Conceptos básicos de simultaneidad de Cat con Ref y Diferido

Acceso concurrente y transparencia referencial

Para los futuros alumnos del curso "Scala-developer "



, se preparó una traducción del material. También lo invitamos a un seminario web sobre efectos en Scala . En la lección, consideraremos el concepto de efecto y la complejidad que puede surgir si están presentes. También presentaremos el concepto de efecto funcional, consideraremos sus propiedades e implementaremos nuestro propio pequeño efecto funcional. Únete a nosotros.

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* Concurrencia - concurrencia, que permite la ejecución simultánea de varios procesos computacionales.

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/**
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     *
     * @return the updated value
     */
    public final int incrementAndGet() {
        for (;;) {
            int current = get();
            int next = current + 1;
            if (compareAndSet(current, next))
                return next;
        }
    }
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

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abstract class Ref[F[_], A] {
  def get: F[A]
  def set(a: A): F[Unit]
  def modify[B](f: A => (A, B)): F[B]
  // ... and more
}
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

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def of[F[_], A](a: A)(implicit F: Sync[F]): F[Ref[F, A]] = F.delay(unsafe(a))
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

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def modifyShared(trace: Ref[IO, Shared], msg: String): IO[Unit] = {
	for {
		sh <- trace.get()
		_ <- trace.set(Shared(sh, msg))
	} yield ()
}
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

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for {
		_ <- someRef.update(_ + 1)
		curr <- someRef.get
		_ <- IO { println(s"current value is $curr")}
	} yield ()
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

modify



 

, modify



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.

def modify[B](f: A => (A, B)): F[B] = {
      @tailrec
      def spin: B = {
        val c = ar.get
        val (u, b) = f(c)
        if (!ar.compareAndSet(c, u)) spin
        else b
      }
      F.delay(spin)
    }
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

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abstract class Deferred[F[_], A] {
  def get: F[A]
  def complete(a: A): F[Unit]
}
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

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Scala Italy 2019 — Composable Concurrency with Ref + Deferred available at Vimeo

def consumer(done: Deferred[IO, Unit]) = for {
	c <- Consumer.setup
	_ <- done.complete(())
	msg <- c.read
	_ <- IO(println(s"Received $msg"))
} yield ()

def producer(done: Deferred[IO, Unit]) = for {
	p <- Producer.setup()
	_ <- done.get
	msg = "Msg A"
	_ <- p.write(msg)
	_ <- IO(println(s"Sent $msg"))
} yield ()

def prog = for {
  d <- Deferred[IO, Unit]
  _ <- consumer(d).start
  _ <- producer(d).start
} yield ()
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

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«Scala-».

« Scala».