程序代写 - Do not modify anything in this file!

— Do not modify anything in this file!
module Definitions where

type ErrMsg = String — human-readable error messages

type EM = Either ErrMsg — can be used directly as a Monad

type EGrammar = [ERule]
type ERule = (RLHS, ERHS)

type RLHS = (NTName, RKind, Maybe Type)
type NTName = String

data RKind = RPlain | RToken | RSep
deriving (Eq,Show,Read)

data Action =
AUser HText
| AVar String
| A Action
| AApp Action Action
| ACst String
deriving (Eq,Show,Read)

type HText = String — Haskell text from user
type Type = Action

type Grammar = [Rule]
type Rule = (RLHS, [([Simple]{-seq-}, Action)]{-alts-})
module Generator (render, prelude) where

import Definitions
import Data.Char (isUpper)
import Data.List (intercalate)

gp p = “p_” ++ p — added in front of all generated parsers
rp f = “RP.” ++ f — added in front of all ReadP functions

renderH :: HText -> String
renderH h = “{-U-}(” ++ h ++ “)” — explicitly tag user-supplied code

renderA :: Action -> String
renderA (AUser h) = renderH h
renderA (ACst s) = s
renderA (AVar x) = x
renderA (ALam x a) = “(\\” ++ x ++ ” -> ” ++ renderA a ++ “)”
renderA (AApp a1 a2) = “(” ++ renderA a1 ++ ” ” ++ renderA a2 ++ “)”

renderS :: Simple -> String
renderS (SLit s) =
“do {” ++ rp “string” ++ ” ” ++ show s ++ “; ” ++ gp “_” ++ ” ” ++ show s ++”}”
renderS (SNTerm s) = gp s
renderS SAnyChar = rp “get”
renderS (SChar c) = rp “char” ++ ” ” ++ show c
renderS (SNot s) = “nfb_ (” ++ renderS s ++ “)”
renderS (SPred s h) = “pred_ ” ++ renderS s ++ ” ” ++ renderH h
renderS SDummy = “return (error \”dummy\”)”

renderR :: Rule -> String
renderR ((nt,rk,mt), alts) =
let rbind p i = “_” ++ show i ++ ” <- " ++ renderS p rseq (ps, r) = "do {" ++ intercalate "; " (zipWith rbind ps [1..]) ++ "; return_ " ++ renderA r ++ "}" rhs = case map rseq alts of ss -> rp “choice” ++ ” [” ++ intercalate “, ” ss ++ “]”
exp = case rk of
RPlain -> rhs
RToken -> “do r <- " ++ rhs ++ "; " ++ gp "_" ++ " \"\"; return r" RSep -> “\\_0 -> ” ++ rhs
pn = gp nt
sig = case mt of
Nothing -> “”
Just tp -> pn ++ ” :: Parser_ ” ++ renderA tp ++ “\n”
in sig ++ pn ++ ” = ” ++ exp

render :: Grammar -> String
render rs = intercalate “\n” (map renderR rs)

“type Parser_ a = ” ++ rp “ReadP” ++ ” a\n” ++
“return_ :: a -> Parser_ a — sometimes req’d for overloading resolution\n” ++
“return_ = return\n” ++
“nfb_ :: Parser_ a -> Parser_ () — notFollowedBy\n” ++
“nfb_ p = do b <- (p >> return True) ” ++ rp “<++" ++ " return False\n" ++ " if b then " ++ rp "pfail" ++ " else return ()\n" ++ "pred_ :: Parser_ a -> (a -> Bool) -> Parser_ a\n”++
“pred_ p f = do a <- p; if f a then return a else " ++ rp "pfail" ++ "\n" ++ "parseTop p s = case " ++ rp "readP_to_S" ++ " (do " ++ gp "_" ++ " \"\"; a <- p; " ++ rp "eof" ++ "; return a) s of\n"++ " [] -> Left \”no parse\”\n”++
” [(a,_)] -> Right a\n”++
” _ -> Left \”ambiguous\”\n\n”
— This is a wrapper module. Do not modify it
module Parser (parseSpec) where

import ParserImpl
— Put yor parser implementation in this file
module ParserImpl where

import Definitions
— import ReadP or Parsec

parseSpec :: String -> EM (String, EGrammar)
parseSpec = undefined
— This is a wrapper module. Do not modify it
module Transformer (convert, lre, lfactor) where

import TransformerImpl
— Put yor transformer implementation in this file
module TransformerImpl where

import Definitions

convert :: EGrammar -> EM Grammar
convert = undefined

lre :: Grammar -> EM Grammar
lre = undefined

lfactor :: Grammar -> EM Grammar
lfactor = undefined

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