[英]translate Haskell (monadic) to F#
幫我翻譯以下Haskell代碼塊。 run函數產生文本字符串,該字符串對應於抽象為Pattern的給定正則表達式。 您可以在下面的F#代碼塊中看到Pattern類型的聲明。 您可以測試運行功能,例如
genex $ POr [PConcat [PEscape( DoPa 1) 'd'], PConcat [PEscape (DoPa 2) 'd']]
{-# LANGUAGE RecordWildCards, NamedFieldPuns #-}
import qualified Data.Text as T
import qualified Control.Monad.Stream as Stream
import Text.Regex.TDFA.Pattern
import Control.Monad.State
import Control.Applicative
genex = Stream.toList . run
maxRepeat :: Int
maxRepeat = 3
each = foldl1 (<|>) . map return
run :: Pattern -> Stream.Stream T.Text
run p = case p of
PBound low high p -> do
n <- each [low..maybe (low+maxRepeat) id high]
fmap T.concat . sequence $ replicate n (run p)
PConcat ps -> fmap T.concat . Stream.suspended . sequence $ map run ps
POr xs -> foldl1 mplus $ map run xs
PEscape {..} -> case getPatternChar of
'd' -> chars $ ['0'..'9']
'w' -> chars $ ['0'..'9'] ++ '_' : ['a'..'z'] ++ ['A'..'Z']
ch -> isChar ch
_ -> error $ show p
where
isChar = return . T.singleton
chars = each . map T.singleton
下面,我嘗試一下。 它有效,但不正確。 問題出在下面。 假設解析產生這樣的Pattern
解析“ \\\\ d \\\\ d” ;; 值:模式= POr [PConcat [PEscape(DoPa 1,'d'); PEscape(DoPa 2,'d')]]
和
解析“ \\\\ d {2}” ;; 值:模式= POr [PConcat [PBound(2,Some 2,PEscape(DoPa 1,'d'))]]
因此,這兩種模式都可以運行,我希望收到seq [['2'; '2']; [ '2'; '3']; [ '2'; '1']; [ '2'; '4']; ...]對應於seq [“ 22”; “23”; “21”; “24”; ...] (每個字符串2個符號)
這在第一種情況下有效,
POr [PConcat [PEscape(DoPa 1,'d'); PEscape(DoPa 2,'d')]] |>運行;; val it:seq = seq [['2'; '2']; [ '2'; '3']; [ '2'; '1']; [ '2'; '4']; ...]
seq [“ 22”; “23”; “21”; “24”; ...]
但不是第二
POr [PConcat [PBound(2,Some 2,PEscape(DoPa 1,'d'))]] |>運行;; val it:seq = seq [['2']; [ '2']; [ '2']; [ '3']; ...]
seq [“ 2”; “ 2”,“ 2”; “ 3”,“ 2”; “ 1”,“ 2”; “ 4”; ...] (每個字符串1個符號)
我使用以下條款測試了不同的變體:
| POr ps -> Seq.concat (List.map run ps)
| PConcat ps -> (sequence (List.map (run >> Seq.concat) ps))
| PBound (low,high,p) ->
但都是徒勞的。 我不知道有效的翻譯。
-也許我應該使用String或Array而不是char列表。
-我認為Seq非常類似於Control.Monad.Stream。 這樣對嗎?
預先感謝您的幫助
open System
/// Used to track elements of the pattern that accept characters or are anchors
type DoPa = DoPa of int
/// Pattern is the type returned by the regular expression parser.
/// This is consumed by the CorePattern module and the tender leaves
/// are nibbled by the TNFA module.
type Pattern = PEmpty
| POr of Pattern list // flattened by starTrans
| PConcat of Pattern list // flattened by starTrans
| PBound of int * (int option) * Pattern // eliminated by starTrans
| PEscape of DoPa * char // Backslashed Character
let maxRepeat = 3
let maybe deflt f opt =
match opt with
| None -> deflt
| Some v -> f v
/// Cartesian production
/// try in F# interactive: sequence [[1;2];[3;4]];;
let rec sequence = function
| [] -> Seq.singleton []
| (l::ls) -> seq { for x in l do for xs in sequence ls do yield (x::xs) }
let from'space'to'tilda = [' '..'~'] |> List.ofSeq
let numbers = ['0'..'9'] |> List.ofSeq
let numbers'and'alphas = (['0'..'9'] @ '_' :: ['a'..'z'] @ ['A'..'Z']) |> List.ofSeq
let whites = ['\009'; '\010'; '\012'; '\013'; '\032' ] |> List.ofSeq
let rec run (p:Pattern) : seq<char list> =
let chars chs = seq { yield [for s in chs -> s] }
match p with
| POr ps -> Seq.concat (List.map run ps)
| PConcat ps -> (sequence (List.map (run >> Seq.concat) ps))
| PBound (low,high,p) ->
let ns = seq {low .. maybe (low + maxRepeat) id high}
Seq.concat (seq { for n in ns do yield sequence (List.replicate n (((run >> Seq.concat) p))) })
// Seq.concat (seq { for n in ns do yield ((List.replicate n (run p)) |> Seq.concat |> List.ofSeq |> sequence)})
//((List.replicate low (run p)) |> Seq.concat |> List.ofSeq |> sequence)
// PConcat [ for n in ns -> p] |> run
| PEscape(_, ch) ->
match ch with
| 'd' -> chars numbers
| 'w' -> chars numbers'and'alphas
| ch -> chars [ch]
| _ -> Seq.empty
我不知道為什么不將Haskell的Data.Text
轉換為F#中的string
,您只需要模仿兩個函數即可。 除此之外,我僅作了一些更改以使其工作,這樣您就可以輕松地將其與原始代碼進行比較,請參閱(* *)之間的替換代碼
open System
// Mimic Data.Text as T
module T =
let concat (x:seq<_>) = System.String.Concat x
let singleton (x:char) = string x
/// Used to track elements of the pattern that accept characters or are anchors
type DoPa = DoPa of int
/// Pattern is the type returned by the regular expression parser.
/// This is consumed by the CorePattern module and the tender leaves
/// are nibbled by the TNFA module.
type Pattern = PEmpty
| POr of Pattern list // flattened by starTrans
| PConcat of Pattern list // flattened by starTrans
| PBound of int * (int option) * Pattern // eliminated by starTrans
| PEscape of DoPa * char // Backslashed Character
let maxRepeat = 3
let maybe deflt f opt =
match opt with
| None -> deflt
| Some v -> f v
/// Cartesian production
/// try in F# interactive: sequence [[1;2];[3;4]];;
let rec sequence = function
| [] -> Seq.singleton []
| (l::ls) -> seq { for x in l do for xs in sequence ls do yield (x::xs) }
let from'space'to'tilda = [' '..'~'] |> List.ofSeq
let numbers = ['0'..'9'] |> List.ofSeq
let numbers'and'alphas = (['0'..'9'] @ '_' :: ['a'..'z'] @ ['A'..'Z']) |> List.ofSeq
let whites = ['\009'; '\010'; '\012'; '\013'; '\032' ] |> List.ofSeq
let rec run (p:Pattern) (*: seq<char list> *) =
(* let chars chs = seq { yield [for s in chs -> s] } *)
let chars (chs:seq<char>) = Seq.map string chs
match p with
| POr ps -> Seq.concat (List.map run ps)
| PConcat ps -> Seq.map T.concat << sequence <| List.map run ps (* (sequence (List.map (run >> Seq.concat) ps)) *)
| PBound (low,high,p) ->
seq {
for n in [low..maybe (low+maxRepeat) id high] do
yield! ( (Seq.map T.concat << sequence) (List.replicate n (run p)) )}
(*let ns = seq {low .. maybe (low + maxRepeat) id high}
Seq.concat (seq { for n in ns do yield sequence (List.replicate n (((run >> Seq.concat) p))) *)
// Seq.concat (seq { for n in ns do yield ((List.replicate n (run p)) |> Seq.concat |> List.ofSeq |> sequence)})
//((List.replicate low (run p)) |> Seq.concat |> List.ofSeq |> sequence)
// PConcat [ for n in ns -> p] |> run
| PEscape(_, ch) ->
match ch with
| 'd' -> chars numbers
| 'w' -> chars numbers'and'alphas
| ch -> chars [ch]
| _ -> Seq.empty
UPDATE
如果要將Haskell代碼轉換為F#,則可以嘗試使用模仿許多Haskell函數(包括使用類型類的那些函數)的代碼 。 我做了一個盡可能接近原始Haskell代碼的測試,但是使用F#List(不是惰性的),它看起來像這樣:
#load "Prelude.fs"
#load "Monad.fs"
#load "Applicative.fs"
#load "Monoid.fs"
open Prelude
open Control.Monad.Base
open Control.Applicative
module T =
let concat (x:list<_>) = System.String.Concat x
let singleton (x:char) = string x
type DoPa = DoPa of int
type Pattern = PEmpty
| POr of Pattern list
| PConcat of Pattern list
| PBound of int * (int option) * Pattern
| PEscape of DoPa * char
let maxRepeat = 3
let inline each x = foldl1 (<|>) << map return' <| x
let rec run p:list<_> =
let inline isChar x = return' << T.singleton <| x
let inline chars x = each << map T.singleton <| x
match p with
| PBound (low,high,p) -> do' {
let! n = each [low..maybe (low+maxRepeat) id high]
return! (fmap T.concat << sequence <| replicate n (run p))}
| PConcat ps -> fmap T.concat << sequence <| map run ps
| POr xs -> foldl1 mplus <| map run xs
| PEscape (_, ch) ->
match ch with
| 'd' -> chars <| ['0'..'9']
| 'w' -> chars <| ['0'..'9'] @ '_' :: ['a'..'z'] @ ['A'..'Z']
| ch -> isChar ch
| _ -> failwith <| string p
let genex = run
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