「=>」scalaでの意味

現在知られている基本は匿名関数定義と関数タイプ宣言に関係し、case文での使用
=> 
1、匿名関数定義、左がパラメータ右が関数実装体(x:Int)=>{}
2、関数タイプの
宣言、左はパラメータタイプ、右はメソッド戻り値タイプ(Int)=>(Int)
3、
By-name-parameter      f(p :=>Int)
2との違い
参考:scala By-name-parameterとFunction typeの違い
4、 case
文の中case x => y
 
 
しかしstackoverflowではこの方面についての議論が多いので、ここで記録します.
 
例えばhttp://stackoverflow.com/questions/6951895/what-does-and-mean-in-scalaの回答:
 
=> has several meanings in Scala, all related to its mathematical meaning as implication.

In a value, it introduces a function literal, or lambda. e.g. the bit inside the curly braces in  List(1,2,3).map { (x: Int) => x * 2 }（ ）

In a type, with symbols on both sides of the arrow (e.g.  A => T ,  (A,B) => T ,  (A,B,C) => T , etc.) it's sugar for  Function<n>[A[,B,...],T] , that is, a function that takes parameters of type  A[,B...] , and returns a value of type  T .(関数タイプ定義)

Empty parens on the left hand side (e.g.  () => T ) indicate that the function takes no parameters (also sometimes called a "thunk");

Empty parens on the right hand side denote that it returns  () —the sole value of type  Unit , whose name can also be written  () —confused yet? :) A function that returns Unit is also known as a procedure, normally a method that's called only for its side effect.

In the type declaration for a method or function parameter, with no symbol on the left hand side (e.g.  def f(param: => T) ) it's a "by-name parameter", meaning that is evaluated every time it's used within the body of the function, and not before. Ordinary "by-value"parameters are evaluated before entry into the function/method.(関数タイプ定義)

In a  case  clause, they separate the pattern (and optional guard) from the result expression, e.g.  case x => y .(case文)

 
 
 
 
http://stackoverflow.com/questions/6951895/what-does-and-mean-in-scala
 
http://stackoverflow.com/questions/7888944/scala-punctuation-aka-symbols-and-operators