<-的使用

<-用于for循环中，for (i <- 表达式)例如

scala> val n = 5
n: Int = 5

scala> for (i <- 1 to n)
     | println(i)
1
2
3
4
5

->的使用

用《Scala for the Impatient》中的一段话描述

In Scala, a map is a collection of pairs. A pair is simply a grouping of two values, not necessarily of the same type, such as("Alice", 10).
The -> operator makes a pair.
The value of "Alice" -> 10 is
("Alice", 10)

所以，一般->用来生成map中的key/value pairs，例如

scala> val scores = Map("Alice" -> 10, "Bob" ->3, "Cindy" -> 8)
scores: scala.collection.immutable.Map[String,Int] = Map(Alice -> 10, Bob -> 3, Cindy -> 8)

scala> val newSources = scores + ("Bob" -> 10, "Fred" -> 7)
newSources: scala.collection.immutable.Map[String,Int] = Map(Alice -> 10, Bob -> 10, Cindy -> 8, Fred -> 7)