forked from GitHub/gf-core
659 lines
20 KiB
Haskell
659 lines
20 KiB
Haskell
----------------------------------------------------------------------
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-- |
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-- Module : Operations
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-- Maintainer : AR
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-- Stability : (stable)
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-- Portability : (portable)
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--
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-- > CVS $Date: 2005/11/11 16:12:41 $
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-- > CVS $Author: bringert $
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-- > CVS $Revision: 1.22 $
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--
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-- some auxiliary GF operations. AR 19\/6\/1998 -- 6\/2\/2001
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--
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-- Copyright (c) Aarne Ranta 1998-2000, under GNU General Public License (see GPL)
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-----------------------------------------------------------------------------
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module GF.Data.Operations (-- * misc functions
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ifNull, onSnd,
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-- * the Error monad
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Err(..), err, maybeErr, testErr, errVal, errIn, derrIn,
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performOps, repeatUntilErr, repeatUntil, okError, isNotError,
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showBad, lookupErr, lookupErrMsg, lookupDefault, updateLookupList,
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mapPairListM, mapPairsM, pairM, mapErr, mapErrN, foldErr,
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(!?), errList, singleton,
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-- ** checking
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checkUnique, titleIfNeeded, errMsg, errAndMsg,
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-- * a three-valued maybe type to express indirections
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Perhaps(..), yes, may, nope,
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mapP,
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unifPerhaps, updatePerhaps, updatePerhapsHard,
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-- * binary search trees; now with FiniteMap
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BinTree, emptyBinTree, isInBinTree, justLookupTree,
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lookupTree, lookupTreeMany, lookupTreeManyAll, updateTree,
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buildTree, filterBinTree,
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sorted2tree, mapTree, mapMTree, tree2list,
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-- * parsing
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WParser, wParseResults, paragraphs,
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-- * printing
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indent, (+++), (++-), (++++), (+++++),
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prUpper, prReplicate, prTList, prQuotedString, prParenth, prCurly,
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prBracket, prArgList, prSemicList, prCurlyList, restoreEscapes,
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numberedParagraphs, prConjList, prIfEmpty, wrapLines,
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-- ** LaTeX code producing functions
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dollar, mbox, ital, boldf, verbat, mkLatexFile,
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begindocument, enddocument,
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-- * extra
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sortByLongest, combinations, mkTextFile, initFilePath,
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-- * topological sorting with test of cyclicity
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topoTest, topoSort, cyclesIn,
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-- * the generic fix point iterator
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iterFix,
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-- * association lists
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updateAssoc, removeAssoc,
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-- * chop into separator-separated parts
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chunks, readIntArg, subSequences,
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-- * state monad with error; from Agda 6\/11\/2001
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STM(..), appSTM, stm, stmr, readSTM, updateSTM, writeSTM, done,
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-- * error monad class
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ErrorMonad(..), checkAgain, checks, allChecks, doUntil
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) where
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import Data.Char (isSpace, toUpper, isSpace, isDigit)
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import Data.List (nub, sortBy, sort, deleteBy, nubBy)
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--import Data.FiniteMap
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import Control.Monad (liftM,liftM2, MonadPlus, mzero, mplus)
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import GF.Data.ErrM
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infixr 5 +++
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infixr 5 ++-
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infixr 5 ++++
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infixr 5 +++++
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infixl 9 !?
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ifNull :: b -> ([a] -> b) -> [a] -> b
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ifNull b f xs = if null xs then b else f xs
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onSnd :: (a -> b) -> (c,a) -> (c,b)
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onSnd f (x, y) = (x, f y)
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-- the Error monad
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-- | analogue of @maybe@
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err :: (String -> b) -> (a -> b) -> Err a -> b
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err d f e = case e of
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Ok a -> f a
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Bad s -> d s
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-- | add msg s to @Maybe@ failures
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maybeErr :: String -> Maybe a -> Err a
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maybeErr s = maybe (Bad s) Ok
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testErr :: Bool -> String -> Err ()
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testErr cond msg = if cond then return () else Bad msg
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errVal :: a -> Err a -> a
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errVal a = err (const a) id
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errIn :: String -> Err a -> Err a
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errIn msg = err (\s -> Bad (s ++++ "OCCURRED IN" ++++ msg)) return
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-- | used for extra error reports when developing GF
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derrIn :: String -> Err a -> Err a
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derrIn m = errIn m -- id
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performOps :: [a -> Err a] -> a -> Err a
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performOps ops a = case ops of
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f:fs -> f a >>= performOps fs
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[] -> return a
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repeatUntilErr :: (a -> Bool) -> (a -> Err a) -> a -> Err a
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repeatUntilErr cond f a = if cond a then return a else f a >>= repeatUntilErr cond f
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repeatUntil :: (a -> Bool) -> (a -> a) -> a -> a
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repeatUntil cond f a = if cond a then a else repeatUntil cond f (f a)
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okError :: Err a -> a
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-- okError = err (error "no result Ok") id
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okError = err (error . ("Bad result occurred" ++++)) id
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isNotError :: Err a -> Bool
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isNotError = err (const False) (const True)
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showBad :: Show a => String -> a -> Err b
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showBad s a = Bad (s +++ show a)
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lookupErr :: (Eq a,Show a) => a -> [(a,b)] -> Err b
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lookupErr a abs = maybeErr ("Unknown" +++ show a) (lookup a abs)
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lookupErrMsg :: (Eq a,Show a) => String -> a -> [(a,b)] -> Err b
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lookupErrMsg m a abs = maybeErr (m +++ "gave unknown" +++ show a) (lookup a abs)
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lookupDefault :: Eq a => b -> a -> [(a,b)] -> b
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lookupDefault d x l = maybe d id $ lookup x l
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updateLookupList :: Eq a => (a,b) -> [(a,b)] -> [(a,b)]
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updateLookupList ab abs = insert ab [] abs where
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insert c cc [] = cc ++ [c]
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insert (a,b) cc ((a',b'):cc') = if a == a'
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then cc ++ [(a,b)] ++ cc'
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else insert (a,b) (cc ++ [(a',b')]) cc'
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mapPairListM :: Monad m => ((a,b) -> m c) -> [(a,b)] -> m [(a,c)]
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mapPairListM f xys = mapM (\ p@(x,_) -> liftM ((,) x) (f p)) xys
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mapPairsM :: Monad m => (b -> m c) -> [(a,b)] -> m [(a,c)]
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mapPairsM f xys = mapM (\ (x,y) -> liftM ((,) x) (f y)) xys
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pairM :: Monad a => (b -> a c) -> (b,b) -> a (c,c)
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pairM op (t1,t2) = liftM2 (,) (op t1) (op t2)
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-- | like @mapM@, but continue instead of halting with 'Err'
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mapErr :: (a -> Err b) -> [a] -> Err ([b], String)
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mapErr f xs = Ok (ys, unlines ss)
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where
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(ys,ss) = ([y | Ok y <- fxs], [s | Bad s <- fxs])
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fxs = map f xs
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-- | alternative variant, peb 9\/6-04
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mapErrN :: Int -> (a -> Err b) -> [a] -> Err ([b], String)
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mapErrN maxN f xs = Ok (ys, unlines (errHdr : ss2))
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where
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(ys, ss) = ([y | Ok y <- fxs], [s | Bad s <- fxs])
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errHdr = show nss ++ " errors occured" ++
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if nss > maxN then ", showing the first " ++ show maxN else ""
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ss2 = map ("* "++) $ take maxN ss
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nss = length ss
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fxs = map f xs
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-- | like @foldM@, but also return the latest value if fails
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foldErr :: (a -> b -> Err a) -> a -> [b] -> Err (a, Maybe String)
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foldErr f s xs = case xs of
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[] -> return (s,Nothing)
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x:xx -> case f s x of
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Ok v -> foldErr f v xx
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Bad m -> return $ (s, Just m)
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-- @!!@ with the error monad
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(!?) :: [a] -> Int -> Err a
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xs !? i = foldr (const . return) (Bad "too few elements in list") $ drop i xs
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errList :: Err [a] -> [a]
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errList = errVal []
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singleton :: a -> [a]
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singleton = (:[])
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-- checking
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checkUnique :: (Show a, Eq a) => [a] -> [String]
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checkUnique ss = ["overloaded" +++ show s | s <- nub overloads] where
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overloads = filter overloaded ss
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overloaded s = length (filter (==s) ss) > 1
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titleIfNeeded :: a -> [a] -> [a]
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titleIfNeeded a [] = []
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titleIfNeeded a as = a:as
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errMsg :: Err a -> [String]
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errMsg (Bad m) = [m]
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errMsg _ = []
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errAndMsg :: Err a -> Err (a,[String])
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errAndMsg (Bad m) = Bad m
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errAndMsg (Ok a) = return (a,[])
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-- | a three-valued maybe type to express indirections
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data Perhaps a b = Yes a | May b | Nope deriving (Show,Read,Eq,Ord)
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yes :: a -> Perhaps a b
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yes = Yes
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may :: b -> Perhaps a b
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may = May
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nope :: Perhaps a b
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nope = Nope
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mapP :: (a -> c) -> Perhaps a b -> Perhaps c b
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mapP f p = case p of
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Yes a -> Yes (f a)
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May b -> May b
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Nope -> Nope
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-- | this is what happens when matching two values in the same module
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unifPerhaps :: (Eq a, Eq b, Show a, Show b) =>
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Perhaps a b -> Perhaps a b -> Err (Perhaps a b)
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unifPerhaps p1 p2 = case (p1,p2) of
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(Nope, _) -> return p2
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(_, Nope) -> return p1
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_ -> if p1==p2 then return p1
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else Bad ("update conflict between" ++++ show p1 ++++ show p2)
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-- | this is what happens when updating a module extension
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updatePerhaps :: (Eq a,Eq b, Show a, Show b) =>
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b -> Perhaps a b -> Perhaps a b -> Err (Perhaps a b)
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updatePerhaps old p1 p2 = case (p1,p2) of
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(Yes a, Nope) -> return $ may old
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(May older,Nope) -> return $ may older
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(_, May a) -> Bad "strange indirection"
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_ -> unifPerhaps p1 p2
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-- | here the value is copied instead of referred to; used for oper types
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updatePerhapsHard :: (Eq a, Eq b, Show a, Show b) => b ->
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Perhaps a b -> Perhaps a b -> Err (Perhaps a b)
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updatePerhapsHard old p1 p2 = case (p1,p2) of
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(Yes a, Nope) -> return $ yes a
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(May older,Nope) -> return $ may older
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(_, May a) -> Bad "strange indirection"
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_ -> unifPerhaps p1 p2
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-- binary search trees
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--- FiniteMap implementation is slower in crucial tests
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data BinTree a b = NT | BT (a,b) !(BinTree a b) !(BinTree a b) deriving (Show)
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-- type BinTree a b = FiniteMap a b
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emptyBinTree :: BinTree a b
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emptyBinTree = NT
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-- emptyBinTree = emptyFM
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isInBinTree :: (Ord a) => a -> BinTree a b -> Bool
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isInBinTree x = err (const False) (const True) . justLookupTree x
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-- isInBinTree = elemFM
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justLookupTree :: (Monad m,Ord a) => a -> BinTree a b -> m b
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justLookupTree = lookupTree (const [])
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lookupTree :: (Monad m,Ord a) => (a -> String) -> a -> BinTree a b -> m b
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lookupTree pr x tree = case tree of
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NT -> fail ("no occurrence of element" +++ pr x)
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BT (a,b) left right
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| x < a -> lookupTree pr x left
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| x > a -> lookupTree pr x right
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| x == a -> return b
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--lookupTree pr x tree = case lookupFM tree x of
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-- Just y -> return y
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-- _ -> fail ("no occurrence of element" +++ pr x)
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lookupTreeMany :: Ord a => (a -> String) -> [BinTree a b] -> a -> Err b
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lookupTreeMany pr (t:ts) x = case lookupTree pr x t of
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Ok v -> return v
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_ -> lookupTreeMany pr ts x
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lookupTreeMany pr [] x = Bad $ "failed to find" +++ pr x
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lookupTreeManyAll :: Ord a => (a -> String) -> [BinTree a b] -> a -> [b]
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lookupTreeManyAll pr (t:ts) x = case lookupTree pr x t of
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Ok v -> v : lookupTreeManyAll pr ts x
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_ -> lookupTreeManyAll pr ts x
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lookupTreeManyAll pr [] x = []
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-- | destructive update
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updateTree :: (Ord a) => (a,b) -> BinTree a b -> BinTree a b
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-- updateTree (a,b) tr = addToFM tr a b
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updateTree = updateTreeGen True
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-- | destructive or not
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updateTreeGen :: (Ord a) => Bool -> (a,b) -> BinTree a b -> BinTree a b
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updateTreeGen destr z@(x,y) tree = case tree of
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NT -> BT z NT NT
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BT c@(a,b) left right
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| x < a -> let left' = updateTree z left in BT c left' right
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| x > a -> let right' = updateTree z right in BT c left right'
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| otherwise -> if destr
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then BT z left right -- removing the old value of a
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else tree -- retaining the old value if one exists
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buildTree :: (Ord a) => [(a,b)] -> BinTree a b
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buildTree = sorted2tree . sortBy fs where
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fs (x,_) (y,_)
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| x < y = LT
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| x > y = GT
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| True = EQ
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-- buildTree = listToFM
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sorted2tree :: Ord a => [(a,b)] -> BinTree a b
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sorted2tree [] = NT
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sorted2tree xs = BT x (sorted2tree t1) (sorted2tree t2) where
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(t1,(x:t2)) = splitAt (length xs `div` 2) xs
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--sorted2tree = listToFM
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--- dm less general than orig
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mapTree :: ((a,b) -> (a,c)) -> BinTree a b -> BinTree a c
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mapTree f NT = NT
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mapTree f (BT a left right) = BT (f a) (mapTree f left) (mapTree f right)
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--mapTree f = mapFM (\k v -> snd (f (k,v)))
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--- fm less efficient than orig?
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mapMTree :: (Ord a,Monad m) => ((a,b) -> m (a,c)) -> BinTree a b -> m (BinTree a c)
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mapMTree f NT = return NT
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mapMTree f (BT a left right) = do
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a' <- f a
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left' <- mapMTree f left
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right' <- mapMTree f right
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return $ BT a' left' right'
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--mapMTree f t = liftM listToFM $ mapM f $ fmToList t
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filterBinTree :: Ord a => (a -> b -> Bool) -> BinTree a b -> BinTree a b
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-- filterFM f t
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filterBinTree f = sorted2tree . filter (uncurry f) . tree2list
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tree2list :: BinTree a b -> [(a,b)] -- inorder
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tree2list NT = []
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tree2list (BT z left right) = tree2list left ++ [z] ++ tree2list right
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--tree2list = fmToList
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-- parsing
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type WParser a b = [a] -> [(b,[a])] -- old Wadler style parser
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wParseResults :: WParser a b -> [a] -> [b]
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wParseResults p aa = [b | (b,[]) <- p aa]
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paragraphs :: String -> [String]
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paragraphs = map unlines . chop . lines where
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chop [] = []
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chop ss = let (ps,rest) = break empty ss in ps : chop (dropWhile empty rest)
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empty = all isSpace
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-- printing
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indent :: Int -> String -> String
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indent i s = replicate i ' ' ++ s
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(+++), (++-), (++++), (+++++) :: String -> String -> String
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a +++ b = a ++ " " ++ b
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a ++- "" = a
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a ++- b = a +++ b
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a ++++ b = a ++ "\n" ++ b
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a +++++ b = a ++ "\n\n" ++ b
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prUpper :: String -> String
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prUpper s = s1 ++ s2' where
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(s1,s2) = span isSpace s
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s2' = case s2 of
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c:t -> toUpper c : t
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_ -> s2
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prReplicate :: Int -> String -> String
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prReplicate n s = concat (replicate n s)
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prTList :: String -> [String] -> String
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prTList t ss = case ss of
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[] -> ""
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[s] -> s
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s:ss -> s ++ t ++ prTList t ss
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prQuotedString :: String -> String
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prQuotedString x = "\"" ++ restoreEscapes x ++ "\""
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prParenth :: String -> String
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prParenth s = if s == "" then "" else "(" ++ s ++ ")"
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prCurly, prBracket :: String -> String
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prCurly s = "{" ++ s ++ "}"
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prBracket s = "[" ++ s ++ "]"
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prArgList, prSemicList, prCurlyList :: [String] -> String
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prArgList = prParenth . prTList ","
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prSemicList = prTList " ; "
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prCurlyList = prCurly . prSemicList
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restoreEscapes :: String -> String
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restoreEscapes s =
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case s of
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[] -> []
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'"' : t -> '\\' : '"' : restoreEscapes t
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'\\': t -> '\\' : '\\' : restoreEscapes t
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c : t -> c : restoreEscapes t
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numberedParagraphs :: [[String]] -> [String]
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numberedParagraphs t = case t of
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[] -> []
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p:[] -> p
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_ -> concat [(show n ++ ".") : s | (n,s) <- zip [1..] t]
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prConjList :: String -> [String] -> String
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prConjList c [] = ""
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prConjList c [s] = s
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prConjList c [s,t] = s +++ c +++ t
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prConjList c (s:tt) = s ++ "," +++ prConjList c tt
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prIfEmpty :: String -> String -> String -> String -> String
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prIfEmpty em _ _ [] = em
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prIfEmpty em nem1 nem2 s = nem1 ++ s ++ nem2
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-- | Thomas Hallgren's wrap lines
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wrapLines :: Int -> String -> String
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wrapLines n "" = ""
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wrapLines n s@(c:cs) =
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if isSpace c
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then c:wrapLines (n+1) cs
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else case lex s of
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[(w,rest)] -> if n'>=76
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then '\n':w++wrapLines l rest
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else w++wrapLines n' rest
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where n' = n+l
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l = length w
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_ -> s -- give up!!
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--- optWrapLines = if argFlag "wraplines" True then wrapLines 0 else id
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-- LaTeX code producing functions
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dollar, mbox, ital, boldf, verbat :: String -> String
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dollar s = '$' : s ++ "$"
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mbox s = "\\mbox{" ++ s ++ "}"
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ital s = "{\\em" +++ s ++ "}"
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boldf s = "{\\bf" +++ s ++ "}"
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verbat s = "\\verbat!" ++ s ++ "!"
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mkLatexFile :: String -> String
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mkLatexFile s = begindocument +++++ s +++++ enddocument
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begindocument, enddocument :: String
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begindocument =
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"\\documentclass[a4paper,11pt]{article}" ++++ -- M.F. 25/01-02
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"\\setlength{\\parskip}{2mm}" ++++
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"\\setlength{\\parindent}{0mm}" ++++
|
|
"\\setlength{\\oddsidemargin}{0mm}" ++++
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|
("\\setlength{\\evensidemargin}{"++"-2mm}") ++++ -- peb 27/5-04: to prevent hugs-mode
|
|
("\\setlength{\\topmargin}{"++"-8mm}") ++++ -- from treating the rest as comments
|
|
"\\setlength{\\textheight}{240mm}" ++++
|
|
"\\setlength{\\textwidth}{158mm}" ++++
|
|
"\\begin{document}\n"
|
|
enddocument =
|
|
"\n\\end{document}\n"
|
|
|
|
|
|
sortByLongest :: [[a]] -> [[a]]
|
|
sortByLongest = sortBy longer where
|
|
longer x y
|
|
| x' > y' = LT
|
|
| x' < y' = GT
|
|
| True = EQ
|
|
where
|
|
x' = length x
|
|
y' = length y
|
|
|
|
-- | 'combinations' is the same as @sequence@!!!
|
|
-- peb 30\/5-04
|
|
combinations :: [[a]] -> [[a]]
|
|
combinations t = case t of
|
|
[] -> [[]]
|
|
aa:uu -> [a:u | a <- aa, u <- combinations uu]
|
|
|
|
|
|
mkTextFile :: String -> IO ()
|
|
mkTextFile name = do
|
|
s <- readFile name
|
|
let s' = prelude name ++ "\n\n" ++ heading name ++ "\n" ++ object s
|
|
writeFile (name ++ ".hs") s'
|
|
where
|
|
prelude name = "module " ++ name ++ " where"
|
|
heading name = "txt" ++ name ++ " ="
|
|
object s = mk s ++ " \"\""
|
|
mk s = unlines [" \"" ++ escs line ++ "\" ++ \"\\n\" ++" | line <- lines s]
|
|
escs s = case s of
|
|
c:cs | elem c "\"\\" -> '\\' : c : escs cs
|
|
c:cs -> c : escs cs
|
|
_ -> s
|
|
|
|
initFilePath :: FilePath -> FilePath
|
|
initFilePath f = reverse (dropWhile (/='/') (reverse f))
|
|
|
|
-- | topological sorting with test of cyclicity
|
|
topoTest :: Eq a => [(a,[a])] -> Either [a] [[a]]
|
|
topoTest g = if length g' == length g then Left g' else Right (cyclesIn g ++[[]])
|
|
where
|
|
g' = topoSort g
|
|
|
|
cyclesIn :: Eq a => [(a,[a])] -> [[a]]
|
|
cyclesIn deps = nubb $ clean $ filt $ iterFix findDep immediate where
|
|
immediate = [[y,x] | (x,xs) <- deps, y <- xs]
|
|
findDep chains = [y:x:chain |
|
|
x:chain <- chains, (x',xs) <- deps, x' == x, y <- xs,
|
|
notElem y (init chain)]
|
|
|
|
clean = map remdup
|
|
nubb = nubBy (\x y -> y == reverse x)
|
|
filt = filter (\xs -> last xs == head xs)
|
|
remdup (x:xs) = x : remdup xs' where xs' = dropWhile (==x) xs
|
|
remdup [] = []
|
|
|
|
|
|
-- | topological sorting
|
|
topoSort :: Eq a => [(a,[a])] -> [a]
|
|
topoSort g = reverse $ tsort 0 [ffs | ffs@(f,_) <- g, inDeg f == 0] [] where
|
|
tsort _ [] r = r
|
|
tsort k (ffs@(f,fs) : cs) r
|
|
| elem f r = tsort k cs r
|
|
| k > lx = r
|
|
| otherwise = tsort (k+1) cs (f : tsort (k+1) (info fs) r)
|
|
info hs = [(f,fs) | (f,fs) <- g, elem f hs]
|
|
inDeg f = length [t | (h,hs) <- g, t <- hs, t == f]
|
|
lx = length g
|
|
|
|
-- | the generic fix point iterator
|
|
iterFix :: Eq a => ([a] -> [a]) -> [a] -> [a]
|
|
iterFix more start = iter start start
|
|
where
|
|
iter old new = if (null new')
|
|
then old
|
|
else iter (new' ++ old) new'
|
|
where
|
|
new' = filter (`notElem` old) (more new)
|
|
|
|
-- association lists
|
|
|
|
updateAssoc :: Eq a => (a,b) -> [(a,b)] -> [(a,b)]
|
|
updateAssoc ab@(a,b) as = case as of
|
|
(x,y): xs | x == a -> (a,b):xs
|
|
xy : xs -> xy : updateAssoc ab xs
|
|
[] -> [ab]
|
|
|
|
removeAssoc :: Eq a => a -> [(a,b)] -> [(a,b)]
|
|
removeAssoc a = filter ((/=a) . fst)
|
|
|
|
-- | chop into separator-separated parts
|
|
chunks :: Eq a => a -> [a] -> [[a]]
|
|
chunks sep ws = case span (/= sep) ws of
|
|
(a,_:b) -> a : bs where bs = chunks sep b
|
|
(a, []) -> if null a then [] else [a]
|
|
|
|
readIntArg :: String -> Int
|
|
readIntArg n = if (not (null n) && all isDigit n) then read n else 0
|
|
|
|
|
|
-- state monad with error; from Agda 6/11/2001
|
|
|
|
newtype STM s a = STM (s -> Err (a,s))
|
|
|
|
appSTM :: STM s a -> s -> Err (a,s)
|
|
appSTM (STM f) s = f s
|
|
|
|
stm :: (s -> Err (a,s)) -> STM s a
|
|
stm = STM
|
|
|
|
stmr :: (s -> (a,s)) -> STM s a
|
|
stmr f = stm (\s -> return (f s))
|
|
|
|
instance Monad (STM s) where
|
|
return a = STM (\s -> return (a,s))
|
|
STM c >>= f = STM (\s -> do
|
|
(x,s') <- c s
|
|
let STM f' = f x
|
|
f' s')
|
|
|
|
readSTM :: STM s s
|
|
readSTM = stmr (\s -> (s,s))
|
|
|
|
updateSTM :: (s -> s) -> STM s ()
|
|
updateSTM f = stmr (\s -> ((),f s))
|
|
|
|
writeSTM :: s -> STM s ()
|
|
writeSTM s = stmr (const ((),s))
|
|
|
|
done :: Monad m => m ()
|
|
done = return ()
|
|
|
|
class Monad m => ErrorMonad m where
|
|
raise :: String -> m a
|
|
handle :: m a -> (String -> m a) -> m a
|
|
handle_ :: m a -> m a -> m a
|
|
handle_ a b = a `handle` (\_ -> b)
|
|
|
|
instance ErrorMonad Err where
|
|
raise = Bad
|
|
handle a@(Ok _) _ = a
|
|
handle (Bad i) f = f i
|
|
|
|
instance ErrorMonad (STM s) where
|
|
raise msg = STM (\s -> raise msg)
|
|
handle (STM f) g = STM (\s -> (f s)
|
|
`handle` (\e -> let STM g' = (g e) in
|
|
g' s))
|
|
|
|
-- | if the first check fails try another one
|
|
checkAgain :: ErrorMonad m => m a -> m a -> m a
|
|
checkAgain c1 c2 = handle_ c1 c2
|
|
|
|
checks :: ErrorMonad m => [m a] -> m a
|
|
checks [] = raise "no chance to pass"
|
|
checks cs = foldr1 checkAgain cs
|
|
|
|
allChecks :: ErrorMonad m => [m a] -> m [a]
|
|
allChecks ms = case ms of
|
|
(m: ms) -> let rs = allChecks ms in handle_ (liftM2 (:) m rs) rs
|
|
_ -> return []
|
|
|
|
doUntil :: ErrorMonad m => (a -> Bool) -> [m a] -> m a
|
|
doUntil cond ms = case ms of
|
|
a:as -> do
|
|
v <- a
|
|
if cond v then return v else doUntil cond as
|
|
_ -> raise "no result"
|
|
|
|
-- subsequences sorted from longest to shortest ; their number is 2^n
|
|
subSequences :: [a] -> [[a]]
|
|
subSequences = sortBy (\x y -> compare (length y) (length x)) . subs where
|
|
subs xs = case xs of
|
|
[] -> [[]]
|
|
x:xs -> let xss = subs xs in [x:y | y <- xss] ++ xss
|