pipeline.dart

class Nothing { const Nothing(); }
class Pipeable {
  var value = const Nothing();
  operator |(f) {
    if (f == const Nothing()) {
      return value;
    } else if (value == const Nothing()) {
      value = f();
    } else {
      value = f(value);
    }
    return this;
  }
}

pipeline() => new Pipeable();
const done = const Nothing();

final response = pipeline() 
  | loadConfig
  | buildDic
  | getApp
  | getRouter
  | (_) => getDispatcher(_, request)
  | (_) => dispatchBusinessLogic(_, request, new Response())
  | renderResponse
  | buildResponse
  | emit
  | done;