如何從scala中的字符串值生成規則？

Question

我想從字符串制定規則。例如， 我的字符串是：

Ball Cat Egg 
Cat Egg 
Apple Cat 
Ball Egg 
Ball Cat 

我想要的規則，

Ball -> Cat Egg 
Cat -> Ball Egg 
Egg -> Ball Cat 
Ball Cat -> Egg 
Cat Egg -> Ball 
Ball Egg -> Cat 
Cat -> Egg 
Egg -> Cat 
Apple -> Cat 
Cat -> Apple 
Ball -> Egg 
Egg -> Ball 
Ball -> Cat 
Cat -> Ball 

Answer 1

scala> val strs = Seq("BCE", "CE", "AC", "BE", "BC") 
strs: Seq[String] = List(BCE, CE, AC, BE, BC) 

scala> val rules = for(s <- strs;i <- 1 to s.size-1;p <- s combinations i) yield p -> s.diff(p) 
rules: Seq[(String, String)] = 
List((B,CE), 
    (C,BE), 
    (E,BC), 
    (BC,E), 
    (BE,C), 
    (CE,B), 
    (C,E), 
    (E,C), 
    (A,C), 
    (C,A), 
    (B,E), 
    (E,B), 
    (B,C), 
    (C,B)) 

編輯這裏是新問題的代碼：

scala> case class Rule(src: Seq[String], dst: Seq[String]) { 
    | override def toString = s"${src.mkString(" ")} -> ${dst.mkString(" ")}" 
    | } 
defined class Rule 

scala> val strs = Seq("Ball Cat Egg", "Cat Egg", "Apple Cat", "Ball Egg", "Ball Cat") 
strs: Seq[String] = List(Ball Cat Egg, Cat Egg, Apple Cat, Ball Egg, Ball Cat) 

scala> val rules = for(s <- strs;l = s.split(" ");i <- 1 to l.size-1;p <- l combinations i) 
        yield Rule(p, l diff p) 
rules: Seq[Rule] = List(Ball -> Cat Egg, Cat -> Ball Egg, Egg -> Ball Cat, 
         Ball Cat -> Egg, Ball Egg -> Cat, Cat Egg -> Ball, 
         Cat -> Egg, Egg -> Cat, Apple -> Cat, Cat -> Apple, 
         Ball -> Egg, Egg -> Ball, Ball -> Cat, Cat -> Ball)