scala> //定義一個(gè)方法

scala> def m(x:Int) = 2*x
m: (x: Int)Int

scala> //定義一個(gè)函數(shù)

scala> val f = (x:Int) => 2*x
f: Int => Int = <function1>

scala> //方法不能作為最終表達(dá)式出現(xiàn)

scala> m
<console>:9: error: missing arguments for method m;
follow this method with `_‘ if you want to treat it as a partially applied function

函數(shù)是一個(gè)對(duì)象，繼承自FuctionN，函數(shù)對(duì)象有curried,equals,isInstanceOf,toString這些方法。
而方法不具有這些特性。如果想把方法轉(zhuǎn)換成一個(gè)函數(shù)，可以用方法名跟上下劃線的方式.