scala for-comprehension scala-2.7

¿Puedo usar for-comprensión/rendimiento para crear un mapa en Scala?



for-comprehension scala-2.7 (4)

¿Puedo "ceder" en un mapa?

He intentado

val rndTrans = for (s1 <- 0 to nStates; s2 <- 0 to nStates if rnd.nextDouble() < trans_probability) yield (s1 -> s2);

(y con , lugar de -> ) pero me sale el error

TestCaseGenerator.scala:42: error: type mismatch; found : Seq.Projection[(Int, Int)] required: Map[State,State] new LTS(rndTrans, rndLabeling)

Puedo ver por qué, pero no puedo ver cómo resolver esto: - /


Alternativa ( funciona en 2.7 ):

scala> Map((for(i <- 0 to 10; j <- 0 to 10) yield (i -> j)): _*) res0: scala.collection.immutable.Map[Int,Int] = Map((0,10), (5,10), (10,10), (1,10), (6,10), (9,10), (2,10), (7,10), (3,10), (8,10), (4,10))


Una solución alternativa en Scala 2.8:

Welcome to Scala version 2.8.1.r23457-b20101106033551 (Java HotSpot(TM) Client VM, Java 1.6.0_22). Type in expressions to have them evaluated. Type :help for more information. scala> import scala.collection.breakOut import scala.collection.breakOut scala> val list: List[(Int,Int)] = (for(i<-0 to 3;j<-0 to 2) yield(i->j))(breakOut) list: List[(Int, Int)] = List((0,0), (0,1), (0,2), (1,0), (1,1), (1,2), (2,0), (2,1), (2,2), (3,0), (3,1), (3,2)) scala> val map: Map[Int,Int] = (for(i<-0 to 3;j<-0 to 2) yield(i->j))(breakOut) map: Map[Int,Int] = Map((0,2), (1,2), (2,2), (3,2)) scala> val set: Set[(Int,Int)] = (for(i<-0 to 3;j<-0 to 2) yield(i->j))(breakOut) set: Set[(Int, Int)] = Set((2,2), (3,2), (0,1), (1,2), (0,0), (2,0), (3,1), (0,2), (1,1), (2,1), (1,0), (3,0)) scala>


val rndTrans = ( for { s1 <- 0 to nStates s2 <- 0 to nStates if rnd.nextDouble() < trans_probability } yield s1 -> s2 ) (collection.breakOut[Any, (Int, Int), Map[Int, Int]])


scala> (for(i <- 0 to 10; j <- 0 to 10) yield (i -> j)) toMap res1: scala.collection.immutable.Map[Int,Int] = Map((0,10), (5,10), (10,10), (1,10), (6,10), (9,10), (2,10), (7,10), (3,10), (8,10), (4,10))