@@ -19,7 +19,7 @@ language: "zh-cn"
1919| <span class =" label success " >Good</span > ` val x = 5 ` <br > <span class =" label important " >Bad</span > ` x=6 ` | 常量 |
2020| ` var x: Double = 5 ` | 显式类型 |
2121| <span id =" functions " class =" h2 " >函数</span > | |
22- | <span class =" label success " >Good</span > ` def f(x: Int) = { x*x } ` <br > <span class =" label important " >Bad</span > ` def f(x: Int) { x*x } ` | 定义函数 <br > 隐含的错误 : 不加“=”号将会是一段返回Unit类型的过程，这将会导致意想不到的错误。 |
22+ | <span class =" label success " >Good</span > ` def f(x: Int) = { x*x } ` <br > <span class =" label important " >Bad</span > ` def f(x: Int) { x*x } ` | 定义函数 <br > 潜在风险 : 不加“=”号将会是一段返回Unit类型的过程，这将会导致意想不到的错误。 |
2323| <span class =" label success " >Good</span > ` def f(x: Any) = println(x) ` <br > <span class =" label important " >Bad</span > ` def f(x) = println(x) ` | 定义函数 <br > 语法错误: 每个参数都需要指定类型。 |
2424| ` type R = Double ` | 类型别名 |
2525| ` def f(x: R) ` vs.<br > ` def f(x: => R) ` | 传值调用 <br > 传名调用 （惰性参数） |
@@ -46,7 +46,7 @@ language: "zh-cn"
4646| <span id =" data_structures " class =" h2 " >数据结构</span > | |
4747| ` (1,2,3) ` | 元组字面量 (` Tuple3 ` ) |
4848| ` var (x,y,z) = (1,2,3) ` | 解构绑定：通过模式匹配来解构元组。 |
49- | <span class =" label important " >Bad</span >` var x,y,z = (1,2,3) ` | 隐含的错误 ：整个元组被赋值给了每一个变量。 |
49+ | <span class =" label important " >Bad</span >` var x,y,z = (1,2,3) ` | 潜在风险 ：整个元组被赋值给了每一个变量。 |
5050| ` var xs = List(1,2,3) ` | 列表 (不可变)。 |
5151| ` xs(2) ` | 用括号索引 ([ slides] ( http://www.slideshare.net/Odersky/fosdem-2009-1013261/27 ) ) |
5252| ` 1 :: List(2,3) ` | Cons（构成） |
@@ -58,12 +58,12 @@ language: "zh-cn"
5858| ` while (x < 5) { println(x); x += 1} ` | while循环 |
5959| ` do { println(x); x += 1} while (x < 5) ` | do while循环 |
6060| ` import scala.util.control.Breaks._ ` <br >` breakable { ` <br >` for (x <- xs) { ` <br >` if (Math.random < 0.1) break ` <br >` } ` <br >` } ` | break. ([ slides] ( http://www.slideshare.net/Odersky/fosdem-2009-1013261/21 ) ) |
61- | ` for (x <- xs if x%2 == 0) yield x*10 ` _ 等价于_ <br >` xs.filter(_%2 == 0).map(_*10) ` | for 推导式 : filter/map |
62- | ` for ((x,y) <- xs zip ys) yield x*y ` _ 等价于_ <br >` (xs zip ys) map { case (x,y) => x*y } ` | for 推导式 : 解构绑定 |
63- | ` for (x <- xs; y <- ys) yield x*y ` _ 等价于_ <br >` xs flatMap {x => ys map {y => x*y}} ` | for 推导式 : 叉乘 |
64- | ` for (x <- xs; y <- ys) { ` <br > ` println("%d/%d = %.1f".format(x, y, x/y.toFloat)) ` <br >` } ` | for 推导式 : 不可避免的格式<br >[ sprintf-style] ( http://java.sun.com/javase/6/docs/api/java/util/Formatter.html#syntax ) |
65- | ` for (i <- 1 to 5) { ` <br > ` println(i) ` <br >` } ` | for 推导式 : 包括上边界的遍历 |
66- | ` for (i <- 1 until 5) { ` <br > ` println(i) ` <br >` } ` | for 推导式 : 忽略上边界的遍历 |
61+ | ` for (x <- xs if x%2 == 0) yield x*10 ` _ 等价于_ <br >` xs.filter(_%2 == 0).map(_*10) ` | for 表达式 : filter/map |
62+ | ` for ((x,y) <- xs zip ys) yield x*y ` _ 等价于_ <br >` (xs zip ys) map { case (x,y) => x*y } ` | for 表达式 : 解构绑定 |
63+ | ` for (x <- xs; y <- ys) yield x*y ` _ 等价于_ <br >` xs flatMap {x => ys map {y => x*y}} ` | for 表达式 : 叉乘 |
64+ | ` for (x <- xs; y <- ys) { ` <br > ` println("%d/%d = %.1f".format(x, y, x/y.toFloat)) ` <br >` } ` | for 表达式 : 不可避免的格式<br >[ sprintf-style] ( http://java.sun.com/javase/6/docs/api/java/util/Formatter.html#syntax ) |
65+ | ` for (i <- 1 to 5) { ` <br > ` println(i) ` <br >` } ` | for 表达式 : 包括上边界的遍历 |
66+ | ` for (i <- 1 until 5) { ` <br > ` println(i) ` <br >` } ` | for 表达式 : 忽略上边界的遍历 |
6767| <span id =" pattern_matching " class =" h2 " >模式匹配</span > | |
6868| <span class =" label success " >Good</span > ` (xs zip ys) map { case (x,y) => x*y } ` <br > <span class =" label important " >Bad</span > ` (xs zip ys) map( (x,y) => x*y ) ` | 在函数的参数中使用模式匹配的例子。 |
6969| <span class =" label important " >Bad</span ><br >` val v42 = 42 ` <br >` Some(3) match { ` <br >` case Some(v42) => println("42") ` <br >` case _ => println("Not 42") ` <br >` } ` | "v42" 被解释为可以匹配任何Int类型值的名称，打印输出"42"。 |
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