如何在`StringCvt.scanString（RE.find compiledComment）输入中访问len和pos

Question

背景：我正在尝试使用正则表达式来解析一种语言的注释，该注释以qazxsw poi开头：

//

structure Main =
struct
structure RE = RegExpFn(
    structure P = AwkSyntax
    structure E = ThompsonEngine
)
val regexes = [
    ("[a-zA-z@= ]* *//.*",   fn match => ("comment", match)),
    ("[0-9]*",      fn match => ("2nd", match)),
    ("1tom|2jerry", fn match => ("3rd", match))
]
fun main () =
    let
        val input = "@=abs //sdfasdfdfa sdf as"
        val comment = "[a-zA-z@= ]* *//"
        val compiledComment = RE.compileString comment
    in
        (* #1 StringCvt.scanString (RE.match regexes) input *)
        (* #2 StringCvt.scanString (RE.find compiledComment) input *)
        (* #3 case ... of ... *)
    end

    end

是我的测试用例，我希望只修剪input和prserve //sdfasdfdfa sdf as。

以下是我的一些试验：

• 让@=abs成为StringCvt.scanString (RE.find compiledComment) input的回报值：

---

fun main

---

• 让

  - Main.main();
  [autoloading]
  [autoloading done]
  val it = SOME (Match ({len=8,pos=0},[])) : StringCvt.cs Main.RE.match option

  成为回报值：

---

StringCvt.scanString (RE.match regexes) input

---

这两个案例告诉我

- Main.main();
[autoloading]
[autoloading done]
val it = SOME ("comment",Match ({len=#,pos=#},[]))
  : (string * StringCvt.cs Main.RE.match) option

是我想要的，因为它的值包含StringCvt.scanString (RE.find compiledComment) input，可以用来修剪所有评论。但我对它的价值和类型有点困惑：{len=8,pos=0},[])。我怎样才能访问val it = SOME (Match ({len=8,pos=0},[])) : StringCvt.cs Main.RE.match option和lenhere？为什么pos和StringCvt.cs只能按空间划分？

在使用sml的文档进行搜索后，我将包含以下所有信息：

Main.RE.match

IIUC，

#+BEGIN_SRC sml
StringCvt.scanString (RE.match regexes) input
val it = SOME (
        "comment"  ,           Match             ({len=#,pos=#},[]))
 :      (string    *           StringCvt.cs      Main.RE.match)
         option



StringCvt.scanString (RE.find compiledComment) input
val it = SOME (
        Match                      ({len=8,pos=0},[]))
 :      StringCvt.cs               Main.RE.match
        option



val find : regexp ->
(char,'a) StringCvt.reader -> ({pos : 'a, len : int} option MatchTree.match_tree,'a) StringCvt.reader

val scanString :
((char, cs) reader -> ('a, cs) reader) -> string -> 'a option

val match : (string * ({pos : 'a, len : int} option MatchTree.match_tree -> 'b)) list -> (char,'a) StringCvt.reader -> ('b,'a) StringCvt.reader

#+END_SRC
type cs
The abstract type of the character stream used by scanString. A value of this type represents the state of a character stream. The concrete type is left unspecified to allow implementations a choice of representations. Typically, cs will be an integer index into a string.

的类型应该是Match，StringCvt.cs和({len=8,pos=0},[]))的类型应该是({len=#,pos=#},[]))。然后我开始模式匹配：

Main.RE.match

不幸的，

let
...
in 
case StringCvt.scanString (RE.find compiledComment) input of
            NONE => ""
         |  SOME (
                StringCvt.cs ({len = b, pos = a}, _)) => String.substring (input a b)

似乎我不能使用

main.sml:23.19-23.39 Error: non-constructor applied to argument in pattern
main.sml:23.92 Error: unbound variable or constructor: a
main.sml:23.94 Error: unbound variable or constructor: b
main.sml:23.86-23.95 Error: operator is not a function [tycon mismatch]
  operator: string
  in expression:
    input <errorvar>
[autoloading failed: unable to load module(s)]
stdIn:1.2-1.11 Error: unbound structure: Main in path Main.main

作为模式，因为它不是构造函数。然后我尝试使用StringCvt.cs：

wildcard

,

case StringCvt.scanString (RE.find compiledComment) input of
    NONE => ""
 |  SOME (_ ({len = b, pos = a}, _)) => String.substring (input a b)

那么，main.sml:23.19 Error: non-constructor applied to argument in pattern 的构造函数是必须的吗？我不能再深入挖掘了。你有什么想法？提前致谢

Answer 1

解决了：

Match