%
+% (c) The University of Glasgow 2006
% (c) The University of Glasgow 1992-2002
%
\section[Util]{Highly random utility functions}
zipLazy, stretchZipWith,
mapFst, mapSnd,
mapAndUnzip, mapAndUnzip3,
- nOfThem, filterOut,
+ nOfThem, filterOut, partitionWith, splitEithers,
lengthExceeds, lengthIs, lengthAtLeast,
listLengthCmp, atLength, equalLength, compareLength,
transitiveClosure,
-- accumulating
- mapAccumL, mapAccumR, mapAccumB,
foldl2, count, all2,
takeList, dropList, splitAtList, split,
-- comparisons
isEqual, eqListBy,
- thenCmp, cmpList, prefixMatch, suffixMatch, maybePrefixMatch,
+ thenCmp, cmpList, maybePrefixMatch,
removeSpaces,
-- strictness
- foldl', seqList,
+ seqList,
-- pairs
unzipWith,
import Panic ( panic, trace )
import FastTypes
-import EXCEPTION ( Exception(..), finally, throwDyn, catchDyn, throw )
-import qualified EXCEPTION as Exception
-import DYNAMIC ( Typeable )
-import DATA_IOREF ( IORef, newIORef )
-import UNSAFE_IO ( unsafePerformIO )
-import DATA_IOREF ( readIORef, writeIORef )
+import Control.Exception ( Exception(..), finally, catchDyn, throw )
+import qualified Control.Exception as Exception
+import Data.Dynamic ( Typeable )
+import Data.IORef ( IORef, newIORef )
+import System.IO.Unsafe ( unsafePerformIO )
+import Data.IORef ( readIORef, writeIORef )
-import qualified List ( elem, notElem )
+import qualified Data.List as List ( elem, notElem )
#ifndef DEBUG
-import List ( zipWith4 )
+import Data.List ( zipWith4 )
#endif
-import Monad ( when )
-import IO ( catch, isDoesNotExistError )
-import Directory ( doesDirectoryExist, createDirectory )
-import Char ( isUpper, isAlphaNum, isSpace, ord, isDigit )
-import Ratio ( (%) )
-import Time ( ClockTime )
-import Directory ( getModificationTime )
+import Control.Monad ( when )
+import SYSTEM_IO_ERROR as IO ( catch, isDoesNotExistError )
+import System.Directory ( doesDirectoryExist, createDirectory,
+ getModificationTime )
+import Data.Char ( isUpper, isAlphaNum, isSpace, ord, isDigit )
+import Data.Ratio ( (%) )
+import System.Time ( ClockTime )
infixr 9 `thenCmp`
\end{code}
%************************************************************************
%* *
-\subsection{The Eager monad}
-%* *
-%************************************************************************
-
-The @Eager@ monad is just an encoding of continuation-passing style,
-used to allow you to express "do this and then that", mainly to avoid
-space leaks. It's done with a type synonym to save bureaucracy.
-
-\begin{code}
-#if NOT_USED
-
-type Eager ans a = (a -> ans) -> ans
-
-runEager :: Eager a a -> a
-runEager m = m (\x -> x)
-
-appEager :: Eager ans a -> (a -> ans) -> ans
-appEager m cont = m cont
-
-thenEager :: Eager ans a -> (a -> Eager ans b) -> Eager ans b
-thenEager m k cont = m (\r -> k r cont)
-
-returnEager :: a -> Eager ans a
-returnEager v cont = cont v
-
-mapEager :: (a -> Eager ans b) -> [a] -> Eager ans [b]
-mapEager f [] = returnEager []
-mapEager f (x:xs) = f x `thenEager` \ y ->
- mapEager f xs `thenEager` \ ys ->
- returnEager (y:ys)
-#endif
-\end{code}
-
-%************************************************************************
-%* *
\subsection{A for loop}
%* *
%************************************************************************
filterOut p [] = []
filterOut p (x:xs) | p x = filterOut p xs
| otherwise = x : filterOut p xs
+
+partitionWith :: (a -> Either b c) -> [a] -> ([b], [c])
+partitionWith f [] = ([],[])
+partitionWith f (x:xs) = case f x of
+ Left b -> (b:bs, cs)
+ Right c -> (bs, c:cs)
+ where
+ (bs,cs) = partitionWith f xs
+
+splitEithers :: [Either a b] -> ([a], [b])
+splitEithers [] = ([],[])
+splitEithers (e : es) = case e of
+ Left x -> (x:xs, ys)
+ Right y -> (xs, y:ys)
+ where
+ (xs,ys) = splitEithers es
\end{code}
A paranoid @zip@ (and some @zipWith@ friends) that checks the lists
notNull [] = False
notNull _ = True
-snocView :: [a] -> Maybe ([a],a)
- -- Split off the last element
-snocView [] = Nothing
-snocView xs = go [] xs
- where
- -- Invariant: second arg is non-empty
- go acc [x] = Just (reverse acc, x)
- go acc (x:xs) = go (x:acc) xs
-
only :: [a] -> a
#ifdef DEBUG
only [a] = a
%* *
%************************************************************************
-@mapAccumL@ behaves like a combination
-of @map@ and @foldl@;
-it applies a function to each element of a list, passing an accumulating
-parameter from left to right, and returning a final value of this
-accumulator together with the new list.
-
-\begin{code}
-mapAccumL :: (acc -> x -> (acc, y)) -- Function of elt of input list
- -- and accumulator, returning new
- -- accumulator and elt of result list
- -> acc -- Initial accumulator
- -> [x] -- Input list
- -> (acc, [y]) -- Final accumulator and result list
-
-mapAccumL f b [] = (b, [])
-mapAccumL f b (x:xs) = (b'', x':xs') where
- (b', x') = f b x
- (b'', xs') = mapAccumL f b' xs
-\end{code}
-
-@mapAccumR@ does the same, but working from right to left instead. Its type is
-the same as @mapAccumL@, though.
-
-\begin{code}
-mapAccumR :: (acc -> x -> (acc, y)) -- Function of elt of input list
- -- and accumulator, returning new
- -- accumulator and elt of result list
- -> acc -- Initial accumulator
- -> [x] -- Input list
- -> (acc, [y]) -- Final accumulator and result list
-
-mapAccumR f b [] = (b, [])
-mapAccumR f b (x:xs) = (b'', x':xs') where
- (b'', x') = f b' x
- (b', xs') = mapAccumR f b xs
-\end{code}
-
-Here is the bi-directional version, that works from both left and right.
-
-\begin{code}
-mapAccumB :: (accl -> accr -> x -> (accl, accr,y))
- -- Function of elt of input list
- -- and accumulator, returning new
- -- accumulator and elt of result list
- -> accl -- Initial accumulator from left
- -> accr -- Initial accumulator from right
- -> [x] -- Input list
- -> (accl, accr, [y]) -- Final accumulators and result list
-
-mapAccumB f a b [] = (a,b,[])
-mapAccumB f a b (x:xs) = (a'',b'',y:ys)
- where
- (a',b'',y) = f a b' x
- (a'',b',ys) = mapAccumB f a' b xs
-\end{code}
-
-A strict version of foldl.
-
-\begin{code}
-foldl' :: (a -> b -> a) -> a -> [b] -> a
-foldl' f z xs = lgo z xs
- where
- lgo z [] = z
- lgo z (x:xs) = (lgo $! (f z x)) xs
-\end{code}
-
A combination of foldl with zip. It works with equal length lists.
\begin{code}
where
(ys', ys'') = splitAtList xs ys
+snocView :: [a] -> Maybe ([a],a)
+ -- Split off the last element
+snocView [] = Nothing
+snocView xs = go [] xs
+ where
+ -- Invariant: second arg is non-empty
+ go acc [x] = Just (reverse acc, x)
+ go acc (x:xs) = go (x:acc) xs
+
split :: Char -> String -> [String]
split c s = case rest of
[] -> [chunk]
\end{code}
\begin{code}
-prefixMatch :: Eq a => [a] -> [a] -> Bool
-prefixMatch [] _str = True
-prefixMatch _pat [] = False
-prefixMatch (p:ps) (s:ss) | p == s = prefixMatch ps ss
- | otherwise = False
-
maybePrefixMatch :: String -> String -> Maybe String
maybePrefixMatch [] rest = Just rest
maybePrefixMatch (_:_) [] = Nothing
| p == r = maybePrefixMatch pat rest
| otherwise = Nothing
-suffixMatch :: Eq a => [a] -> [a] -> Bool
-suffixMatch pat str = prefixMatch (reverse pat) (reverse str)
-
removeSpaces :: String -> String
removeSpaces = reverse . dropWhile isSpace . reverse . dropWhile isSpace
\end{code}
%* *
%************************************************************************
-The following are curried versions of @fst@ and @snd@.
-
-\begin{code}
-#if NOT_USED
-cfst :: a -> b -> a -- stranal-sem only (Note)
-cfst x y = x
-#endif
-\end{code}
-
-The following provide us higher order functions that, when applied
-to a function, operate on pairs.
-
-\begin{code}
-#if NOT_USED
-applyToPair :: ((a -> c),(b -> d)) -> (a,b) -> (c,d)
-applyToPair (f,g) (x,y) = (f x, g y)
-
-applyToFst :: (a -> c) -> (a,b)-> (c,b)
-applyToFst f (x,y) = (f x,y)
-
-applyToSnd :: (b -> d) -> (a,b) -> (a,d)
-applyToSnd f (x,y) = (x,f y)
-#endif
-\end{code}
-
\begin{code}
unzipWith :: (a -> b -> c) -> [(a, b)] -> [c]
unzipWith f pairs = map ( \ (a, b) -> f a b ) pairs
Module names:
\begin{code}
+looksLikeModuleName :: String -> Bool
looksLikeModuleName [] = False
looksLikeModuleName (c:cs) = isUpper c && go cs
where go [] = True
go (c:cs) = (isAlphaNum c || c == '_') && go cs
\end{code}
-Akin to @Prelude.words@, but sensitive to dquoted entities treating
-them as single words.
+Akin to @Prelude.words@, but acts like the Bourne shell, treating
+quoted strings and escaped characters within the input as solid blocks
+of characters. Doesn't raise any exceptions on malformed escapes or
+quoting.
\begin{code}
toArgs :: String -> [String]
toArgs "" = []
toArgs s =
- case break (\ ch -> isSpace ch || ch == '"') (dropWhile isSpace s) of -- "
- (w,aft) ->
- (\ ws -> if null w then ws else w : ws) $
- case aft of
- [] -> []
- (x:xs)
- | x /= '"' -> toArgs xs
- | otherwise ->
- case lex aft of
- ((str,rs):_) -> stripQuotes str : toArgs rs
- _ -> [aft]
+ case dropWhile isSpace s of -- drop initial spacing
+ [] -> [] -- empty, so no more tokens
+ rem -> let (tok,aft) = token rem [] in tok : toArgs aft
where
- -- strip away dquotes; assume first and last chars contain quotes.
- stripQuotes :: String -> String
- stripQuotes ('"':xs) = init xs
- stripQuotes xs = xs
+ -- Grab a token off the string, given that the first character exists and
+ -- isn't whitespace. The second argument is an accumulator which has to be
+ -- reversed at the end.
+ token [] acc = (reverse acc,[]) -- out of characters
+ token ('\\':c:aft) acc -- escapes
+ = token aft ((escape c) : acc)
+ token (q:aft) acc | q == '"' || q == '\'' -- open quotes
+ = let (aft',acc') = quote q aft acc in token aft' acc'
+ token (c:aft) acc | isSpace c -- unescaped, unquoted spacing
+ = (reverse acc,aft)
+ token (c:aft) acc -- anything else goes in the token
+ = token aft (c:acc)
+
+ -- Get the appropriate character for a single-character escape.
+ escape 'n' = '\n'
+ escape 't' = '\t'
+ escape 'r' = '\r'
+ escape c = c
+
+ -- Read into accumulator until a quote character is found.
+ quote qc =
+ let quote' [] acc = ([],acc)
+ quote' ('\\':c:aft) acc = quote' aft ((escape c) : acc)
+ quote' (c:aft) acc | c == qc = (aft,acc)
+ quote' (c:aft) acc = quote' aft (c:acc)
+ in quote'
\end{code}
-- -----------------------------------------------------------------------------
handleDyn = flip catchDyn
handle :: (Exception -> IO a) -> IO a -> IO a
-#if __GLASGOW_HASKELL__ < 501
-handle = flip Exception.catchAllIO
-#else
handle h f = f `Exception.catch` \e -> case e of
ExitException _ -> throw e
_ -> h e
-#endif
-- --------------------------------------------------------------
-- check existence & modification time at the same time
projects / ghc-hetmet.git / blobdiff