module Language.LBNF.Runtime(
ParseMonad(..)
, err
, printTree
, Doc
, doc
, concatD
, Print(..)
, prPrec
, PrintPlain(..)
) where
import Control.Monad (MonadPlus(..), liftM, foldM, (>=>), ap)
import Control.Applicative ( Applicative(..) )
import Data.Char
data ParseMonad a = Ok a | Bad String
deriving (Read, Show, Eq, Ord)
instance Monad ParseMonad where
return = Ok
fail = Bad
Ok a >>= f = f a
Bad s >>= f = Bad s
instance Functor ParseMonad where
fmap = liftM
instance Applicative ParseMonad where
(<*>) = ap
pure = return
err :: (String -> a) -> ParseMonad a -> a
err e b = case b of
Bad s -> e s
Ok x -> x
printTree :: Print a => a -> String
printTree = render . prt 0
type Doc = [ShowS] -> [ShowS]
doc :: ShowS -> Doc
doc = (:)
render :: Doc -> String
render d = rend 0 (map ($ "") $ d []) "" where
rend i ss = case ss of
"[" :ts -> showChar '[' . rend i ts
"(" :ts -> showChar '(' . rend i ts
"{" :ts -> showChar '{' . new (i+1) . rend (i+1) ts
"}" : ";":ts -> new (i1) . space "}" . showChar ';' . new (i1) . rend (i1) ts
"}" :ts -> new (i1) . showChar '}' . new (i1) . rend (i1) ts
";" :ts -> showChar ';' . new i . rend i ts
t : "," :ts -> showString t . space "," . rend i ts
t : ")" :ts -> showString t . showChar ')' . rend i ts
t : "]" :ts -> showString t . showChar ']' . rend i ts
t :ts -> space t . rend i ts
_ -> id
new i = showChar '\n' . replicateS (2*i) (showChar ' ') . dropWhile isSpace
space t = showString t . (\s -> if null s then "" else (' ':s))
parenth :: Doc -> Doc
parenth ss = doc (showChar '(') . ss . doc (showChar ')')
concatS :: [ShowS] -> ShowS
concatS = foldr (.) id
concatD :: [Doc] -> Doc
concatD = foldr (.) id
replicateS :: Int -> ShowS -> ShowS
replicateS n f = concatS (replicate n f)
class Print a where
prt :: Int -> a -> Doc
prtList :: [a] -> Doc
prtList = concatD . map (prt 0)
instance Print a => Print [a] where
prt _ = prtList
instance Print Char where
prt _ s = doc (showChar '\'' . mkEsc '\'' s . showChar '\'')
prtList s = doc (showChar '"' . concatS (map (mkEsc '"') s) . showChar '"')
mkEsc :: Char -> Char -> ShowS
mkEsc q s = case s of
_ | s == q -> showChar '\\' . showChar s
'\\'-> showString "\\\\"
'\n' -> showString "\\n"
'\t' -> showString "\\t"
_ -> showChar s
prPrec :: Int -> Int -> Doc -> Doc
prPrec i j = if j<i then parenth else id
instance Print Integer where
prt _ x = doc (shows x)
prtList es = case es of
[] -> (concatD [])
[x] -> (concatD [prt 0 x])
x:xs -> (concatD [prt 0 x , doc (showString ",") , prt 0 xs])
instance Print Double where
prt _ x = doc (shows x)
newtype PrintPlain = MkPrintPlain String
instance Print PrintPlain where
prt _ (MkPrintPlain s) = doc $ showString s