%
-% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996
+% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section[Util]{Highly random utility functions}
\begin{code}
-#if defined(COMPILING_GHC)
-# include "HsVersions.h"
-# define IF_NOT_GHC(a) {--}
-#else
-# define panic error
-# define TAG_ Ordering
-# define LT_ LT
-# define EQ_ EQ
-# define GT_ GT
-# define _LT LT
-# define _EQ EQ
-# define _GT GT
-# define GT__ _
-# define tagCmp_ compare
-# define _tagCmp compare
-# define FAST_STRING String
-# define ASSERT(x) {-nothing-}
-# define IF_NOT_GHC(a) a
-# define COMMA ,
-#endif
-
-#ifndef __GLASGOW_HASKELL__
-# undef TAG_
-# undef LT_
-# undef EQ_
-# undef GT_
-# undef tagCmp_
-#endif
+-- IF_NOT_GHC is meant to make this module useful outside the context of GHC
+#define IF_NOT_GHC(a)
module Util (
- -- Haskell-version support
-#ifndef __GLASGOW_HASKELL__
- tagCmp_,
- TAG_(..),
-#endif
+ -- The Eager monad
+ Eager, thenEager, returnEager, mapEager, appEager, runEager,
+
-- general list processing
IF_NOT_GHC(forall COMMA exists COMMA)
zipEqual, zipWithEqual, zipWith3Equal, zipWith4Equal,
- zipLazy,
+ zipLazy, stretchZipEqual,
mapAndUnzip, mapAndUnzip3,
nOfThem, lengthExceeds, isSingleton,
-#if defined(COMPILING_GHC)
- startsWith, endsWith,
+ snocView,
isIn, isn'tIn,
-#endif
-- association lists
- assoc,
+ assoc, assocUsing, assocDefault, assocDefaultUsing,
-- duplicate handling
- hasNoDups, equivClasses, runs, removeDups,
+ hasNoDups, equivClasses, runs, removeDups, equivClassesByUniq,
-- sorting
IF_NOT_GHC(quicksort COMMA stableSortLt COMMA mergesort COMMA)
mapAccumL, mapAccumR, mapAccumB,
-- comparisons
-#if defined(COMPILING_GHC)
- Ord3(..), thenCmp, cmpList,
- cmpPString,
-#else
- cmpString,
-#endif
+ thenCmp, cmpList,
-- pairs
IF_NOT_GHC(cfst COMMA applyToPair COMMA applyToFst COMMA)
IF_NOT_GHC(applyToSnd COMMA foldPair COMMA)
unzipWith
-
- -- error handling
-#if defined(COMPILING_GHC)
- , panic, panic#, pprPanic, pprPanic#, pprError, pprTrace
- , assertPanic
-#endif {- COMPILING_GHC -}
-
) where
-#if defined(COMPILING_GHC)
-
-CHK_Ubiq() -- debugging consistency check
-IMPORT_1_3(List(zipWith4))
+#include "HsVersions.h"
-import Pretty
-#else
-import List(zipWith4)
-#endif
+import List ( zipWith4 )
+import Panic ( panic )
+import Unique ( Unique )
+import UniqFM ( eltsUFM, emptyUFM, addToUFM_C )
infixr 9 `thenCmp`
\end{code}
%************************************************************************
%* *
-\subsection[Utils-version-support]{Functions to help pre-1.2 versions of (non-Glasgow) Haskell}
+\subsection{The Eager monad}
%* *
%************************************************************************
-This is our own idea:
+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}
-#ifndef __GLASGOW_HASKELL__
-data TAG_ = LT_ | EQ_ | GT_
+type Eager ans a = (a -> ans) -> ans
-tagCmp_ :: Ord a => a -> a -> TAG_
-tagCmp_ a b = if a == b then EQ_ else if a < b then LT_ else GT_
-#endif
+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)
\end{code}
%************************************************************************
zipLazy (x:xs) ~(y:ys) = (x,y) : zipLazy xs ys
\end{code}
+
+\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
+
+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)
+\end{code}
+
+
\begin{code}
mapAndUnzip :: (a -> (b, c)) -> [a] -> ([b], [c])
isSingleton [x] = True
isSingleton _ = False
+\end{code}
-startsWith, endsWith :: String -> String -> Maybe String
-
-startsWith [] str = Just str
-startsWith (c:cs) (s:ss)
- = if c /= s then Nothing else startsWith cs ss
-startsWith _ [] = Nothing
-
-endsWith cs ss
- = case (startsWith (reverse cs) (reverse ss)) of
- Nothing -> Nothing
- Just rs -> Just (reverse rs)
+\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}
-#if defined(COMPILING_GHC)
isIn, isn'tIn :: (Eq a) => String -> a -> [a] -> Bool
# ifndef DEBUG
# endif {- DEBUG -}
-#endif {- COMPILING_GHC -}
\end{code}
%************************************************************************
See also @assocMaybe@ and @mkLookupFun@ in module @Maybes@.
\begin{code}
-assoc :: (Eq a) => String -> [(a, b)] -> a -> b
+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
-assoc crash_msg lst key
- = if (null res)
- then panic ("Failed in assoc: " ++ crash_msg)
- else head res
- where res = [ val | (key', val) <- lst, key == 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}
%************************************************************************
else
f (x:seen_so_far) xs
-#if defined(COMPILING_GHC)
is_elem = isIn "hasNoDups"
-#else
- is_elem = elem
-#endif
\end{code}
\begin{code}
-equivClasses :: (a -> a -> TAG_) -- Comparison
+equivClasses :: (a -> a -> Ordering) -- Comparison
-> [a]
-> [[a]]
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 }
+ 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
\end{code}
\begin{code}
-removeDups :: (a -> a -> TAG_) -- Comparison function
+removeDups :: (a -> a -> Ordering) -- Comparison function
-> [a]
-> ([a], -- List with no duplicates
[[a]]) -- List of duplicate groups. One representative from
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
+\end{code}
+
%************************************************************************
%* *
\subsection[Utils-sorting]{Sorting}
%************************************************************************
\begin{code}
-mergesort :: (a -> a -> TAG_) -> [a] -> [a]
+mergesort :: (a -> a -> Ordering) -> [a] -> [a]
mergesort cmp xs = merge_lists (split_into_runs [] xs)
where
- a `le` b = case cmp a b of { LT_ -> True; EQ_ -> True; GT__ -> False }
- a `ge` b = case cmp a b of { LT_ -> False; EQ_ -> True; GT__ -> True }
+ a `le` b = case cmp a b of { LT -> True; EQ -> True; GT -> False }
+ a `ge` b = case cmp a b of { LT -> False; EQ -> True; GT -> True }
split_into_runs [] [] = []
split_into_runs run [] = [run]
merge xs [] = xs
merge xl@(x:xs) yl@(y:ys)
= case cmp x y of
- EQ_ -> x : y : (merge xs ys)
- LT_ -> x : (merge xs yl)
- GT__ -> y : (merge xl ys)
+ EQ -> x : y : (merge xs ys)
+ LT -> x : (merge xs yl)
+ GT -> y : (merge xl ys)
\end{code}
%************************************************************************
%* *
%************************************************************************
-See also @tagCmp_@ near the versions-compatibility section.
-
-The Ord3 class will be subsumed into Ord in Haskell 1.3.
-
\begin{code}
-class Ord3 a where
- cmp :: a -> a -> TAG_
-
-thenCmp :: TAG_ -> TAG_ -> TAG_
+thenCmp :: Ordering -> Ordering -> Ordering
{-# INLINE thenCmp #-}
-thenCmp EQ_ any = any
+thenCmp EQ any = any
thenCmp other any = other
-cmpList :: (a -> a -> TAG_) -> [a] -> [a] -> TAG_
+cmpList :: (a -> a -> Ordering) -> [a] -> [a] -> Ordering
-- `cmpList' uses a user-specified comparer
-cmpList cmp [] [] = EQ_
-cmpList cmp [] _ = LT_
-cmpList cmp _ [] = GT_
+cmpList cmp [] [] = EQ
+cmpList cmp [] _ = LT
+cmpList cmp _ [] = GT
cmpList cmp (a:as) (b:bs)
- = case cmp a b of { EQ_ -> cmpList cmp as bs; xxx -> xxx }
-\end{code}
-
-\begin{code}
-instance Ord3 a => Ord3 [a] where
- cmp [] [] = EQ_
- cmp (x:xs) [] = GT_
- cmp [] (y:ys) = LT_
- cmp (x:xs) (y:ys) = (x `cmp` y) `thenCmp` (xs `cmp` ys)
-
-instance Ord3 a => Ord3 (Maybe a) where
- cmp Nothing Nothing = EQ_
- cmp Nothing (Just y) = LT_
- cmp (Just x) Nothing = GT_
- cmp (Just x) (Just y) = x `cmp` y
-
-instance Ord3 Int where
- cmp a b | a < b = LT_
- | a > b = GT_
- | otherwise = EQ_
+ = case cmp a b of { EQ -> cmpList cmp as bs; xxx -> xxx }
\end{code}
\begin{code}
-cmpString :: String -> String -> TAG_
+cmpString :: String -> String -> Ordering
-cmpString [] [] = EQ_
+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_
+ else if x < y then LT
+ else GT
+cmpString [] ys = LT
+cmpString xs [] = GT
-#ifdef COMPILING_GHC
-cmpString _ _ = panic# "cmpString"
-#else
-cmpString _ _ = error "cmpString"
-#endif
+cmpString _ _ = panic "cmpString"
\end{code}
-\begin{code}
-cmpPString :: FAST_STRING -> FAST_STRING -> TAG_
-
-cmpPString x y
- = case (_tagCmp x y) of { _LT -> LT_ ; _EQ -> EQ_ ; _GT -> GT_ }
-\end{code}
+y
%************************************************************************
%* *
\subsection[Utils-pairs]{Pairs}
unzipWith f pairs = map ( \ (a, b) -> f a b ) pairs
\end{code}
-%************************************************************************
-%* *
-\subsection[Utils-errors]{Error handling}
-%* *
-%************************************************************************
-
-\begin{code}
-#if defined(COMPILING_GHC)
-panic x = error ("panic! (the `impossible' happened):\n\t"
- ++ x ++ "\n\n"
- ++ "Please report it as a compiler bug "
- ++ "to glasgow-haskell-bugs@dcs.gla.ac.uk.\n\n" )
-
-pprPanic heading pretty_msg = panic (heading++(ppShow 80 pretty_msg))
-pprError heading pretty_msg = error (heading++(ppShow 80 pretty_msg))
-#if __GLASGOW_HASKELL__ >= 200
-pprTrace heading pretty_msg = GHCbase.trace (heading++(ppShow 80 pretty_msg))
-#else
-pprTrace heading pretty_msg = trace (heading++(ppShow 80 pretty_msg))
-#endif
-
--- #-versions because panic can't return an unboxed int, and that's
--- what TAG_ is with GHC at the moment. Ugh. (Simon)
--- No, man -- Too Beautiful! (Will)
-panic# :: String -> TAG_
-panic# s = case (panic s) of () -> EQ_
-
-pprPanic# heading pretty_msg = panic# (heading++(ppShow 80 pretty_msg))
-
-assertPanic :: String -> Int -> a
-assertPanic file line = panic ("ASSERT failed! file "++file++", line "++show line)
-
-#endif {- COMPILING_GHC -}
-\end{code}
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