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Diffstat (limited to 'spec/01-lexical-syntax.md')
| -rw-r--r-- | spec/01-lexical-syntax.md | 348 |
1 files changed, 166 insertions, 182 deletions
diff --git a/spec/01-lexical-syntax.md b/spec/01-lexical-syntax.md index 3972961f58..e26cb796c8 100644 --- a/spec/01-lexical-syntax.md +++ b/spec/01-lexical-syntax.md @@ -101,19 +101,18 @@ _ : = => <- <: <% >: # @ The Unicode operators `\u21D2` ‘$\Rightarrow$’ and `\u2190` ‘$\leftarrow$’, which have the ASCII equivalents `=>` and `<-`, are also reserved. -### Example -Here are examples of identifiers: -```scala - x Object maxIndex p2p empty_? - + `yield` αρετη _y dot_product_* - __system _MAX_LEN_ -``` +> Here are examples of identifiers: +> ```scala +> x Object maxIndex p2p empty_? +> + `yield` αρετη _y dot_product_* +> __system _MAX_LEN_ +> ``` + +<!-- --> -### Example -When one needs to access Java identifiers that are reserved words in Scala, use backquote-enclosed strings. -For instance, the statement `Thread.yield()` is illegal, since -`yield` is a reserved word in Scala. However, here's a -work-around: `` Thread.`yield`() `` +> When one needs to access Java identifiers that are reserved words in Scala, use backquote-enclosed strings. +> For instance, the statement `Thread.yield()` is illegal, since `yield` is a reserved word in Scala. +> However, here's a work-around: `` Thread.`yield`() `` ## Newline Characters @@ -205,99 +204,96 @@ A single new line token is accepted - after an [infix operator](06-expressions.html#prefix,-infix,-and-postfix-operations), if the first token on the next line can start an expression, - in front of a [parameter clause](04-basic-declarations-and-definitions.html#function-declarations-and-definitions), and -- after an [annotation](11-user-defined-annotations.html#user-defined-annotations). - -### Example - -The newline tokens between the two lines are not -treated as statement separators. - -```scala -if (x > 0) - x = x - 1 - -while (x > 0) - x = x / 2 - -for (x <- 1 to 10) - println(x) - -type - IntList = List[Int] -``` - -### Example - -```scala -new Iterator[Int] -{ - private var x = 0 - def hasNext = true - def next = { x += 1; x } -} -``` - -With an additional newline character, the same code is interpreted as -an object creation followed by a local block: - -```scala -new Iterator[Int] - -{ - private var x = 0 - def hasNext = true - def next = { x += 1; x } -} -``` - -### Example - -```scala - x < 0 || - x > 10 -``` - -With an additional newline character, the same code is interpreted as -two expressions: - -```scala - x < 0 || - - x > 10 -``` - -### Example - -```scala -def func(x: Int) - (y: Int) = x + y -``` - -With an additional newline character, the same code is interpreted as -an abstract function definition and a syntactically illegal statement: - -```scala -def func(x: Int) - - (y: Int) = x + y -``` - -### Example - -```scala -@serializable -protected class Data { ... } -``` - -With an additional newline character, the same code is interpreted as -an attribute and a separate statement (which is syntactically -illegal). - -```scala -@serializable - -protected class Data { ... } -``` +- after an [annotation](11-annotations.html#user-defined-annotations). + +> The newline tokens between the two lines are not +> treated as statement separators. +> +> ```scala +> if (x > 0) +> x = x - 1 +> +> while (x > 0) +> x = x / 2 +> +> for (x <- 1 to 10) +> println(x) +> +> type +> IntList = List[Int] +> ``` + +<!-- --> + +> ```scala +> new Iterator[Int] +> { +> private var x = 0 +> def hasNext = true +> def next = { x += 1; x } +> } +> ``` +> +> With an additional newline character, the same code is interpreted as +> an object creation followed by a local block: +> +> ```scala +> new Iterator[Int] +> +> { +> private var x = 0 +> def hasNext = true +> def next = { x += 1; x } +> } +> ``` + +<!-- --> + +> ```scala +> x < 0 || +> x > 10 +> ``` +> +> With an additional newline character, the same code is interpreted as +> two expressions: +> +> ```scala +> x < 0 || +> +> x > 10 +> ``` + +<!-- --> + +> ```scala +> def func(x: Int) +> (y: Int) = x + y +> ``` +> +> With an additional newline character, the same code is interpreted as +> an abstract function definition and a syntactically illegal statement: +> +> ```scala +> def func(x: Int) +> +> (y: Int) = x + y +> ``` + +<!-- --> + +> ```scala +> @serializable +> protected class Data { ... } +> ``` +> +> With an additional newline character, the same code is interpreted as +> an attribute and a separate statement (which is syntactically illegal). +> +> ```scala +> @serializable +> +> protected class Data { ... } +> ``` ## Literals @@ -351,11 +347,9 @@ is _pt_. The numeric ranges given by these types are: |`Short` | $-2\^{15}$ to $2\^{15}-1$| |`Char` | $0$ to $2\^{16}-1$ | -### Example - -```scala -0 21 0xFFFFFFFF -42L -``` +> ```scala +> 0 21 0xFFFFFFFF -42L +> ``` ### Floating Point Literals @@ -379,20 +373,18 @@ If a floating point literal in a program is followed by a token starting with a letter, there must be at least one intervening whitespace character between the two tokens. -### Example +> ```scala +> 0.0 1e30f 3.14159f 1.0e-100 .1 +> ``` -```scala -0.0 1e30f 3.14159f 1.0e-100 .1 -``` +<!-- --> -### Example +> The phrase `1.toString` parses as three different tokens: +> the integer literal `1`, a `.`, and the identifier `toString`. -The phrase `1.toString` parses as three different tokens: -the integer literal `1`, a `.`, and the identifier `toString`. +<!-- --> -### Example - -`1.` is not a valid floating point literal because the mandatory digit after the `.` is missing. +> `1.` is not a valid floating point literal because the mandatory digit after the `.` is missing. ### Boolean Literals @@ -413,11 +405,9 @@ A character literal is a single character enclosed in quotes. The character is either a printable unicode character or is described by an [escape sequence](#escape-sequences). -### Example - -```scala -'a' '\u0041' '\n' '\t' -``` +> ```scala +> 'a' '\u0041' '\n' '\t' +> ``` Note that `'\u000A'` is _not_ a valid character literal because Unicode conversion is done before literal parsing and the Unicode @@ -439,12 +429,10 @@ contains a double quote character, it must be escaped, i.e. `"\""`. The value of a string literal is an instance of class `String`. -### Example - -```scala -"Hello,\nWorld!" -"This string contains a \" character." -``` +> ```scala +> "Hello,\nWorld!" +> "This string contains a \" character." +> ``` #### Multi-Line String Literals @@ -461,45 +449,43 @@ must not necessarily be printable; newlines or other control characters are also permitted. Unicode escapes work as everywhere else, but none of the escape sequences [here](#escape-sequences) are interpreted. -### Example - -```scala - """the present string - spans three - lines.""" -``` - -This would produce the string: - -```scala -the present string - spans three - lines. -``` - -The Scala library contains a utility method `stripMargin` -which can be used to strip leading whitespace from multi-line strings. -The expression - -```scala - """the present string - |spans three - |lines.""".stripMargin -``` - -evaluates to - -```scala -the present string -spans three -lines. -``` - -Method `stripMargin` is defined in class -[scala.collection.immutable.StringLike](http://www.scala-lang.org/api/current/#scala.collection.immutable.StringLike). -Because there is a predefined -[implicit conversion](06-expressions.html#implicit-conversions) from `String` to -`StringLike`, the method is applicable to all strings. +> ```scala +> """the present string +> spans three +> lines.""" +> ``` +> +> This would produce the string: +> +> ```scala +> the present string +> spans three +> lines. +> ``` +> +> The Scala library contains a utility method `stripMargin` +> which can be used to strip leading whitespace from multi-line strings. +> The expression +> +> ```scala +> """the present string +> |spans three +> |lines.""".stripMargin +> ``` +> +> evaluates to +> +> ```scala +> the present string +> spans three +> lines. +> ``` +> +> Method `stripMargin` is defined in class +> [scala.collection.immutable.StringLike](http://www.scala-lang.org/api/current/#scala.collection.immutable.StringLike). +> Because there is a predefined +> [implicit conversion](06-expressions.html#implicit-conversions) from `String` to +> `StringLike`, the method is applicable to all strings. ### Escape Sequences @@ -587,15 +573,13 @@ The scanner switches from XML mode to Scala mode if either Note that no Scala tokens are constructed in XML mode, and that comments are interpreted as text. -### Example - -The following value definition uses an XML literal with two embedded -Scala expressions: - -```scala -val b = <book> - <title>The Scala Language Specification</title> - <version>{scalaBook.version}</version> - <authors>{scalaBook.authors.mkList("", ", ", "")}</authors> - </book> -``` +> The following value definition uses an XML literal with two embedded +> Scala expressions: +> +> ```scala +> val b = <book> +> <title>The Scala Language Specification</title> +> <version>{scalaBook.version}</version> +> <authors>{scalaBook.authors.mkList("", ", ", "")}</authors> +> </book> +> ``` |