@ -46,7 +46,7 @@
< div class = "book" data-level = "3.2" data-basepath = ".." data-revision = "1402617910282 " >
< div class = "book" data-level = "3.2" data-basepath = ".." data-revision = "1402634093001 " >
< div class = "book-header" >
<!-- Actions Left -->
< a href = "#" class = "btn pull-left toggle-summary" aria-label = "Toggle summary" > < i class = "fa fa-align-justify" > < / i > < / a >
@ -657,10 +657,11 @@
< p > < a name = "literals" > < / a > < / p >
< h2 id = "-" > 字面量< / h2 >
< p > 字面值表示整型、浮点型数字或文本类型的值，举例如下：< / p >
< pre > < code > 42 // 整型字面量
< pre > < code class = "lang-swift" > 42 // 整型字面量
3.14159 // 浮点型字面量
" Hello, world!" // 文本型字面量
< / code > < / pre > < blockquote >
< / code > < / pre >
< blockquote >
< p > 字面量语法< / p >
< p > < em > literal< / em > → < a href = "https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/Swift_Programming_Language/LexicalStructure.html#//apple_ref/swift/grammar/integer-literal" target = "_blank" > integer-literal < / a > | < a href = "https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/Swift_Programming_Language/LexicalStructure.html#//apple_ref/swift/grammar/floating-point-literal" target = "_blank" > floating-point-literal< / a > < a href = "https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/Swift_Programming_Language/LexicalStructure.html#//apple_ref/swift/grammar/string-literal" target = "_blank" > string-literal < / a > < / p >
< / blockquote >
@ -669,9 +670,10 @@
< p > 十进制字面量包含数字 < code > 0< / code > 至 < code > 9< / code > 。二进制字面量只包含 < code > 0< / code > 或 < code > 1< / code > ，八进制字面量包含数字 < code > 0< / code > 至 < code > 7< / code > ，十六进制字面量包含数字 < code > 0< / code > 至 < code > 9< / code > 以及字母 < code > A< / code > 至 < code > F< / code > （大小写均可）。< / p >
< p > 负整数的字面量在数字前加减号 < code > -< / code > ，比如 < code > -42< / code > 。< / p >
< p > 允许使用下划线 < code > _< / code > 来增加数字的可读性，下划线不会影响字面量的值。整型字面量也可以在数字前加 < code > 0< / code > ，同样不会影响字面量的值。< / p >
< pre > < code > 1000_000 // 等于 1000000
< pre > < code class = "lang-swift" > 1000_000 // 等于 1000000
005 // 等于 5
< / code > < / pre > < p > 除非特殊指定，整型字面量的默认类型为 Swift 标准库类型中的 < code > Int< / code > 。Swift 标准库还定义了其他不同长度以及是否带符号的整数类型，请参考 < a href = "https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/Swift_Programming_Language/TheBasics.html#//apple_ref/doc/uid/TP40014097-CH5-XID_411" target = "_blank" > 整数类型< / a > 。< / p >
< / code > < / pre >
< p > 除非特殊指定，整型字面量的默认类型为 Swift 标准库类型中的 < code > Int< / code > 。Swift 标准库还定义了其他不同长度以及是否带符号的整数类型，请参考 < a href = "https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/Swift_Programming_Language/TheBasics.html#//apple_ref/doc/uid/TP40014097-CH5-XID_411" target = "_blank" > 整数类型< / a > 。< / p >
< blockquote >
< p > 整型字面量语法< / p >
< p > < em > integer-literal< / em > → < a href = "https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/Swift_Programming_Language/LexicalStructure.html#//apple_ref/swift/grammar/binary-literal" target = "_blank" > binary-literal < / a > < / p >
@ -703,9 +705,10 @@
< p > 十六进制浮点型字面量（< em > hexadecimal floating-point literals< / em > ）由前缀 < code > 0x< / code > 后跟可选的十六进制小数部分以及十六进制指数部分组成。十六进制小数部分由小数点后跟十六进制数字串组成。指数部分由大写或小写字母 < code > p< / code > 后跟十进制数字串组成，这串数字表示 < code > p< / code > 之前的数量乘以 2 的几次方。例如：< code > 0xFp2< / code > 表示 < code > 15 ⨉ 2^2< / code > ，也就是 < code > 60< / code > ；同样，< code > 0xFp-2< / code > 表示 < code > 15 ⨉ 2^-2< / code > ，也就是 < code > 3.75< / code > 。< / p >
< p > 与整型字面量不同，负的浮点型字面量由一元运算符减号 < code > -< / code > 和浮点型字面量组成，例如 < code > -42.0< / code > 。这代表一个表达式，而不是一个浮点整型字面量。< / p >
< p > 允许使用下划线 < code > _< / code > 来增强可读性，下划线不会影响字面量的值。浮点型字面量也可以在数字前加 < code > 0< / code > ，同样不会影响字面量的值。< / p >
< pre > < code > 10_000.56 // 等于 10000.56
< pre > < code class = "lang-swift" > 10_000.56 // 等于 10000.56
005000.76 // 等于 5000.76
< / code > < / pre > < p > 除非特殊指定，浮点型字面量的默认类型为 Swift 标准库类型中的 < code > Double< / code > ， < code > Float< / code > 类型， < / p >
< / code > < / pre >
< p > 除非特殊指定，浮点型字面量的默认类型为 Swift 标准库类型中的 < code > Double< / code > ， < code > Float< / code > 类型， < / p >
< blockquote >
< p > 浮点型字面量语法< / p >
< p > < em > floating-point-literal< / em > → < a href = "https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/Swift_Programming_Language/LexicalStructure.html#//apple_ref/swift/grammar/decimal-literal" target = "_blank" > decimal-literal< / a > < a href = "https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/Swift_Programming_Language/LexicalStructure.html#//apple_ref/swift/grammar/decimal-fraction" target = "_blank" > decimal-fraction < / a > < em > opt< / em > < a href = "https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/Swift_Programming_Language/LexicalStructure.html#//apple_ref/swift/grammar/decimal-exponent" target = "_blank" > decimal-exponent < / a > < em > opt < / em > < / p >
@ -741,11 +744,12 @@
< p > 后跟的数字表示一个 Unicode 码点。< / p >
< p > 文本型字面量允许在反斜线小括号 < code > \()< / code > 中插入表达式的值。插入表达式（< em > interpolated expression< / em > ）不能包含未转义的双引号 < code > " < / code > 、反斜线 < code > \< / code > 、回车符或者换行符。表达式值的类型必须在 < em > String< / em > 类中有对应的初始化方法。< / p >
< p > 例如，以下所有文本型字面量的值相同：< / p >
< pre > < code > " 1 2 3"
< pre > < code class = "lang-swift" > " 1 2 3"
" 1 2 \(3)"
" 1 2 \(1 + 2)"
var x = 3; " 1 2 \(x)"
< / code > < / pre > < p > 文本型字面量的默认类型为 < code > String< / code > 。组成字符串的字符类型为 < code > Character< / code > 。更多有关 < code > String< / code > 和 < code > Character< / code > 的信息请参照 < a href = "https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/Swift_Programming_Language/StringsAndCharacters.html#//apple_ref/doc/uid/TP40014097-CH7-XID_368" target = "_blank" > 字符串和字符< / a > 。< / p >
< / code > < / pre >
< p > 文本型字面量的默认类型为 < code > String< / code > 。组成字符串的字符类型为 < code > Character< / code > 。更多有关 < code > String< / code > 和 < code > Character< / code > 的信息请参照 < a href = "https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/Swift_Programming_Language/StringsAndCharacters.html#//apple_ref/doc/uid/TP40014097-CH7-XID_368" target = "_blank" > 字符串和字符< / a > 。< / p >
< blockquote >
< p > 文本型字面量语法< / p >
< p > < em > string-literal< / em > → < strong > " < / strong > < a href = "https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/Swift_Programming_Language/LexicalStructure.html#//apple_ref/swift/grammar/quoted-text" target = "_blank" > quoted-text< / a > < strong > " < / strong > < / p >
numbbbbb