datatype/Language/Quote.hs

   1 {-# LANGUAGE TemplateHaskell #-}
   2 {-# LANGUAGE QuasiQuotes #-}
   3 {-# LANGUAGE TupleSections #-}
   4 {-# LANGUAGE ParallelListComp #-}
   5 module Language.Quote (dsl) where
   6
   7 import Data.Char
   8 import Data.Functor.Identity
   9
  10 import Language.Haskell.TH.Syntax
  11 import Language.Haskell.TH.Quote
  12
  13 import Text.Parsec
  14 import Text.Parsec.String
  15 import Text.Parsec.Expr as E
  16 import qualified Text.Parsec.Token as P
  17 import Text.Parsec.Language (haskell)
  18 --
  19 import Language.GenDSL
  20
  21 dsl :: QuasiQuoter
  22 dsl = QuasiQuoter
  23     { quoteExp = \s->location >>= parseExpr s
  24     , quotePat = undefined
  25     , quoteType = undefined
  26     , quoteDec = undefined
  27     }
  28   where
  29     parseExpr :: MonadFail m => String -> Loc -> m Exp
  30     parseExpr s loc =
  31         case runParser p () "" s of
  32           Left err -> fail $ show err
  33           Right e  -> return e
  34       where
  35         file = loc_filename loc
  36         (line, col) = loc_start loc
  37         p = getPosition >>= setPosition . mPos >> expr <* eof
  38         mPos = (flip setSourceName) file .
  39             (flip setSourceLine) line .
  40             (flip setSourceColumn) col
  41
  42 -- Lexer
  43 identifier,operator :: Parser String
  44 identifier = P.identifier haskell
  45 operator = P.operator haskell
  46
  47 parens,braces :: Parser a -> Parser a
  48 braces = P.braces haskell
  49 parens = P.parens haskell
  50
  51 commaSep :: Parser a -> Parser [a]
  52 commaSep = P.commaSep haskell
  53
  54 symbol :: String -> Parser String
  55 symbol = P.symbol haskell
  56
  57 reserved,reservedOp :: String -> Parser ()
  58 reserved = P.reserved haskell
  59 reservedOp = P.reservedOp haskell
  60
  61 -- Parser
  62 pat :: Parser Pat
  63 pat
  64     =   try (RecP <$> con <*> braces (commaSep $ (,) <$> var <* reservedOp "=" <*> pat))
  65     <|> ConP <$> con <*> many pat
  66     <|> try (AsP <$> var <* reservedOp "@" <*> pat)
  67     <|> VarP <$> var
  68     <|> WildP <$ symbol "_"
  69     <|> LitP <$> lit
  70     <|> parens pat
  71
  72 expr :: Parser Exp
  73 expr = buildExpressionParser
  74     [ [bin "^" AssocRight]
  75     , [bin "*" AssocLeft, bin "/" AssocLeft]
  76     , [bin "+" AssocLeft, bin "-" AssocLeft]
  77     , [bin o AssocNone | o <- ["==", "/=", "<", ">", "<=", ">="]]
  78     , [bin "&&" AssocRight]
  79     , [bin "||" AssocRight]
  80     , [E.Infix (fmap ifx $ P.lexeme haskell $ char '`' *> identifier <* char '`') AssocRight]
  81     ] basic
  82   where
  83     bin :: String -> Assoc -> Operator String () Identity Exp
  84     bin str = E.Infix $ ifx (str++".") <$ sat operator (str==)
  85         (("Expected operator " ++ str ++ " but got ")++)
  86
  87     basic :: Parser Exp
  88     basic
  89         =   try (AppE . VarE <$> var <*> (TupE <$> parens (commaSep expr)))
  90         <|> VarE <$> var
  91         <|> mkCase <$ reserved "case" <*> expr <* reserved "of" <*> many1 ((,) <$> pat <* reservedOp "->" <*> expr)
  92         <|> (\i t e->VarE (mkName "if'") `AppE` i `AppE` t `AppE` e) <$ reserved "if" <*> expr <* reserved "then" <*> expr <* reserved "else" <*> expr
  93         <|> parens expr
  94         <|> mkLit . LitE <$> lit
  95         <|> mkLit . ConE . mkName <$> sat identifier ("True"==) ("Expected True but got: "++)
  96         <|> mkLit . ConE . mkName <$> sat identifier ("False"==) ("Expected False but got: "++)
  97
  98 sat :: Parser a -> (a -> Bool) -> (a -> String) -> Parser a
  99 sat p f msg = try (p >>= \a->if f a then pure a else fail (msg a))
 100
 101 lit :: Parser Lit
 102 lit
 103     =   CharL <$> P.charLiteral haskell
 104     <|> IntegerL <$> P.natural haskell
 105
 106 mkLit :: Exp -> Exp
 107 mkLit = AppE $ VarE $ mkName "lit"
 108
 109 con,var :: Parser Name
 110 con = mkName <$> sat identifier (isUpper . head) ("Not a data constructor: "++)
 111 var = mkName <$> sat identifier (isLower . head) ("Not a variable identifier: "++)
 112
 113 -- Convert case to if statements
 114 mkCase :: Exp -> [(Pat, Exp)] -> Exp
 115 mkCase name cases = foldr (uncurry mkCaseMatch) (VarE (mkName "bottom") `AppE` LitE (StringL "Exhausted case")) cases
 116   where
 117     mkCaseMatch :: Pat -> Exp -> Exp -> Exp
 118     mkCaseMatch a e rest = case mkCasePred name a of
 119         [] -> mkCaseLets (mkCaseBinding name a) e
 120         ps -> VarE (mkName "if'") `AppE` foldl1 (ifx "&.") ps `AppE` (mkCaseLets (mkCaseBinding name a) e) `AppE` rest
 121
 122     mkCaseLets :: [Dec] -> Exp -> Exp
 123     mkCaseLets [] e = e
 124     mkCaseLets defs e = LetE defs e
 125
 126     conPtoRecP :: Name -> [Pat] -> Pat
 127     conPtoRecP consName = RecP consName . zip (map (adtFieldName consName) [0..])
 128
 129     mkCasePred :: Exp -> Pat -> [Exp]
 130     mkCasePred e (LitP l) = [ifx "==." (VarE (mkName "lit") `AppE` LitE l) e]
 131     mkCasePred _ (VarP _) = []
 132     mkCasePred e (ConP cons fs) = mkCasePred e $ conPtoRecP cons fs
 133     mkCasePred e (InfixP l cons r) = mkCasePred e (ConP cons [l,r])
 134     mkCasePred e (UInfixP l cons r) = mkCasePred e (ConP cons [l,r])
 135     mkCasePred e (ParensP p) = mkCasePred e p
 136     mkCasePred e (TildeP p) = mkCasePred e p
 137     mkCasePred e (BangP p) = mkCasePred e p
 138     mkCasePred e (AsP _ p) = mkCasePred e p
 139     mkCasePred _  WildP = []
 140     mkCasePred e (RecP cons fs) = VarE (predicateName cons) `AppE` e
 141         : concatMap (\(n, p)->mkCasePred (VarE (selectorName n) `AppE` e) p) fs
 142     mkCasePred _  p = error $ "Unsupported pat: " ++ show p
 143
 144     mkCaseBinding :: Exp -> Pat -> [Dec]
 145     mkCaseBinding _ (LitP _) = []
 146     mkCaseBinding e (VarP v) = [FunD v [Clause [] (NormalB $ e) []]]
 147     mkCaseBinding e (ConP cons fs) = mkCaseBinding e $ conPtoRecP cons fs
 148     mkCaseBinding e (InfixP l cons r) = mkCaseBinding e (ConP cons [l,r])
 149     mkCaseBinding e (UInfixP l cons r) = mkCaseBinding e (ConP cons [l,r])
 150     mkCaseBinding e (ParensP p) = mkCaseBinding e p
 151     mkCaseBinding e (TildeP p) = mkCaseBinding e p
 152     mkCaseBinding e (BangP p) = mkCaseBinding e p
 153     mkCaseBinding e (AsP n p) = FunD n [Clause [] (NormalB $ e) []]:mkCaseBinding e p
 154     mkCaseBinding _  WildP = []
 155     mkCaseBinding e (RecP _ fs) = concatMap (\(n, p)->mkCaseBinding (VarE (selectorName n) `AppE` e) p) fs
 156     mkCaseBinding _  p = error $ "Unsupported pat: " ++ show p