ReScala basiscs

gistfile1.scala

import rescala._
import rescala.events.{ Event, ImperativeEvent }
import makro.SignalMacro.{SignalM => Signal}

object ReScalaDemo extends App {
	
	/* 
	Observer criticism 

	- inverts natural dependency order (listeners call soure to register)
	- lots of boilerplate code
	- no composition of events and handlers
	- scattering and tangling of trigger code, inconsistent firing
	*/

	/*** Events ***/
	val e1 : ImperativeEvent[Int] = new ImperativeEvent[Int]()
	e1 += (x => println("x:" + x)) // register handler
	e1(1) // firing the event, passing 1 as value
	
	// handler execution order is not guaranteed deterministic
	val e2 : Event[Int] = new ImperativeEvent[Int]()
	val e3 : Event[Int] = e1 || e2 // declarative event, fired when e1 or e2 fire
	// create new event with evt. parameter mapping
	val e4 : Event[String] = e1 map ( (x:Int) => x.toString) 

	/*** Vars ***/
	// vars: primitive reactive values, manual update
	val v1 : Var[Int] = Var(1)
	val v2 : Var[Int] = Var(2)
	v2()= 3// assign 3 to v2 
	
	/*** Signals ***/
	// Signals: reactive expressions, updated automatically
	val s1 = Signal {
		// signals can depend on vars
		v1() + v2() 
		// should be side-effect free!!!
	}
	val s2 = Signal {
		// signals can depend on other signals
		s1() * s1() 
	}

	s1.get // retrieve current value of signal
	val s1e : Event[Int] = s1.changed // signal -> event
	val e1s : Signal[Int] = e1.latest(0) // event -> default value -> signal
}