Scala中的2套產品的交叉產品

Question

val cross = (for (x<-setA; y<-setB) yield (x,y)) 

val cross2 = (setA flatMap (x => setB map ((x,_))) 

是否有一種更優雅的方式可以通過跨產品運營商或其他方式做到這一點？ E.g：

val cross3 = setA cross setB 

Answer 1

import scala.collection.Set 

class 
Crossable[E1](es1: Traversable[E1]) 
{ 
    def 
    ×[E2](es2: Traversable[E2]): Traversable[(E1, E2)] = 
     for (e1 <- es1; e2 <- es2) yield (e1, e2) 

    def 
    cross[E2](es2: Traversable[E2]): Traversable[(E1, E2)] = 
     for (e1 <- es1; e2 <- es2) yield (e1, e2) 
} 


object 
Crossable 
{ 
    implicit 
    def 
    trav2Crossable[E1](es1: Traversable[E1]): Crossable[E1] = 
     new Crossable[E1](es1) 
} 


object 
CrossableTest 
{ 
    def 
    main(args: Array[String]): Unit = { 
     import Crossable.trav2Crossable 

     val es1 = Set(1, 2, 3) 
     val es2 = List("a", "b", "c") 

     (es1 × es2) foreach(printf(" %s%n", _)) 
    } 
} 

% scala -cp . CrossableTest 
    (1,c) 
    (2,b) 
    (3,a) 
    (2,a) 
    (1,a) 
    (3,b) 
    (3,c) 
    (1,b) 
    (2,c)