%
-% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
+% (c) The University of Glasgow 1992-2002
%
\section[Util]{Highly random utility functions}
\begin{code}
--- IF_NOT_GHC is meant to make this module useful outside the context of GHC
-#define IF_NOT_GHC(a)
-
module Util (
- -- The Eager monad
- Eager, thenEager, returnEager, mapEager, appEager, runEager,
-- general list processing
zipEqual, zipWithEqual, zipWith3Equal, zipWith4Equal,
- zipLazy, stretchZipEqual,
+ zipLazy, stretchZipWith,
mapAndUnzip, mapAndUnzip3,
- nOfThem, lengthExceeds, isSingleton, only,
- snocView,
- isIn, isn'tIn,
+ nOfThem, filterOut,
+ lengthExceeds, lengthIs, lengthAtLeast, listLengthCmp, atLength,
+ isSingleton, only,
+ notNull, snocView,
- -- association lists
- assoc, assocUsing, assocDefault, assocDefaultUsing,
+ isIn, isn'tIn,
- -- duplicate handling
- hasNoDups, equivClasses, runs, removeDups, equivClassesByUniq,
+ -- for-loop
+ nTimes,
-- sorting
- IF_NOT_GHC(quicksort COMMA stableSortLt COMMA mergesort COMMA)
- sortLt,
- IF_NOT_GHC(mergeSort COMMA) naturalMergeSortLe, -- from Carsten
- IF_NOT_GHC(naturalMergeSort COMMA mergeSortLe COMMA)
+ sortLt, naturalMergeSortLe,
-- transitive closures
transitiveClosure,
-- accumulating
- mapAccumL, mapAccumR, mapAccumB, foldl2, count,
+ mapAccumL, mapAccumR, mapAccumB,
+ foldl2, count,
+
+ takeList, dropList, splitAtList,
-- comparisons
- thenCmp, cmpList,
+ eqListBy, equalLength, compareLength,
+ thenCmp, cmpList, prefixMatch, suffixMatch, maybePrefixMatch,
-- strictness
- seqList, ($!),
+ foldl', seqList,
-- pairs
- IF_NOT_GHC(cfst COMMA applyToPair COMMA applyToFst COMMA)
- IF_NOT_GHC(applyToSnd COMMA foldPair COMMA)
- unzipWith
+ unzipWith,
+
+ global,
+
+ -- module names
+ looksLikeModuleName,
+
+ toArgs,
+
+ -- Floating point stuff
+ readRational,
) where
+#include "../includes/ghcconfig.h"
#include "HsVersions.h"
+import Panic ( panic, trace )
+import FastTypes
+
+#if __GLASGOW_HASKELL__ <= 408
+import EXCEPTION ( catchIO, justIoErrors, raiseInThread )
+#endif
+import DATA_IOREF ( IORef, newIORef )
+import UNSAFE_IO ( unsafePerformIO )
+
+import qualified List ( elem, notElem )
+
+#ifndef DEBUG
import List ( zipWith4 )
-import Panic ( panic )
-import Unique ( Unique )
-import UniqFM ( eltsUFM, emptyUFM, addToUFM_C )
+#endif
+
+import Char ( isUpper, isAlphaNum, isSpace, ord, isDigit )
+import Ratio ( (%) )
infixr 9 `thenCmp`
\end{code}
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
mapEager f (x:xs) = f x `thenEager` \ y ->
mapEager f xs `thenEager` \ ys ->
returnEager (y:ys)
+#endif
+\end{code}
+
+%************************************************************************
+%* *
+\subsection{A for loop}
+%* *
+%************************************************************************
+
+\begin{code}
+-- Compose a function with itself n times. (nth rather than twice)
+nTimes :: Int -> (a -> a) -> (a -> a)
+nTimes 0 _ = id
+nTimes 1 f = f
+nTimes n f = f . nTimes (n-1) f
\end{code}
%************************************************************************
%* *
%************************************************************************
+\begin{code}
+filterOut :: (a->Bool) -> [a] -> [a]
+-- Like filter, only reverses the sense of the test
+filterOut p [] = []
+filterOut p (x:xs) | p x = filterOut p xs
+ | otherwise = x : filterOut p xs
+\end{code}
+
A paranoid @zip@ (and some @zipWith@ friends) that checks the lists
are of equal length. Alastair Reid thinks this should only happen if
DEBUGging on; hey, why not?
\begin{code}
-stretchZipEqual :: (a -> b -> Maybe a) -> [a] -> [b] -> [a]
--- (stretchZipEqual f xs ys) stretches ys to "fit" the places where f returns a Just
+stretchZipWith :: (a -> Bool) -> b -> (a->b->c) -> [a] -> [b] -> [c]
+-- (stretchZipWith p z f xs ys) stretches ys by inserting z in
+-- the places where p returns *True*
-stretchZipEqual f [] [] = []
-stretchZipEqual f (x:xs) (y:ys) = case f x y of
- Just x' -> x' : stretchZipEqual f xs ys
- Nothing -> x : stretchZipEqual f xs (y:ys)
+stretchZipWith p z f [] ys = []
+stretchZipWith p z f (x:xs) ys
+ | p x = f x z : stretchZipWith p z f xs ys
+ | otherwise = case ys of
+ [] -> []
+ (y:ys) -> f x y : stretchZipWith p z f xs ys
\end{code}
nOfThem :: Int -> a -> [a]
nOfThem n thing = replicate n thing
+-- 'atLength atLen atEnd ls n' unravels list 'ls' to position 'n';
+-- specification:
+--
+-- atLength atLenPred atEndPred ls n
+-- | n < 0 = atLenPred n
+-- | length ls < n = atEndPred (n - length ls)
+-- | otherwise = atLenPred (drop n ls)
+--
+atLength :: ([a] -> b)
+ -> (Int -> b)
+ -> [a]
+ -> Int
+ -> b
+atLength atLenPred atEndPred ls n
+ | n < 0 = atEndPred n
+ | otherwise = go n ls
+ where
+ go n [] = atEndPred n
+ go 0 ls = atLenPred ls
+ go n (_:xs) = go (n-1) xs
+
+-- special cases.
lengthExceeds :: [a] -> Int -> Bool
--- (lengthExceeds xs n) is True if length xs > n
-(x:xs) `lengthExceeds` n = n < 1 || xs `lengthExceeds` (n - 1)
-[] `lengthExceeds` n = n < 0
+-- (lengthExceeds xs n) = (length xs > n)
+lengthExceeds = atLength notNull (const False)
+
+lengthAtLeast :: [a] -> Int -> Bool
+lengthAtLeast = atLength notNull (== 0)
+
+lengthIs :: [a] -> Int -> Bool
+lengthIs = atLength null (==0)
+
+listLengthCmp :: [a] -> Int -> Ordering
+listLengthCmp = atLength atLen atEnd
+ where
+ atEnd 0 = EQ
+ atEnd x
+ | x > 0 = LT -- not yet seen 'n' elts, so list length is < n.
+ | otherwise = GT
+
+ atLen [] = EQ
+ atLen _ = GT
isSingleton :: [a] -> Bool
isSingleton [x] = True
isSingleton _ = False
+notNull :: [a] -> Bool
+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
#endif
\end{code}
-\begin{code}
-snocView :: [a] -> ([a], a) -- Split off the last element
-snocView xs = go xs []
- where
- go [x] acc = (reverse acc, x)
- go (x:xs) acc = go xs (x:acc)
-\end{code}
-
Debugging/specialising versions of \tr{elem} and \tr{notElem}
\begin{code}
notElem__ x [] = True
notElem__ x (y:ys) = x /= y && notElem__ x ys
-# else {- DEBUG -}
+# else /* DEBUG */
isIn msg x ys
- = elem ILIT(0) x ys
+ = elem (_ILIT 0) x ys
where
elem i _ [] = False
elem i x (y:ys)
- | i _GE_ ILIT(100) = panic ("Over-long elem in: " ++ msg)
- | otherwise = x == y || elem (i _ADD_ ILIT(1)) x ys
+ | i ># _ILIT 100 = trace ("Over-long elem in " ++ msg) $
+ x `List.elem` (y:ys)
+ | otherwise = x == y || elem (i +# _ILIT(1)) x ys
isn'tIn msg x ys
- = notElem ILIT(0) x ys
+ = notElem (_ILIT 0) x ys
where
notElem i x [] = True
notElem i x (y:ys)
- | i _GE_ ILIT(100) = panic ("Over-long notElem in: " ++ msg)
- | otherwise = x /= y && notElem (i _ADD_ ILIT(1)) x ys
-
-# endif {- DEBUG -}
-
-\end{code}
-
-%************************************************************************
-%* *
-\subsection[Utils-assoc]{Association lists}
-%* *
-%************************************************************************
-
-See also @assocMaybe@ and @mkLookupFun@ in module @Maybes@.
-
-\begin{code}
-assoc :: (Eq a) => String -> [(a, b)] -> a -> b
-assocDefault :: (Eq a) => b -> [(a, b)] -> a -> b
-assocUsing :: (a -> a -> Bool) -> String -> [(a, b)] -> a -> b
-assocDefaultUsing :: (a -> a -> Bool) -> b -> [(a, b)] -> a -> b
-
-assocDefaultUsing eq deflt ((k,v) : rest) key
- | k `eq` key = v
- | otherwise = assocDefaultUsing eq deflt rest key
-
-assocDefaultUsing eq deflt [] key = deflt
-
-assoc crash_msg list key = assocDefaultUsing (==) (panic ("Failed in assoc: " ++ crash_msg)) list key
-assocDefault deflt list key = assocDefaultUsing (==) deflt list key
-assocUsing eq crash_msg list key = assocDefaultUsing eq (panic ("Failed in assoc: " ++ crash_msg)) list key
-\end{code}
-
-%************************************************************************
-%* *
-\subsection[Utils-dups]{Duplicate-handling}
-%* *
-%************************************************************************
-
-\begin{code}
-hasNoDups :: (Eq a) => [a] -> Bool
-
-hasNoDups xs = f [] xs
- where
- f seen_so_far [] = True
- f seen_so_far (x:xs) = if x `is_elem` seen_so_far then
- False
- else
- f (x:seen_so_far) xs
-
- is_elem = isIn "hasNoDups"
-\end{code}
-
-\begin{code}
-equivClasses :: (a -> a -> Ordering) -- Comparison
- -> [a]
- -> [[a]]
-
-equivClasses cmp stuff@[] = []
-equivClasses cmp stuff@[item] = [stuff]
-equivClasses cmp items
- = runs eq (sortLt lt items)
- where
- eq a b = case cmp a b of { EQ -> True; _ -> False }
- lt a b = case cmp a b of { LT -> True; _ -> False }
-\end{code}
-
-The first cases in @equivClasses@ above are just to cut to the point
-more quickly...
-
-@runs@ groups a list into a list of lists, each sublist being a run of
-identical elements of the input list. It is passed a predicate @p@ which
-tells when two elements are equal.
-
-\begin{code}
-runs :: (a -> a -> Bool) -- Equality
- -> [a]
- -> [[a]]
-
-runs p [] = []
-runs p (x:xs) = case (span (p x) xs) of
- (first, rest) -> (x:first) : (runs p rest)
-\end{code}
-
-\begin{code}
-removeDups :: (a -> a -> Ordering) -- Comparison function
- -> [a]
- -> ([a], -- List with no duplicates
- [[a]]) -- List of duplicate groups. One representative from
- -- each group appears in the first result
-
-removeDups cmp [] = ([], [])
-removeDups cmp [x] = ([x],[])
-removeDups cmp xs
- = case (mapAccumR collect_dups [] (equivClasses cmp xs)) of { (dups, xs') ->
- (xs', dups) }
- where
- collect_dups dups_so_far [x] = (dups_so_far, x)
- collect_dups dups_so_far dups@(x:xs) = (dups:dups_so_far, x)
-\end{code}
-
-
-\begin{code}
-equivClassesByUniq :: (a -> Unique) -> [a] -> [[a]]
- -- NB: it's *very* important that if we have the input list [a,b,c],
- -- where a,b,c all have the same unique, then we get back the list
- -- [a,b,c]
- -- not
- -- [c,b,a]
- -- Hence the use of foldr, plus the reversed-args tack_on below
-equivClassesByUniq get_uniq xs
- = eltsUFM (foldr add emptyUFM xs)
- where
- add a ufm = addToUFM_C tack_on ufm (get_uniq a) [a]
- tack_on old new = new++old
+ | i ># _ILIT 100 = trace ("Over-long notElem in " ++ msg) $
+ x `List.notElem` (y:ys)
+ | otherwise = x /= y && notElem (i +# _ILIT(1)) x ys
+# endif /* DEBUG */
\end{code}
%************************************************************************
%************************************************************************
\begin{code}
+#if NOT_USED
+
-- tail-recursive, etc., "quicker sort" [as per Meira thesis]
quicksort :: (a -> a -> Bool) -- Less-than predicate
-> [a] -- Input list
split x lo hi [] = quicksort lt lo ++ (x : quicksort lt hi)
split x lo hi (y:ys) | y `lt` x = split x (y:lo) hi ys
| True = split x lo (y:hi) ys
+#endif
\end{code}
Quicksort variant from Lennart's Haskell-library contribution. This
is a {\em stable} sort.
\begin{code}
-stableSortLt = sortLt -- synonym; when we want to highlight stable-ness
-
sortLt :: (a -> a -> Bool) -- Less-than predicate
-> [a] -- Input list
-> [a] -- Result list
%************************************************************************
\begin{code}
+#if NOT_USED
mergesort :: (a -> a -> Ordering) -> [a] -> [a]
mergesort cmp xs = merge_lists (split_into_runs [] xs)
EQ -> x : y : (merge xs ys)
LT -> x : (merge xs yl)
GT -> y : (merge xl ys)
+#endif
\end{code}
%************************************************************************
balancedFold' f (x:y:xs) = f x y : balancedFold' f xs
balancedFold' f xs = xs
-generalMergeSort p [] = []
-generalMergeSort p xs = (balancedFold (generalMerge p) . map (: [])) xs
-
generalNaturalMergeSort p [] = []
generalNaturalMergeSort p xs = (balancedFold (generalMerge p) . group p) xs
+#if NOT_USED
+generalMergeSort p [] = []
+generalMergeSort p xs = (balancedFold (generalMerge p) . map (: [])) xs
+
mergeSort, naturalMergeSort :: Ord a => [a] -> [a]
mergeSort = generalMergeSort (<=)
naturalMergeSort = generalNaturalMergeSort (<=)
mergeSortLe le = generalMergeSort le
+#endif
+
naturalMergeSortLe le = generalNaturalMergeSort le
\end{code}
(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}
| otherwise = count p xs
\end{code}
+@splitAt@, @take@, and @drop@ but with length of another
+list giving the break-off point:
+
+\begin{code}
+takeList :: [b] -> [a] -> [a]
+takeList [] _ = []
+takeList (_:xs) ls =
+ case ls of
+ [] -> []
+ (y:ys) -> y : takeList xs ys
+
+dropList :: [b] -> [a] -> [a]
+dropList [] xs = xs
+dropList _ xs@[] = xs
+dropList (_:xs) (_:ys) = dropList xs ys
+
+
+splitAtList :: [b] -> [a] -> ([a], [a])
+splitAtList [] xs = ([], xs)
+splitAtList _ xs@[] = (xs, xs)
+splitAtList (_:xs) (y:ys) = (y:ys', ys'')
+ where
+ (ys', ys'') = splitAtList xs ys
+
+\end{code}
+
%************************************************************************
%* *
%************************************************************************
\begin{code}
+eqListBy :: (a->a->Bool) -> [a] -> [a] -> Bool
+eqListBy eq [] [] = True
+eqListBy eq (x:xs) (y:ys) = eq x y && eqListBy eq xs ys
+eqListBy eq xs ys = False
+
+equalLength :: [a] -> [b] -> Bool
+equalLength [] [] = True
+equalLength (_:xs) (_:ys) = equalLength xs ys
+equalLength xs ys = False
+
+compareLength :: [a] -> [b] -> Ordering
+compareLength [] [] = EQ
+compareLength (_:xs) (_:ys) = compareLength xs ys
+compareLength [] _ys = LT
+compareLength _xs [] = GT
+
thenCmp :: Ordering -> Ordering -> Ordering
{-# INLINE thenCmp #-}
thenCmp EQ any = any
\end{code}
\begin{code}
-cmpString :: String -> String -> Ordering
+prefixMatch :: Eq a => [a] -> [a] -> Bool
+prefixMatch [] _str = True
+prefixMatch _pat [] = False
+prefixMatch (p:ps) (s:ss) | p == s = prefixMatch ps ss
+ | otherwise = False
-cmpString [] [] = EQ
-cmpString (x:xs) (y:ys) = if x == y then cmpString xs ys
- else if x < y then LT
- else GT
-cmpString [] ys = LT
-cmpString xs [] = GT
-\end{code}
+maybePrefixMatch :: String -> String -> Maybe String
+maybePrefixMatch [] rest = Just rest
+maybePrefixMatch (_:_) [] = Nothing
+maybePrefixMatch (p:pat) (r:rest)
+ | p == r = maybePrefixMatch pat rest
+ | otherwise = Nothing
+suffixMatch :: Eq a => [a] -> [a] -> Bool
+suffixMatch pat str = prefixMatch (reverse pat) (reverse str)
+\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)
applyToSnd :: (b -> d) -> (a,b) -> (a,d)
applyToSnd f (x,y) = (x,f y)
-
-foldPair :: (a->a->a,b->b->b) -> (a,b) -> [(a,b)] -> (a,b)
-foldPair fg ab [] = ab
-foldPair fg@(f,g) ab ((a,b):abs) = (f a u,g b v)
- where (u,v) = foldPair fg ab abs
+#endif
\end{code}
\begin{code}
\end{code}
\begin{code}
-#if __HASKELL1__ > 4
seqList :: [a] -> b -> b
-#else
-seqList :: (Eval a) => [a] -> b -> b
-#endif
seqList [] b = b
seqList (x:xs) b = x `seq` seqList xs b
+\end{code}
-#if __HASKELL1__ <= 4
-($!) :: (Eval a) => (a -> b) -> a -> b
-f $! x = x `seq` f x
-#endif
+Global variables:
+
+\begin{code}
+global :: a -> IORef a
+global a = unsafePerformIO (newIORef a)
\end{code}
+Module names:
+
\begin{code}
-#if __GLASGOW_HASKELL__ < 402
-bracket :: IO a -> (a -> IO b) -> (a -> IO c) -> IO c
-bracket before after thing = do
- a <- before
- (thing a) `catch` (\err -> after a >>= fail err)
- after a
-#endif
+looksLikeModuleName [] = False
+looksLikeModuleName (c:cs) = isUpper c && go cs
+ where go [] = True
+ go ('.':cs) = looksLikeModuleName cs
+ go (c:cs) = (isAlphaNum c || c == '_') && go cs
+\end{code}
+
+Akin to @Prelude.words@, but sensitive to dquoted entities treating
+them as single words.
+
+\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]
+ where
+ -- strip away dquotes; assume first and last chars contain quotes.
+ stripQuotes :: String -> String
+ stripQuotes ('"':xs) = init xs
+ stripQuotes xs = xs
+\end{code}
+
+-- -----------------------------------------------------------------------------
+-- Floats
+
+\begin{code}
+readRational__ :: ReadS Rational -- NB: doesn't handle leading "-"
+readRational__ r = do
+ (n,d,s) <- readFix r
+ (k,t) <- readExp s
+ return ((n%1)*10^^(k-d), t)
+ where
+ readFix r = do
+ (ds,s) <- lexDecDigits r
+ (ds',t) <- lexDotDigits s
+ return (read (ds++ds'), length ds', t)
+
+ readExp (e:s) | e `elem` "eE" = readExp' s
+ readExp s = return (0,s)
+
+ readExp' ('+':s) = readDec s
+ readExp' ('-':s) = do
+ (k,t) <- readDec s
+ return (-k,t)
+ readExp' s = readDec s
+
+ readDec s = do
+ (ds,r) <- nonnull isDigit s
+ return (foldl1 (\n d -> n * 10 + d) [ ord d - ord '0' | d <- ds ],
+ r)
+
+ lexDecDigits = nonnull isDigit
+
+ lexDotDigits ('.':s) = return (span isDigit s)
+ lexDotDigits s = return ("",s)
+
+ nonnull p s = do (cs@(_:_),t) <- return (span p s)
+ return (cs,t)
+
+readRational :: String -> Rational -- NB: *does* handle a leading "-"
+readRational top_s
+ = case top_s of
+ '-' : xs -> - (read_me xs)
+ xs -> read_me xs
+ where
+ read_me s
+ = case (do { (x,"") <- readRational__ s ; return x }) of
+ [x] -> x
+ [] -> error ("readRational: no parse:" ++ top_s)
+ _ -> error ("readRational: ambiguous parse:" ++ top_s)
\end{code}
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