chain.dart

class Step {
  operator - (_) => this;
  operator > (other) => new Seq(this, other);
}
 
class Atom extends Step {
  final name;
 
  Atom(this.name);
 
  toString() => "${name}";
}
 
class Seq extends Step {
  final x, y;
 
  Seq(this.x, this.y);
 
  toString() => "${x} => ${y}";
}
 
var x = new Atom("x");  // Unfortunately can't be final for we use -- on it :-/
var y = new Atom("y");
var z = new Atom("z");
 
main() {
  print (x --> y --> z); // x => y => z
}