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目前仅知道和匿名函数有关
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不过stackoverflow?上关于这方面的讨论挺多的，故在此记录一下
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比如来自?http://stackoverflow.com/questions/6951895/what-does-and-mean-in-scala?的一位的回复：
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=>?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.
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.
In a?case?clause, they separate the pattern (and optional guard) from the result expression, e.g.?case x => y.
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http://stackoverflow.com/questions/6951895/what-does-and-mean-in-scala
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http://stackoverflow.com/questions/7888944/scala-punctuation-aka-symbols-and-operators
原文：http://zhouchaofei2010.iteye.com/blog/2251731