@@ -14,25 +14,25 @@ languages: [zh-cn]
1414| <span id =" variables " class =" h2 " >变量</span > | |
1515| ` var x = 5 ` | 变量 |
1616| <span class =" label success " >Good</span > ` val x = 5 ` <br > <span class =" label important " >Bad</span > ` x=6 ` | 常量 |
17- | ` var x: Double = 5 ` | 指定数据类型 |
17+ | ` var x: Double = 5 ` | 显式类型 |
1818| <span id =" functions " class =" h2 " >函数</span > | |
1919| <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 > 隐藏错误: 没有“=”程序会返回Unit类型，这将会引起重大灾难。 |
2020| <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。 |
2121| ` type R = Double ` | 类型别名 |
22- | ` def f(x: R) ` vs.<br > ` def f(x: => R) ` | 按值调用 <br > 按名称调用 （惰性参数） |
22+ | ` def f(x: R) ` vs.<br > ` def f(x: => R) ` | 传值调用 <br > 传名调用 （惰性参数） |
2323| ` (x:R) => x*x ` | 匿名函数 |
2424| ` (1 to 5).map(_*2) ` vs.<br > ` (1 to 5).reduceLeft( _+_ ) ` | 匿名函数: 下划线是arg参数的占位符。 |
2525| ` (1 to 5).map( x => x*x ) ` | 匿名函数: 必须命名以后才可以使用一个arg参数两次。 |
2626| <span class =" label success " >Good</span > ` (1 to 5).map(2*) ` <br > <span class =" label important " >Bad</span > ` (1 to 5).map(*2) ` | 匿名函数: 边界前缀方法，理智的人都用` 2*_ ` 。 |
27- | ` (1 to 5).map { x => val y=x*2; println(y); y } ` | 匿名函数: 上个方法的程序块风格 。 |
27+ | ` (1 to 5).map { x => val y=x*2; println(y); y } ` | 匿名函数: 程序块风格，返回的是最后一个表达式 。 |
2828| ` (1 to 5) filter {_%2 == 0} map {_*2} ` | 匿名函数: 管道风格（或者叫括号风格）。 |
2929| ` def compose(g:R=>R, h:R=>R) = (x:R) => g(h(x)) ` <br > ` val f = compose({_*2}, {_-1}) ` | 匿名函数: 要传入多个程序块的话，需要外部括号。 |
3030| ` val zscore = (mean:R, sd:R) => (x:R) => (x-mean)/sd ` | 柯里化, 很显然的语法。 |
3131| ` def zscore(mean:R, sd:R) = (x:R) => (x-mean)/sd ` | 柯里化, 很显然的语法。 |
32- | ` def zscore(mean:R, sd:R)(x:R) = (x-mean)/sd ` | 柯里化，语法糖，然并卵 。 |
33- | ` val normer = zscore(7, 0.4) _ ` | 需要接上下划线才能得到偏微商 （只适用于语法糖版本）。 |
32+ | ` def zscore(mean:R, sd:R)(x:R) = (x-mean)/sd ` | 柯里化，语法糖。 |
33+ | ` val normer = zscore(7, 0.4) _ ` | 需要在后面加下划线来部分应用 （只适用于语法糖版本）。 |
3434| ` def mapmake[T](g:T=>T)(seq: List[T]) = seq.map(g) ` | 泛型 |
35- | ` 5.+(3); 5 + 3 ` <br > ` (1 to 5) map (_*2) ` | 前缀语法糖 |
35+ | ` 5.+(3); 5 + 3 ` <br > ` (1 to 5) map (_*2) ` | 中缀语法糖 |
3636| ` def sum(args: Int*) = args.reduceLeft(_+_) ` | 可变参数 |
3737| <span id =" packages " class =" h2 " >包</span > | |
3838| ` import scala.collection._ ` | 通配符导入 |
@@ -41,46 +41,46 @@ languages: [zh-cn]
4141| ` import java.util.{Date => _, _} ` | 导入java.util包里除Date之外的所有文件. |
4242| ` package pkg ` _ at start of file_ <br > ` package pkg { ... } ` | 声明一个包 |
4343| <span id =" data_structures " class =" h2 " >数据结构</span > | |
44- | ` (1,2,3) ` | 元组 (` Tuple3 ` ) |
44+ | ` (1,2,3) ` | 元组字面量 (` Tuple3 ` ) |
4545| ` var (x,y,z) = (1,2,3) ` | 解构绑定：通过模式匹配来解构元组。 |
4646| <span class =" label important " >Bad</span >` var x,y,z = (1,2,3) ` | 隐藏错误：每一个变量都被赋值了整个元组。 |
4747| ` var xs = List(1,2,3) ` | 列表 (不可变). |
4848| ` xs(2) ` | 用括号索引 ([ slides] ( http://www.slideshare.net/Odersky/fosdem-2009-1013261/27 ) ) |
49- | ` 1 :: List(2,3) ` | 在列表开头添加元素 |
50- | ` 1 to 5 ` _ same as _ ` 1 until 6 ` <br > ` 1 to 10 by 2 ` | 范围 （语法糖） |
51- | ` () ` _ (empty parens )_ | Unit类型的专有成员 (相当于 C/Java 里的void). |
49+ | ` 1 :: List(2,3) ` | cons |
50+ | ` 1 to 5 ` _ 等价于 _ ` 1 until 6 ` <br > ` 1 to 10 by 2 ` | Range类型 （语法糖） |
51+ | ` () ` _ (空括号 )_ | Unit类型的专有成员 (相当于 C/Java 里的void). |
5252| <span id =" control_constructs " class =" h2 " >控制结构</span > | |
5353| ` if (check) happy else sad ` | 条件 |
5454| ` if (check) happy ` _ same as_ <br > ` if (check) happy else () ` | 条件（语法糖） |
5555| ` while (x < 5) { println(x); x += 1} ` | while循环 |
5656| ` do { println(x); x += 1} while (x < 5) ` | do while循环 |
5757| ` 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 ) ) |
58- | ` for (x <- xs if x%2 == 0) yield x*10 ` _ same as _ <br >` xs.filter(_%2 == 0).map(_*10) ` | for循环: filter/map |
59- | ` for ((x,y) <- xs zip ys) yield x*y ` _ same as _ <br >` (xs zip ys) map { case (x,y) => x*y } ` | for循环: 解构绑定 |
60- | ` for (x <- xs; y <- ys) yield x*y ` _ same as _ <br >` xs flatMap {x => ys map {y => x*y}} ` | for循环: 叉乘 |
61- | ` for (x <- xs; y <- ys) { ` <br > ` println("%d/%d = %.1f".format(x, y, x/y.toFloat)) ` <br >` } ` | for循环: 势在必行的格式 <br >[ sprintf-style] ( http://java.sun.com/javase/6/docs/api/java/util/Formatter.html#syntax ) |
58+ | ` for (x <- xs if x%2 == 0) yield x*10 ` _ 等价于 _ <br >` xs.filter(_%2 == 0).map(_*10) ` | for循环: filter/map |
59+ | ` for ((x,y) <- xs zip ys) yield x*y ` _ 等价于 _ <br >` (xs zip ys) map { case (x,y) => x*y } ` | for循环: 解构绑定 |
60+ | ` for (x <- xs; y <- ys) yield x*y ` _ 等价于 _ <br >` xs flatMap {x => ys map {y => x*y}} ` | for循环: 叉乘 |
61+ | ` for (x <- xs; y <- ys) { ` <br > ` println("%d/%d = %.1f".format(x, y, x/y.toFloat)) ` <br >` } ` | for循环: 不可避免的格式 <br >[ sprintf-style] ( http://java.sun.com/javase/6/docs/api/java/util/Formatter.html#syntax ) |
6262| ` for (i <- 1 to 5) { ` <br > ` println(i) ` <br >` } ` | for循环: 包括上边界的遍历 |
6363| ` for (i <- 1 until 5) { ` <br > ` println(i) ` <br >` } ` | for循环: 忽略上边界的遍历 |
6464| <span id =" pattern_matching " class =" h2 " >模式匹配</span > | |
65- | <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 ) ` | 模式匹配中，函数的参数需要使用case 。 |
65+ | <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 。 |
6666| <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"。 |
67- | <span class =" label success " >Good</span ><br >` val v42 = 42 ` <br >` Some(3) match { ` <br >`` case Some(`v42`) => println("42") `` <br >` case _ => println("Not 42") ` <br >` } ` | 有倒引号的 "\` v42\` " 被解释为已经存在的val ` v42 ` ，所以输出的是 "Not 42". |
68- | <span class =" label success " >Good</span ><br >` val UppercaseVal = 42 ` <br >` Some(3) match { ` <br >` case Some(UppercaseVal) => println("42") ` <br >` case _ => println("Not 42") ` <br >` } ` | ` UppercaseVal ` 被视作已经存在的 val，而不是一个新的模式变量，因为它是以大写字母开头的，所以` UppercaseVal ` 包含的值是 ` 3 ` , 结果输出的是 "Not 42"。|
67+ | <span class =" label success " >Good</span ><br >` val v42 = 42 ` <br >` Some(3) match { ` <br >`` case Some(`v42`) => println("42") `` <br >` case _ => println("Not 42") ` <br >` } ` | 有反引号的 "\` v42\` " 被解释为已经存在的val ` v42 ` ，所以输出的是 "Not 42". |
68+ | <span class =" label success " >Good</span ><br >` val UppercaseVal = 42 ` <br >` Some(3) match { ` <br >` case Some(UppercaseVal) => println("42") ` <br >` case _ => println("Not 42") ` <br >` } ` | ` UppercaseVal ` 被视作已经存在的 val，而不是一个新的模式变量，因为它是以大写字母开头的，所以` UppercaseVal ` 所包含的值（42）和检查的值（3）不匹配，输出 "Not 42"。|
6969| <span id =" object_orientation " class =" h2 " >面向对象</span > | |
7070| ` class C(x: R) ` _ same as_ <br >` class C(private val x: R) ` <br >` var c = new C(4) ` | 构造器参数 - 私有 |
7171| ` class C(val x: R) ` <br >` var c = new C(4) ` <br >` c.x ` | 构造器参数 - 公有 |
72- | ` class C(var x: R) { ` <br >` assert(x > 0, "positive please") ` <br >` var y = x ` <br >` val readonly = 5 ` <br >` private var secret = 1 ` <br >` def this = this(42) ` <br >` } ` | <br >类本身就是构造器 <br >声明一个公有成员变量<br >声明一个可获得但不可设置的成员变量 <br >声明一个私有变量r <br >可选构造器|
72+ | ` class C(var x: R) { ` <br >` assert(x > 0, "positive please") ` <br >` var y = x ` <br >` val readonly = 5 ` <br >` private var secret = 1 ` <br >` def this = this(42) ` <br >` } ` | <br >构造函数就是类的主体 <br >声明一个公有成员变量<br >声明一个可get但不可set的成员变量 <br >声明一个私有变量 <br >可选构造器|
7373| ` new{ ... } ` | 匿名类 |
7474| ` abstract class D { ... } ` | 定义一个抽象类。（不可创建） |
7575| ` class C extends D { ... } ` | 定义一个继承子类。 |
7676| ` class D(var x: R) ` <br >` class C(x: R) extends D(x) ` | 继承与构造器参数（愿望清单: 默认自动传参）
7777| ` object O extends D { ... } ` | 定义一个单例模式（模块化的） |
78- | ` trait T { ... } ` <br >` class C extends T { ... } ` <br >` class C extends D with T { ... } ` | 特性 <br >带有实现的接口，没有构造参数。 [ mixin-able] ({{ site.baseurl }}/tutorials/tour/mixin-class-composition.html).
79- | ` trait T1; trait T2 ` <br >` class C extends T1 with T2 ` <br >` class C extends D with T1 with T2 ` | 多重特性 |
80- | ` class C extends D { override def f = ...} ` | 必须声明函数的重载 。 |
81- | ` new java.io.File("f") ` | 创建类 。 |
82- | <span class =" label important " >Bad</span > ` new List[Int] ` <br > <span class =" label success " >Good</span > ` List(1,2,3) ` | 类型错误： 抽象类型<br >相反，习惯上：调用的“工厂“会推测类型 |
83- | ` classOf[String] ` | 类字面常量 |
78+ | ` trait T { ... } ` <br >` class C extends T { ... } ` <br >` class C extends D with T { ... } ` | 特质 <br >带有实现的接口，没有构造参数。 [ mixin-able] ({{ site.baseurl }}/tutorials/tour/mixin-class-composition.html).
79+ | ` trait T1; trait T2 ` <br >` class C extends T1 with T2 ` <br >` class C extends D with T1 with T2 ` | （混入）多个特质 |
80+ | ` class C extends D { override def f = ...} ` | 必须声明函数的重写 。 |
81+ | ` new java.io.File("f") ` | 创建对象 。 |
82+ | <span class =" label important " >Bad</span > ` new List[Int] ` <br > <span class =" label success " >Good</span > ` List(1,2,3) ` | 类型错误： 抽象类型<br >相反，习惯上：调用工厂（方法）会自动推测类型 |
83+ | ` classOf[String] ` | 类字面量 |
8484| ` x.isInstanceOf[String] ` | 类型检查 (运行时) |
8585| ` x.asInstanceOf[String] ` | 类型强制转换 (运行时) |
8686| ` x: String ` | 归属 (编译时) |
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