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F#:什么是有效的前缀运算符?

Joel Mueller · 技术社区 · 14 年前

let (~--) (str:string) = [str];;
-----^^^

stdin(4,6): error FS1208: Invalid operator definition. 
Prefix operator definitions must use a valid prefix operator name.

编辑:

Brian的链接包括以下有效前缀运算符列表:

! (or repetitions of !)
~ (or repetitions of ~)
+
-
+.
-.
%
%%
&
&&

我下面的链接只列出了这些运算符:

~
!
?

快速测试表明MSDN文档似乎与语言规范不符。谢谢,Brian。

3 回复 | 直到 14 年前

itowlson 14 年前

http://research.microsoft.com/en-us/um/cambridge/projects/fsharp/manual/spec.html#_Toc245030784

说明了规则。我在下面引用了一些(另请参见

http://msdn.microsoft.com/en-us/library/dd233228(VS.100).aspx

以下符号操作标记可用于形成表达式:

infix-op :=
    or || & && <OP >OP $OP = |OP &OP ^OP :: -OP +OP *OP /OP %OP 
    **OP

infix-or=prefix-op :=
    -OP +OP % %% & &&

prefix-op :=
    ! (or repetitions of !)
    ~ (or repetitions of ~) 
    +
    -
    +.
    -.
    %
    %%
    &
    &&

由以下内容组成的运算符始终是前缀运算符:

重复的!
重复~

不允许使用以这些字符开头的其他运算符。

运算符+、-、+、-、%、&&&和可以用作前缀和中缀运算符。当用作前缀运算符时,这些运算符有一个带有~前缀的隐式运算符名称。例如,-x被解析为运算符~-对表达式x的应用程序。在为这些前缀运算符提供定义时,也使用此名称:

这意味着这些前缀运算符是通过添加~字符来定义的:

// For a complete redefinition of the operator:
let (~+) x = x

// For defining the operator on a type:
type C(n:int) =
    let n = n % 7
    member x.N = n
    static member (~+) (x:C) = x
    static member (~-) (x:C) = C(-n)
    static member (+) (x1:C,x2:C) = C(x1.N+x2.N)
    static member (-) (x1:C,x2:C) = C(x1.N-x2.N)

Olaf 9 年前

前缀运算符有两种类型:tilde前缀运算符和bang前缀运算符。颚化符前缀运算符以颚化符“~”开头,bang前缀运算符以bang“!”开头。主要区别在于,在应用波浪号前缀运算符时,忽略了波浪号字符。

颚化符前缀运算符

以波浪号为前缀的运算符以波浪号“~”开头,后跟以下内容之一:

波浪号前缀运算符也可以构建为任意数量波浪号的列表:
~~, ~~~, ~~~~, ~~~~~, ...

应用运算符时,必须省略波浪形,除非它是波浪形蛇。

âââââââââââââââ¦âââââââââââââ¦âââââââââââââââââââââââââââ
â declaration â   usage    â         remark           â
â ââââââââââââââ¬âââââââââââââ¬âââââââââââââââââââââââââââ£
â ~~          â ~~         â                          â
â ~~~         â ~~~        â                          â
â ~~~~~~~~~   â ~~~~~~~~~  â or any number of tildes  â
â ~+          â +          â                          â
â ~+.         â +.         â                          â
â ~-          â -          â                          â
â ~-.         â -.         â                          â
â ~%          â %          â                          â
â ~%%         â %%         â                          â
â ~&          â &          â                          â
â ~&&         â &&         â                          â
âââââââââââââââ©âââââââââââââ©âââââââââââââââââââââââââââ

Bang前缀运算符

带bang前缀的运算符以bang“!”开头后跟以下字符的任意组合:

此规则的例外是“!=”。前缀运算符不能以此组合开头。

ââââââââââââââââ¦âââââââââââââââ
â declaration  â    usage     â
â âââââââââââââââ¬âââââââââââââââ£
â !!           â !!           â
â !%           â !%           â
â !&           â !&           â
â !*           â !*           â
â !+           â !+           â
â !.           â !.           â
â !/           â !/           â
â !<           â !<           â
â !>           â !>           â
â !@           â !@           â
â !^           â !^           â
â !|           â !|           â
â !~           â !~           â
â !?           â !?           â
â !@=@>        â !@=@>        â
â !!!/<=>@!!!* â !!!/<=>@!!!* â
ââââââââââââââââ©âââââââââââââââ

type SomeString = SomeString of string

let ( ~~  ) (SomeString s) = "~~ "  + s
let ( ~~~ ) (SomeString s) = "~~~ " + s
let ( ~~~~~~~~~ ) (SomeString s) = "~~~~~~~~~ " + s
let ( ~+  ) (SomeString s) = "~+ "  + s
let ( ~+. ) (SomeString s) = "~+. " + s
let ( ~-  ) (SomeString s) = "~- "  + s
let ( ~-. ) (SomeString s) = "~-. " + s
let ( ~%  ) (SomeString s) = "~% "  + s
let ( ~%% ) (SomeString s) = "~%% " + s
let ( ~&  ) (SomeString s) = "~& "  + s
let ( ~&& ) (SomeString s) = "~&& " + s

let x = SomeString "tilde"

printf "%s\n" (~~  x)           // ~~ tilde
printf "%s\n" (~~~ x)           // ~~~ tilde
printf "%s\n" (~~~~~~~~~ x)     // ~~~~~~~~~ tilde
printf "%s\n" (+  x)            // ~+ tilde      
printf "%s\n" (+. x)            // ~+. tilde
printf "%s\n" (-  x)            // ~- tilde
printf "%s\n" (-. x)            // ~-. tilde
printf "%s\n" (%  x)            // ~% tilde
printf "%s\n" (%% x)            // ~%% tilde
printf "%s\n" (&  x)            // ~& tilde
printf "%s\n" (&& x)            // ~&& tilde

type SomeString = SomeString of string

let ( !! ) (SomeString s) = "!! " + s
let ( !% ) (SomeString s) = "!% " + s 
let ( !& ) (SomeString s) = "!& " + s 
let ( !* ) (SomeString s) = "!* " + s 
let ( !+ ) (SomeString s) = "!+ " + s 
let ( !. ) (SomeString s) = "!. " + s 
let ( !/ ) (SomeString s) = "!/ " + s 
let ( !< ) (SomeString s) = "!< " + s 
let ( !> ) (SomeString s) = "!> " + s
let ( !@ ) (SomeString s) = "!@ " + s 
let ( !^ ) (SomeString s) = "!^ " + s 
let ( !| ) (SomeString s) = "!| " + s 
let ( !~ ) (SomeString s) = "!~ " + s 
let ( !? ) (SomeString s) = "!? " + s 
let ( !@=@> ) (SomeString s) = "@=@> " + s 
let ( !!!/<=>@!!!* ) (SomeString s) = "!!!/<=>@!!!* " + s 
//let ( != )   (SomeString s) = "!= " + s   // prefix != is not allowed
//let ( !=@@ ) (SomeString s) = "!= " + s   // prefix != is not allowed

let y = SomeString "bang"

printf "%s\n" (!! y)            // !! bang
printf "%s\n" (!% y)            // !% bang
printf "%s\n" (!& y)            // !& bang
printf "%s\n" (!* y)            // !* bang     
printf "%s\n" (!+ y)            // !+ bang
printf "%s\n" (!. y)            // !. bang
printf "%s\n" (!/ y)            // !/ bang
printf "%s\n" (!< y)            // !< bang
printf "%s\n" (!> y)            // !> bang
printf "%s\n" (!@ y)            // !@ bang
printf "%s\n" (!^ y)            // !^ bang
printf "%s\n" (!| y)            // !| bang
printf "%s\n" (!~ y)            // !~ bang
printf "%s\n" (!? y)            // !? bang
printf "%s\n" (!@=@> y)         // !@=@> bang
printf "%s\n" (!!!/<=>@!!!* y)  // !!!/<=>@!!!* bang

Joel Mueller 14 年前

没关系,我想我 found the list here ,在第二个表的“重载运算符名称”标题下。