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|
----------------------------------------------------------------------
-- |
-- Module : Parsers
-- Maintainer : Aarne Ranta
-- Stability : Almost Obsolete
-- Portability : Haskell 98
--
-- > CVS $Date: 2005/02/18 19:21:15 $
-- > CVS $Author: peb $
-- > CVS $Revision: 1.4 $
--
-- some parser combinators a la Wadler and Hutton.
-- no longer used in many places in GF
-- (only used in module "EBNF")
-----------------------------------------------------------------------------
module Parsers (-- * Main types and functions
Parser, parseResults, parseResultErr,
-- * Basic combinators (on any token type)
(...), (.>.), (|||), (+||), literal, (***),
succeed, fails, (+..), (..+), (<<<), (|>),
many, some, longestOfMany, longestOfSome,
closure,
-- * Specific combinators (for @Char@ token type)
pJunk, pJ, jL, pTList, pTJList, pElem,
(....), item, satisfy, literals, lits,
pParenth, pCommaList, pOptCommaList,
pArgList, pArgList2,
pIdent, pLetter, pDigit, pLetters,
pAlphanum, pAlphaPlusChar,
pQuotedString, pIntc
) where
import Operations
import Char
infixr 2 |||, +||
infixr 3 ***
infixr 5 .>.
infixr 5 ...
infixr 5 ....
infixr 5 +..
infixr 5 ..+
infixr 6 |>
infixr 3 <<<
type Parser a b = [a] -> [(b,[a])]
parseResults :: Parser a b -> [a] -> [b]
parseResults p s = [x | (x,r) <- p s, null r]
parseResultErr :: Parser a b -> [a] -> Err b
parseResultErr p s = case parseResults p s of
[x] -> return x
[] -> Bad "no parse"
_ -> Bad "ambiguous"
(...) :: Parser a b -> Parser a c -> Parser a (b,c)
(p ... q) s = [((x,y),r) | (x,t) <- p s, (y,r) <- q t]
(.>.) :: Parser a b -> (b -> Parser a c) -> Parser a c
(p .>. f) s = [(c,r) | (x,t) <- p s, (c,r) <- f x t]
(|||) :: Parser a b -> Parser a b -> Parser a b
(p ||| q) s = p s ++ q s
(+||) :: Parser a b -> Parser a b -> Parser a b
p1 +|| p2 = take 1 . (p1 ||| p2)
literal :: (Eq a) => a -> Parser a a
literal x (c:cs) = [(x,cs) | x == c]
literal _ _ = []
(***) :: Parser a b -> (b -> c) -> Parser a c
(p *** f) s = [(f x,r) | (x,r) <- p s]
succeed :: b -> Parser a b
succeed v s = [(v,s)]
fails :: Parser a b
fails s = []
(+..) :: Parser a b -> Parser a c -> Parser a c
p1 +.. p2 = p1 ... p2 *** snd
(..+) :: Parser a b -> Parser a c -> Parser a b
p1 ..+ p2 = p1 ... p2 *** fst
(<<<) :: Parser a b -> c -> Parser a c -- return
p <<< v = p *** (\x -> v)
(|>) :: Parser a b -> (b -> Bool) -> Parser a b
p |> b = p .>. (\x -> if b x then succeed x else fails)
many :: Parser a b -> Parser a [b]
many p = (p ... many p *** uncurry (:)) +|| succeed []
some :: Parser a b -> Parser a [b]
some p = (p ... many p) *** uncurry (:)
longestOfMany :: Parser a b -> Parser a [b]
longestOfMany p = p .>. (\x -> longestOfMany p *** (x:)) +|| succeed []
closure :: (b -> Parser a b) -> (b -> Parser a b)
closure p v = p v .>. closure p ||| succeed v
pJunk :: Parser Char String
pJunk = longestOfMany (satisfy (\x -> elem x "\n\t "))
pJ :: Parser Char a -> Parser Char a
pJ p = pJunk +.. p ..+ pJunk
pTList :: String -> Parser Char a -> Parser Char [a]
pTList t p = p .... many (jL t +.. p) *** (\ (x,y) -> x:y) -- mod. AR 5/1/1999
pTJList :: String -> String -> Parser Char a -> Parser Char [a]
pTJList t1 t2 p = p .... many (literals t1 +.. jL t2 +.. p) *** (uncurry (:))
pElem :: [String] -> Parser Char String
pElem l = foldr (+||) fails (map literals l)
(....) :: Parser Char b -> Parser Char c -> Parser Char (b,c)
p1 .... p2 = p1 ... pJunk +.. p2
item :: Parser a a
item (c:cs) = [(c,cs)]
item [] = []
satisfy :: (a -> Bool) -> Parser a a
satisfy b = item |> b
literals :: (Eq a,Show a) => [a] -> Parser a [a]
literals l = case l of
[] -> succeed []
a:l -> literal a ... literals l *** (\ (x,y) -> x:y)
lits :: (Eq a,Show a) => [a] -> Parser a [a]
lits ts = literals ts
jL :: String -> Parser Char String
jL = pJ . lits
pParenth p = literal '(' +.. pJunk +.. p ..+ pJunk ..+ literal ')'
pCommaList p = pTList "," (pJ p) -- p,...,p
pOptCommaList p = pCommaList p ||| succeed [] -- the same or nothing
pArgList p = pParenth (pCommaList p) ||| succeed [] -- (p,...,p), poss. empty
pArgList2 p = pParenth (p ... jL "," +.. pCommaList p) *** uncurry (:) -- min.2 args
longestOfSome p = (p ... longestOfMany p) *** (\ (x,y) -> x:y)
pIdent = pLetter ... longestOfMany pAlphaPlusChar *** uncurry (:)
where alphaPlusChar c = isAlphaNum c || c=='_' || c=='\''
pLetter = satisfy (`elem` (['A'..'Z'] ++ ['a'..'z'] ++
['À' .. 'Û'] ++ ['à' .. 'û'])) -- no such in Char
pDigit = satisfy isDigit
pLetters = longestOfSome pLetter
pAlphanum = pDigit ||| pLetter
pAlphaPlusChar = pAlphanum ||| satisfy (`elem` "_'")
pQuotedString = literal '"' +.. pEndQuoted where
pEndQuoted =
literal '"' *** (const [])
+|| (literal '\\' +.. item .>. \ c -> pEndQuoted *** (c:))
+|| item .>. \ c -> pEndQuoted *** (c:)
pIntc :: Parser Char Int
pIntc = some (satisfy numb) *** read
where numb x = elem x ['0'..'9']
|
