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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% %
% Frown --- An LALR(k) parser generator for Haskell 98 %
% Copyright (C) 2001-2005 Ralf Hinze %
% %
% This program is free software; you can redistribute it and/or modify %
% it under the terms of the GNU General Public License (version 2) as %
% published by the Free Software Foundation. %
% %
% This program is distributed in the hope that it will be useful, %
% but WITHOUT ANY WARRANTY; without even the implied warranty of %
% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the %
% GNU General Public License for more details. %
% %
% You should have received a copy of the GNU General Public License %
% along with this program; see the file COPYING. If not, write to %
% the Free Software Foundation, Inc., 59 Temple Place - Suite 330, %
% Boston, MA 02111-1307, USA. %
% %
% Contact information %
% Email: Ralf Hinze <ralf@cs.uni-bonn.de> %
% Homepage: http://www.informatik.uni-bonn.de/~ralf/ %
% Paper mail: Dr. Ralf Hinze %
% Institut für Informatik III %
% Universität Bonn %
% Römerstraße 164 %
% 53117 Bonn, Germany %
% %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%-------------------------------------------------------------------------------
\section{Auxiliary definitions}
%-------------------------------------------------------------------------------
> module Base ( module Base )
> where
>
> import Prettier
> import Control.Applicative
> import Control.Monad ( MonadPlus(..) )
> import System.IO
> import System.Exit
%-------------------------------------------------------------------------------
\subsection{List utilities}
%-------------------------------------------------------------------------------
%{
%format a_(b) = "{" a "}_{" b "}"
> type List a = [a]
> equal :: (Eq a) => [a] -> Bool
> equal [] = True
> equal [_a] = True
> equal (a1 : as@(a2 : _)) = a1 == a2 && equal as
The call |breakAfter p [a_(1), ldots, a_(n)]| yields |([a_(1), ldots,
a_(i)], [a_(i+1), ldots , a_(n)])| such that |p (a_(i)) = True| and
|p (a_(j)) = False| for |j < i|.
> breakAfter :: (a -> Bool) -> [a] -> ([a], [a])
> breakAfter _p [] = ([], [])
> breakAfter p (a : as)
> | p a = ([a], as)
> | otherwise = a <| breakAfter p as
> breaks :: ([a] -> Bool) -> [a] -> ([a], [a])
> breaks _p [] = ([], [])
> breaks p as@(a : as')
> | p as = ([], as)
> | otherwise = a <| breaks p as'
> isPrefix :: (Eq a) => [a] -> [a] -> Bool
> p `isPrefix` as = p == take (length p) as
> {-
> intersperse :: a -> [a] -> [a]
> intersperse _s [] = []
> intersperse s (a : x) = a : intersperse1 x
> where intersperse1 [] = []
> intersperse1 (b : y)= s : b : intersperse1 y
> -}
Required?
> groupBy :: (a -> a -> Bool) -> [a] -> [[a]]
> groupBy _p [] = []
> groupBy _p [a] = [[a]]
> groupBy p (a:b:x) | p a b = tack a (groupBy p (b:x))
> | otherwise = [a] : groupBy p (b:x)
> infixr 5 <| -- same fixity as `|:|'
> (<|) :: a -> ([a], b) -> ([a], b)
> a <| (as, b) = (a : as, b)
> tack :: a -> [[a]] -> [[a]]
> tack a xs = (a : head xs) : tail xs
%}
%-------------------------------------------------------------------------------
\subsection{Monad utilities}
%-------------------------------------------------------------------------------
> panic :: String -> IO a
> panic s = do hPutStrLn stderr ("*** panic: " ++ s)
> exitFailure
> warning :: String -> IO ()
> warning s = hPutStrLn stderr ("* warning: " ++ s)
>
> impossible :: String -> a
> impossible name = error ("The `impossible' happened in \"" ++ name ++ "\".\n"
> ++ "Please, report this as a bug to\n"
> ++ "Ralf Hinze (ralf@cs.uni-bonn.de).")
A simple exception monad.
> data Result a = Fail String | Return a
> instance Functor Result where
> f `fmap` Return x = Return (f x)
> f `fmap` Fail xs = Fail xs
> instance Applicative Result where
> pure = Return
> Return f <*> Return x = Return (f x)
> Fail xs <*> Fail ys = Fail (xs ++ ys)
> instance Alternative Result where
> empty = fail ""
> Fail _ <|> m = m
> m@(Return _) <|> _ = m
> instance Monad Result where
> Fail s >>= _k = Fail s
> Return a >>= k = k a
> return = Return
> fail = Fail
> instance MonadPlus Result where
> mzero = fail ""
> Fail _s `mplus` m = m
> Return a `mplus` _m = Return a
%-------------------------------------------------------------------------------
\subsection{Reverse or snoc lists}
%-------------------------------------------------------------------------------
> infixl 5 :>
> data RevList a = Nil | RevList a :> a
> deriving (Show, Eq, Ord)
>
> instance (Pretty a) => Pretty (RevList a) where
> prettyPrec _ as = prettyList (list as)
>
> instance Functor RevList where
> fmap _f Nil = Nil
> fmap f (x :> a) = fmap f x :> f a
>
> list :: RevList a -> List a
> list x = shunt x []
>
> revList :: List a -> RevList a
> revList x = revShunt Nil x
> shunt :: RevList a -> List a -> List a
> shunt Nil r = r
> shunt (l :> a) r = shunt l (a : r)
>
> revShunt :: RevList a -> List a -> RevList a
> revShunt l [] = l
> revShunt l (a : r) = revShunt (l :> a) r
>
> revLength :: RevList a -> Int
> revLength Nil = 0
> revLength (x :> _a) = revLength x + 1
>
> isSuffix :: (Eq a) => RevList a -> RevList a -> Bool
> Nil `isSuffix` _y = True
> (_x :> _a) `isSuffix` Nil = False
> (x :> a) `isSuffix` (y :> b) = a == b && x `isSuffix` y
> revTake :: Int -> RevList a -> RevList a
> revTake 0 _ = Nil
> revTake _ Nil = Nil
> revTake n (as :> a) = revTake (n - 1) as :> a
> revDrop :: Int -> RevList a -> RevList a
> revDrop 0 as = as
> revDrop _ Nil = Nil
> revDrop n (as :> _a) = revDrop (n - 1) as
%-------------------------------------------------------------------------------
\subsection{Formatting text}
%-------------------------------------------------------------------------------
> spaces :: Int -> [Char]
> spaces n = replicate n ' '
> cjustifyWith :: a -> Int -> [a] -> [a]
> cjustifyWith c n s = replicate l c ++ s ++ replicate r c
> where m = n - length s
> l = m `div` 2
> r = m - l
> cjustify :: Int -> String -> String
> cjustify = cjustifyWith ' '
> ljustify :: Int -> String -> String
> ljustify n s = s ++ spaces (n - length s)
> rjustify :: Int -> String -> String
> rjustify n s = spaces (n - length s) ++ s
%-------------------------------------------------------------------------------
\subsection{Miscellaneous}
%-------------------------------------------------------------------------------
> applyWithDefault :: (a -> Maybe b) -> b -> a -> b
> applyWithDefault f def a = case f a of { Nothing -> def; Just v -> v }
> applyWithContinuation :: (a -> Maybe b) -> (b -> c) -> c -> a -> c
> applyWithContinuation f succ err a
> = case f a of { Nothing -> err; Just v -> succ v }
> equ1 :: (Eq a) => (a, b) -> (a, b) -> Bool
> equ1 (a, _) (a', _) = a == a'
>
> leq1 :: (Ord a) => (a, b) -> (a, b) -> Bool
> leq1 (a, _) (a', _) = a <= a'
> equ2 :: (Eq b) => (a, b) -> (a, b) -> Bool
> equ2 (_, b) (_, b') = b == b'
>
> leq2 :: (Ord b) => (a, b) -> (a, b) -> Bool
> leq2 (_, b) (_, b') = b <= b'
> leqLength :: [a] -> [a] -> Bool
> leqLength x y = length x >= length y
|
