/docs/examples/monads/errorInterpreter.scala
new file mode 100644
index 0000000000..05dc979621
--- /dev/null
+++ b/docs/examples/monads/errorInterpreter.scala
@@ -0,0 +1,86 @@
+object errorInterpreter {
+
+  trait M[A] {
+    def show: String;
+    def bind[B](k: A => M[B]);
+    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]          =  new Suc(a);
+  def errorM[A](msg: String): M[A]  =  new Err(msg);
+
+  def showM(m: M[Value]): String = m.show;
+
+  class Suc[A](x: T) extends M[A] {
+    def bind[A](k: A => M[B]): M[B] = k(x);
+    def show: String = "Success: " + x;
+  }
+  class Err[T](msg: String) extends M[T] {
+    def bind[A](k: A => M[B]): M[B] = new Err(msg);
+    def show: String = "Error: " + msg;
+  }
+
+  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() = "<function>"
+  }
+
+  type Environment = List[Pair[Name, Value]];
+
+  def lookup(x: Name, e: Environment): M[Value] = e match {
+    case List() => errorM("unbound variable: " + x);
+    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)) => unitM(Num(m + n))
+    case _ => errorM("should be numbers: " + a + "," + b)
+  }
+
+  def apply(a: Value, b: Value): M[Value] = a match {
+    case Fun(k) => k(b)
+    case _ => errorM("should be function: " + a);
+  }
+
+  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 (val a <- interp(l, e);
+			   val b <- interp(r, e);
+			   val c <- add(a, b))
+                      yield c
+    case Lam(x, t) => unitM(Fun(a => interp(t, Pair(x, a) :: e)))
+    case App(f, t) => for (val a <- interp(f, e);
+			   val b <- interp(t, e);
+			   val 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));
+  }
+}
+
diff --git a/docs/examples/monads/simpleInterpreter.scala b/docs/examples/monads/simpleInterpreter.scala
new file mode 100644
index 0000000000..d728c620cf
--- /dev/null
+++ b/docs/examples/monads/simpleInterpreter.scala
@@ -0,0 +1,75 @@
+object simpleInterpreter {
+
+  case class M[A](value: A) {
+    def bind[B](k: A => M[B]): M[B]     =  k(value);
+    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]          =  M(a);
+
+  def showM(m: M[Value]): String = m.value.toString();
+
+  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() = "<function>"
+  }
+
+  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)) => unitM(Num(m + n))
+    case _ => unitM(Wrong)
+  }
+
+  def apply(a: Value, b: Value): M[Value] = a match {
+    case Fun(k) => k(b)
+    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 (val a <- interp(l, e);
+			   val b <- interp(r, e);
+			   val c <- add(a, b))
+                      yield c
+    case Lam(x, t) => unitM(Fun(a => interp(t, Pair(x, a) :: e)))
+    case App(f, t) => for (val a <- interp(f, e);
+			   val b <- interp(t, e);
+			   val 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));
+  }
+}
+
diff --git a/docs/examples/monads/stateInterpreter.scala b/docs/examples/monads/stateInterpreter.scala
new file mode 100644
index 0000000000..593f2d9e3e
--- /dev/null
+++ b/docs/examples/monads/stateInterpreter.scala
@@ -0,0 +1,86 @@
+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() = "<function>"
+  }
+
+  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 (val _ <- tickS) yield Num(m + n)
+    case _ => unitM(Wrong)
+  }
+
+  def apply(a: Value, b: Value): M[Value] = a match {
+    case Fun(k) => for (val _ <- tickS; val 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 (val a <- interp(l, e);
+			   val b <- interp(r, e);
+			   val c <- add(a, b))
+                      yield c
+    case Lam(x, t) => unitM(Fun(a => interp(t, Pair(x, a) :: e)))
+    case App(f, t) => for (val a <- interp(f, e);
+			   val b <- interp(t, e);
+			   val 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));
+  }
+}
+