-- (c) The University of Glasgow 2006
{-# LANGUAGE CPP #-}
{-# LANGUAGE KindSignatures #-}
{-# LANGUAGE ConstraintKinds #-}
{-# LANGUAGE BangPatterns #-}
{-# LANGUAGE TupleSections #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE MagicHash #-}
{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}
-- | Highly random utility functions
--
module GHC.Utils.Misc (
-- * Flags dependent on the compiler build
ghciSupported, debugIsOn,
isWindowsHost, isDarwinHost,
-- * Miscellaneous higher-order functions
applyWhen, nTimes,
-- * General list processing
zipEqual, zipWithEqual, zipWith3Equal, zipWith4Equal,
zipLazy, stretchZipWith, zipWithAndUnzip, zipAndUnzip,
zipWithLazy, zipWith3Lazy,
filterByList, filterByLists, partitionByList,
unzipWith,
mapFst, mapSnd, chkAppend,
mapAndUnzip, mapAndUnzip3,
filterOut, partitionWith,
dropWhileEndLE, spanEnd, last2, lastMaybe,
List.foldl1', foldl2, count, countWhile, all2,
lengthExceeds, lengthIs, lengthIsNot,
lengthAtLeast, lengthAtMost, lengthLessThan,
listLengthCmp, atLength,
equalLength, compareLength, leLength, ltLength,
isSingleton, only, GHC.Utils.Misc.singleton,
notNull, snocView,
isIn, isn'tIn,
chunkList,
changeLast,
mapLastM,
whenNonEmpty,
mergeListsBy,
isSortedBy,
-- * Tuples
fstOf3, sndOf3, thdOf3,
firstM, first3M, secondM,
fst3, snd3, third3,
uncurry3,
liftFst, liftSnd,
-- * List operations controlled by another list
takeList, dropList, splitAtList, split,
dropTail, capitalise,
-- * Sorting
sortWith, minWith, nubSort, ordNub,
-- * Comparisons
isEqual, eqListBy, eqMaybeBy,
thenCmp, cmpList,
removeSpaces,
(<&&>), (<||>),
-- * Edit distance
fuzzyMatch, fuzzyLookup,
-- * Transitive closures
transitiveClosure,
-- * Strictness
seqList, strictMap,
-- * Module names
looksLikeModuleName,
looksLikePackageName,
-- * Argument processing
getCmd, toCmdArgs, toArgs,
-- * Integers
exactLog2,
-- * Floating point
readRational,
readSignificandExponentPair,
readHexRational,
readHexSignificandExponentPair,
-- * IO-ish utilities
doesDirNameExist,
getModificationUTCTime,
modificationTimeIfExists,
withAtomicRename,
-- * Filenames and paths
Suffix,
splitLongestPrefix,
escapeSpaces,
Direction(..), reslash,
makeRelativeTo,
-- * Utils for defining Data instances
abstractConstr, abstractDataType, mkNoRepType,
-- * Utils for printing C code
charToC,
-- * Hashing
hashString,
-- * Call stacks
HasCallStack,
HasDebugCallStack,
-- * Utils for flags
OverridingBool(..),
overrideWith,
) where
#include "HsVersions.h"
import GHC.Prelude
import GHC.Utils.Exception
import GHC.Utils.Panic.Plain
import Data.Data
import qualified Data.List as List
import Data.List.NonEmpty ( NonEmpty(..) )
import GHC.Exts
import GHC.Stack (HasCallStack)
import Control.Applicative ( liftA2 )
import Control.Monad ( liftM, guard )
import Control.Monad.IO.Class ( MonadIO, liftIO )
import System.IO.Error as IO ( isDoesNotExistError )
import System.Directory ( doesDirectoryExist, getModificationTime, renameFile )
import System.FilePath
import Data.Char ( isUpper, isAlphaNum, isSpace, chr, ord, isDigit, toUpper
, isHexDigit, digitToInt )
import Data.Int
import Data.Ratio ( (%) )
import Data.Ord ( comparing )
import Data.Word
import qualified Data.IntMap as IM
import qualified Data.Set as Set
import Data.Time
#if defined(DEBUG)
import {-# SOURCE #-} GHC.Utils.Outputable ( text )
import {-# SOURCE #-} GHC.Driver.Ppr ( warnPprTrace )
#endif
infixr 9 `thenCmp`
{-
************************************************************************
* *
\subsection{Is DEBUG on, are we on Windows, etc?}
* *
************************************************************************
These booleans are global constants, set by CPP flags. They allow us to
recompile a single module (this one) to change whether or not debug output
appears. They sometimes let us avoid even running CPP elsewhere.
It's important that the flags are literal constants (True/False). Then,
with -0, tests of the flags in other modules will simplify to the correct
branch of the conditional, thereby dropping debug code altogether when
the flags are off.
-}
ghciSupported :: Bool
#if defined(HAVE_INTERNAL_INTERPRETER)
ghciSupported = True
#else
ghciSupported = False
#endif
debugIsOn :: Bool
#if defined(DEBUG)
debugIsOn = True
#else
debugIsOn = False
#endif
isWindowsHost :: Bool
#if defined(mingw32_HOST_OS)
isWindowsHost = True
#else
isWindowsHost = False
#endif
isDarwinHost :: Bool
#if defined(darwin_HOST_OS)
isDarwinHost = True
#else
isDarwinHost = False
#endif
{-
************************************************************************
* *
\subsection{Miscellaneous higher-order functions}
* *
************************************************************************
-}
-- | Apply a function iff some condition is met.
applyWhen :: Bool -> (a -> a) -> a -> a
applyWhen True f x = f x
applyWhen _ _ x = x
-- | Apply a function @n@ times to a given value.
nTimes :: Int -> (a -> a) -> (a -> a)
nTimes 0 _ = id
nTimes 1 f = f
nTimes n f = f . nTimes (n-1) f
fstOf3 :: (a,b,c) -> a
sndOf3 :: (a,b,c) -> b
thdOf3 :: (a,b,c) -> c
fstOf3 (a,_,_) = a
sndOf3 (_,b,_) = b
thdOf3 (_,_,c) = c
fst3 :: (a -> d) -> (a, b, c) -> (d, b, c)
fst3 f (a, b, c) = (f a, b, c)
snd3 :: (b -> d) -> (a, b, c) -> (a, d, c)
snd3 f (a, b, c) = (a, f b, c)
third3 :: (c -> d) -> (a, b, c) -> (a, b, d)
third3 f (a, b, c) = (a, b, f c)
uncurry3 :: (a -> b -> c -> d) -> (a, b, c) -> d
uncurry3 f (a, b, c) = f a b c
liftFst :: (a -> b) -> (a, c) -> (b, c)
liftFst f (a,c) = (f a, c)
liftSnd :: (a -> b) -> (c, a) -> (c, b)
liftSnd f (c,a) = (c, f a)
firstM :: Monad m => (a -> m c) -> (a, b) -> m (c, b)
firstM f (x, y) = liftM (\x' -> (x', y)) (f x)
first3M :: Monad m => (a -> m d) -> (a, b, c) -> m (d, b, c)
first3M f (x, y, z) = liftM (\x' -> (x', y, z)) (f x)
secondM :: Monad m => (b -> m c) -> (a, b) -> m (a, c)
secondM f (x, y) = (x,) <$> f y
{-
************************************************************************
* *
\subsection[Utils-lists]{General list processing}
* *
************************************************************************
-}
filterOut :: (a->Bool) -> [a] -> [a]
-- ^ Like filter, only it reverses the sense of the test
filterOut _ [] = []
filterOut p (x:xs) | p x = filterOut p xs
| otherwise = x : filterOut p xs
partitionWith :: (a -> Either b c) -> [a] -> ([b], [c])
-- ^ Uses a function to determine which of two output lists an input element should join
partitionWith _ [] = ([],[])
partitionWith f (x:xs) = case f x of
Left b -> (b:bs, cs)
Right c -> (bs, c:cs)
where (bs,cs) = partitionWith f xs
chkAppend :: [a] -> [a] -> [a]
-- Checks for the second argument being empty
-- Used in situations where that situation is common
chkAppend xs ys
| null ys = xs
| otherwise = xs ++ ys
{-
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?
-}
zipEqual :: String -> [a] -> [b] -> [(a,b)]
zipWithEqual :: String -> (a->b->c) -> [a]->[b]->[c]
zipWith3Equal :: String -> (a->b->c->d) -> [a]->[b]->[c]->[d]
zipWith4Equal :: String -> (a->b->c->d->e) -> [a]->[b]->[c]->[d]->[e]
#if !defined(DEBUG)
zipEqual _ = zip
zipWithEqual _ = zipWith
zipWith3Equal _ = zipWith3
zipWith4Equal _ = List.zipWith4
#else
zipEqual _ [] [] = []
zipEqual msg (a:as) (b:bs) = (a,b) : zipEqual msg as bs
zipEqual msg _ _ = panic ("zipEqual: unequal lists: "++msg)
zipWithEqual msg z (a:as) (b:bs)= z a b : zipWithEqual msg z as bs
zipWithEqual _ _ [] [] = []
zipWithEqual msg _ _ _ = panic ("zipWithEqual: unequal lists: "++msg)
zipWith3Equal msg z (a:as) (b:bs) (c:cs)
= z a b c : zipWith3Equal msg z as bs cs
zipWith3Equal _ _ [] [] [] = []
zipWith3Equal msg _ _ _ _ = panic ("zipWith3Equal: unequal lists: "++msg)
zipWith4Equal msg z (a:as) (b:bs) (c:cs) (d:ds)
= z a b c d : zipWith4Equal msg z as bs cs ds
zipWith4Equal _ _ [] [] [] [] = []
zipWith4Equal msg _ _ _ _ _ = panic ("zipWith4Equal: unequal lists: "++msg)
#endif
-- | 'zipLazy' is a kind of 'zip' that is lazy in the second list (observe the ~)
zipLazy :: [a] -> [b] -> [(a,b)]
zipLazy [] _ = []
zipLazy (x:xs) ~(y:ys) = (x,y) : zipLazy xs ys
-- | 'zipWithLazy' is like 'zipWith' but is lazy in the second list.
-- The length of the output is always the same as the length of the first
-- list.
zipWithLazy :: (a -> b -> c) -> [a] -> [b] -> [c]
zipWithLazy _ [] _ = []
zipWithLazy f (a:as) ~(b:bs) = f a b : zipWithLazy f as bs
-- | 'zipWith3Lazy' is like 'zipWith3' but is lazy in the second and third lists.
-- The length of the output is always the same as the length of the first
-- list.
zipWith3Lazy :: (a -> b -> c -> d) -> [a] -> [b] -> [c] -> [d]
zipWith3Lazy _ [] _ _ = []
zipWith3Lazy f (a:as) ~(b:bs) ~(c:cs) = f a b c : zipWith3Lazy f as bs cs
-- | 'filterByList' takes a list of Bools and a list of some elements and
-- filters out these elements for which the corresponding value in the list of
-- Bools is False. This function does not check whether the lists have equal
-- length.
filterByList :: [Bool] -> [a] -> [a]
filterByList (True:bs) (x:xs) = x : filterByList bs xs
filterByList (False:bs) (_:xs) = filterByList bs xs
filterByList _ _ = []
-- | 'filterByLists' takes a list of Bools and two lists as input, and
-- outputs a new list consisting of elements from the last two input lists. For
-- each Bool in the list, if it is 'True', then it takes an element from the
-- former list. If it is 'False', it takes an element from the latter list.
-- The elements taken correspond to the index of the Bool in its list.
-- For example:
--
-- @
-- filterByLists [True, False, True, False] \"abcd\" \"wxyz\" = \"axcz\"
-- @
--
-- This function does not check whether the lists have equal length.
filterByLists :: [Bool] -> [a] -> [a] -> [a]
filterByLists (True:bs) (x:xs) (_:ys) = x : filterByLists bs xs ys
filterByLists (False:bs) (_:xs) (y:ys) = y : filterByLists bs xs ys
filterByLists _ _ _ = []
-- | 'partitionByList' takes a list of Bools and a list of some elements and
-- partitions the list according to the list of Bools. Elements corresponding
-- to 'True' go to the left; elements corresponding to 'False' go to the right.
-- For example, @partitionByList [True, False, True] [1,2,3] == ([1,3], [2])@
-- This function does not check whether the lists have equal
-- length; when one list runs out, the function stops.
partitionByList :: [Bool] -> [a] -> ([a], [a])
partitionByList = go [] []
where
go trues falses (True : bs) (x : xs) = go (x:trues) falses bs xs
go trues falses (False : bs) (x : xs) = go trues (x:falses) bs xs
go trues falses _ _ = (reverse trues, reverse falses)
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@
stretchZipWith _ _ _ [] _ = []
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
mapFst :: (a->c) -> [(a,b)] -> [(c,b)]
mapSnd :: (b->c) -> [(a,b)] -> [(a,c)]
mapFst f xys = [(f x, y) | (x,y) <- xys]
mapSnd f xys = [(x, f y) | (x,y) <- xys]
mapAndUnzip :: (a -> (b, c)) -> [a] -> ([b], [c])
mapAndUnzip _ [] = ([], [])
mapAndUnzip f (x:xs)
= let (r1, r2) = f x
(rs1, rs2) = mapAndUnzip f xs
in
(r1:rs1, r2:rs2)
mapAndUnzip3 :: (a -> (b, c, d)) -> [a] -> ([b], [c], [d])
mapAndUnzip3 _ [] = ([], [], [])
mapAndUnzip3 f (x:xs)
= let (r1, r2, r3) = f x
(rs1, rs2, rs3) = mapAndUnzip3 f xs
in
(r1:rs1, r2:rs2, r3:rs3)
zipWithAndUnzip :: (a -> b -> (c,d)) -> [a] -> [b] -> ([c],[d])
zipWithAndUnzip f (a:as) (b:bs)
= let (r1, r2) = f a b
(rs1, rs2) = zipWithAndUnzip f as bs
in
(r1:rs1, r2:rs2)
zipWithAndUnzip _ _ _ = ([],[])
-- | This has the effect of making the two lists have equal length by dropping
-- the tail of the longer one.
zipAndUnzip :: [a] -> [b] -> ([a],[b])
zipAndUnzip (a:as) (b:bs)
= let (rs1, rs2) = zipAndUnzip as bs
in
(a:rs1, b:rs2)
zipAndUnzip _ _ = ([],[])
-- | @atLength atLen atEnd ls n@ unravels list @ls@ to position @n@. Precisely:
--
-- @
-- atLength atLenPred atEndPred ls n
-- | n < 0 = atLenPred ls
-- | length ls < n = atEndPred (n - length ls)
-- | otherwise = atLenPred (drop n ls)
-- @
atLength :: ([a] -> b) -- Called when length ls >= n, passed (drop n ls)
-- NB: arg passed to this function may be []
-> b -- Called when length ls < n
-> [a]
-> Int
-> b
atLength atLenPred atEnd ls0 n0
| n0 < 0 = atLenPred ls0
| otherwise = go n0 ls0
where
-- go's first arg n >= 0
go 0 ls = atLenPred ls
go _ [] = atEnd -- n > 0 here
go n (_:xs) = go (n-1) xs
-- Some special cases of atLength:
-- | @(lengthExceeds xs n) = (length xs > n)@
lengthExceeds :: [a] -> Int -> Bool
lengthExceeds lst n
| n < 0
= True
| otherwise
= atLength notNull False lst n
-- | @(lengthAtLeast xs n) = (length xs >= n)@
lengthAtLeast :: [a] -> Int -> Bool
lengthAtLeast = atLength (const True) False
-- | @(lengthIs xs n) = (length xs == n)@
lengthIs :: [a] -> Int -> Bool
lengthIs lst n
| n < 0
= False
| otherwise
= atLength null False lst n
-- | @(lengthIsNot xs n) = (length xs /= n)@
lengthIsNot :: [a] -> Int -> Bool
lengthIsNot lst n
| n < 0 = True
| otherwise = atLength notNull True lst n
-- | @(lengthAtMost xs n) = (length xs <= n)@
lengthAtMost :: [a] -> Int -> Bool
lengthAtMost lst n
| n < 0
= False
| otherwise
= atLength null True lst n
-- | @(lengthLessThan xs n) == (length xs < n)@
lengthLessThan :: [a] -> Int -> Bool
lengthLessThan = atLength (const False) True
listLengthCmp :: [a] -> Int -> Ordering
listLengthCmp = atLength atLen atEnd
where
atEnd = LT -- Not yet seen 'n' elts, so list length is < n.
atLen [] = EQ
atLen _ = GT
equalLength :: [a] -> [b] -> Bool
-- ^ True if length xs == length ys
equalLength [] [] = True
equalLength (_:xs) (_:ys) = equalLength xs ys
equalLength _ _ = False
compareLength :: [a] -> [b] -> Ordering
compareLength [] [] = EQ
compareLength (_:xs) (_:ys) = compareLength xs ys
compareLength [] _ = LT
compareLength _ [] = GT
leLength :: [a] -> [b] -> Bool
-- ^ True if length xs <= length ys
leLength xs ys = case compareLength xs ys of
LT -> True
EQ -> True
GT -> False
ltLength :: [a] -> [b] -> Bool
-- ^ True if length xs < length ys
ltLength xs ys = case compareLength xs ys of
LT -> True
EQ -> False
GT -> False
----------------------------
singleton :: a -> [a]
singleton x = [x]
isSingleton :: [a] -> Bool
isSingleton [_] = True
isSingleton _ = False
notNull :: Foldable f => f a -> Bool
notNull = not . null
only :: [a] -> a
#if defined(DEBUG)
only [a] = a
#else
only (a:_) = a
#endif
only _ = panic "Util: only"
-- Debugging/specialising versions of \tr{elem} and \tr{notElem}
# if !defined(DEBUG)
isIn, isn'tIn :: Eq a => String -> a -> [a] -> Bool
isIn _msg x ys = x `elem` ys
isn'tIn _msg x ys = x `notElem` ys
# else /* DEBUG */
isIn, isn'tIn :: (HasDebugCallStack, Eq a) => String -> a -> [a] -> Bool
isIn msg x ys
= elem100 0 x ys
where
elem100 :: Eq a => Int -> a -> [a] -> Bool
elem100 _ _ [] = False
elem100 i x (y:ys)
| i > 100 = WARN(True, text ("Over-long elem in " ++ msg)) (x `elem` (y:ys))
| otherwise = x == y || elem100 (i + 1) x ys
isn'tIn msg x ys
= notElem100 0 x ys
where
notElem100 :: Eq a => Int -> a -> [a] -> Bool
notElem100 _ _ [] = True
notElem100 i x (y:ys)
| i > 100 = WARN(True, text ("Over-long notElem in " ++ msg)) (x `notElem` (y:ys))
| otherwise = x /= y && notElem100 (i + 1) x ys
# endif /* DEBUG */
-- | Split a list into chunks of /n/ elements
chunkList :: Int -> [a] -> [[a]]
chunkList _ [] = []
chunkList n xs = as : chunkList n bs where (as,bs) = splitAt n xs
-- | Replace the last element of a list with another element.
changeLast :: [a] -> a -> [a]
changeLast [] _ = panic "changeLast"
changeLast [_] x = [x]
changeLast (x:xs) x' = x : changeLast xs x'
-- | Apply an effectful function to the last list element.
-- Assumes a non-empty list (panics otherwise).
mapLastM :: Functor f => (a -> f a) -> [a] -> f [a]
mapLastM _ [] = panic "mapLastM: empty list"
mapLastM f [x] = (\x' -> [x']) <$> f x
mapLastM f (x:xs) = (x:) <$> mapLastM f xs
whenNonEmpty :: Applicative m => [a] -> (NonEmpty a -> m ()) -> m ()
whenNonEmpty [] _ = pure ()
whenNonEmpty (x:xs) f = f (x :| xs)
-- | Merge an unsorted list of sorted lists, for example:
--
-- > mergeListsBy compare [ [2,5,15], [1,10,100] ] = [1,2,5,10,15,100]
--
-- \( O(n \log{} k) \)
mergeListsBy :: forall a. (a -> a -> Ordering) -> [[a]] -> [a]
mergeListsBy cmp lists | debugIsOn, not (all sorted lists) =
-- When debugging is on, we check that the input lists are sorted.
panic "mergeListsBy: input lists must be sorted"
where sorted = isSortedBy cmp
mergeListsBy cmp all_lists = merge_lists all_lists
where
-- Implements "Iterative 2-Way merge" described at
-- https://en.wikipedia.org/wiki/K-way_merge_algorithm
-- Merge two sorted lists into one in O(n).
merge2 :: [a] -> [a] -> [a]
merge2 [] ys = ys
merge2 xs [] = xs
merge2 (x:xs) (y:ys) =
case cmp x y of
GT -> y : merge2 (x:xs) ys
_ -> x : merge2 xs (y:ys)
-- Merge the first list with the second, the third with the fourth, and so
-- on. The output has half as much lists as the input.
merge_neighbours :: [[a]] -> [[a]]
merge_neighbours [] = []
merge_neighbours [xs] = [xs]
merge_neighbours (xs : ys : lists) =
merge2 xs ys : merge_neighbours lists
-- Since 'merge_neighbours' halves the amount of lists in each iteration,
-- we perform O(log k) iteration. Each iteration is O(n). The total running
-- time is therefore O(n log k).
merge_lists :: [[a]] -> [a]
merge_lists lists =
case merge_neighbours lists of
[] -> []
[xs] -> xs
lists' -> merge_lists lists'
isSortedBy :: (a -> a -> Ordering) -> [a] -> Bool
isSortedBy cmp = sorted
where
sorted [] = True
sorted [_] = True
sorted (x:y:xs) = cmp x y /= GT && sorted (y:xs)
{-
************************************************************************
* *
\subsubsection{Sort utils}
* *
************************************************************************
-}
minWith :: Ord b => (a -> b) -> [a] -> a
minWith get_key xs = ASSERT( not (null xs) )
head (sortWith get_key xs)
nubSort :: Ord a => [a] -> [a]
nubSort = Set.toAscList . Set.fromList
-- | Remove duplicates but keep elements in order.
-- O(n * log n)
ordNub :: Ord a => [a] -> [a]
ordNub xs
= go Set.empty xs
where
go _ [] = []
go s (x:xs)
| Set.member x s = go s xs
| otherwise = x : go (Set.insert x s) xs
{-
************************************************************************
* *
\subsection[Utils-transitive-closure]{Transitive closure}
* *
************************************************************************
This algorithm for transitive closure is straightforward, albeit quadratic.
-}
transitiveClosure :: (a -> [a]) -- Successor function
-> (a -> a -> Bool) -- Equality predicate
-> [a]
-> [a] -- The transitive closure
transitiveClosure succ eq xs
= go [] xs
where
go done [] = done
go done (x:xs) | x `is_in` done = go done xs
| otherwise = go (x:done) (succ x ++ xs)
_ `is_in` [] = False
x `is_in` (y:ys) | eq x y = True
| otherwise = x `is_in` ys
{-
************************************************************************
* *
\subsection[Utils-accum]{Accumulating}
* *
************************************************************************
A combination of foldl with zip. It works with equal length lists.
-}
foldl2 :: (acc -> a -> b -> acc) -> acc -> [a] -> [b] -> acc
foldl2 _ z [] [] = z
foldl2 k z (a:as) (b:bs) = foldl2 k (k z a b) as bs
foldl2 _ _ _ _ = panic "Util: foldl2"
all2 :: (a -> b -> Bool) -> [a] -> [b] -> Bool
-- True if the lists are the same length, and
-- all corresponding elements satisfy the predicate
all2 _ [] [] = True
all2 p (x:xs) (y:ys) = p x y && all2 p xs ys
all2 _ _ _ = False
-- Count the number of times a predicate is true
count :: (a -> Bool) -> [a] -> Int
count p = go 0
where go !n [] = n
go !n (x:xs) | p x = go (n+1) xs
| otherwise = go n xs
countWhile :: (a -> Bool) -> [a] -> Int
-- Length of an /initial prefix/ of the list satisfying p
countWhile p = go 0
where go !n (x:xs) | p x = go (n+1) xs
go !n _ = n
{-
@splitAt@, @take@, and @drop@ but with length of another
list giving the break-off point:
-}
takeList :: [b] -> [a] -> [a]
-- (takeList as bs) trims bs to the be same length
-- as as, unless as is longer in which case it's a no-op
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
-- | Given two lists xs and ys, return `splitAt (length xs) ys`.
splitAtList :: [b] -> [a] -> ([a], [a])
splitAtList xs ys = go 0# xs ys
where
-- we are careful to avoid allocating when there are no leftover
-- arguments: in this case we can return "ys" directly (cf #18535)
--
-- We make `xs` strict because in the general case `ys` isn't `[]` so we
-- will have to evaluate `xs` anyway.
go _ !_ [] = (ys, []) -- length ys <= length xs
go n [] bs = (take (I# n) ys, bs) -- = splitAt n ys
go n (_:as) (_:bs) = go (n +# 1#) as bs
-- drop from the end of a list
dropTail :: Int -> [a] -> [a]
-- Specification: dropTail n = reverse . drop n . reverse
-- Better implementation due to Joachim Breitner
-- http://www.joachim-breitner.de/blog/archives/600-On-taking-the-last-n-elements-of-a-list.html
dropTail n xs
= go (drop n xs) xs
where
go (_:ys) (x:xs) = x : go ys xs
go _ _ = [] -- Stop when ys runs out
-- It'll always run out before xs does
-- dropWhile from the end of a list. This is similar to Data.List.dropWhileEnd,
-- but is lazy in the elements and strict in the spine. For reasonably short lists,
-- such as path names and typical lines of text, dropWhileEndLE is generally
-- faster than dropWhileEnd. Its advantage is magnified when the predicate is
-- expensive--using dropWhileEndLE isSpace to strip the space off a line of text
-- is generally much faster than using dropWhileEnd isSpace for that purpose.
-- Specification: dropWhileEndLE p = reverse . dropWhile p . reverse
-- Pay attention to the short-circuit (&&)! The order of its arguments is the only
-- difference between dropWhileEnd and dropWhileEndLE.
dropWhileEndLE :: (a -> Bool) -> [a] -> [a]
dropWhileEndLE p = foldr (\x r -> if null r && p x then [] else x:r) []
-- | @spanEnd p l == reverse (span p (reverse l))@. The first list
-- returns actually comes after the second list (when you look at the
-- input list).
spanEnd :: (a -> Bool) -> [a] -> ([a], [a])
spanEnd p l = go l [] [] l
where go yes _rev_yes rev_no [] = (yes, reverse rev_no)
go yes rev_yes rev_no (x:xs)
| p x = go yes (x : rev_yes) rev_no xs
| otherwise = go xs [] (x : rev_yes ++ rev_no) xs
-- | Get the last two elements in a list. Partial!
{-# INLINE last2 #-}
last2 :: [a] -> (a,a)
last2 = List.foldl' (\(_,x2) x -> (x2,x)) (partialError,partialError)
where
partialError = panic "last2 - list length less than two"
lastMaybe :: [a] -> Maybe a
lastMaybe [] = Nothing
lastMaybe xs = Just $ last xs
-- | Split a list into its last element and the initial part of the list.
-- @snocView xs = Just (init xs, last xs)@ for non-empty lists.
-- @snocView xs = Nothing@ otherwise.
-- Unless both parts of the result are guaranteed to be used
-- prefer separate calls to @last@ + @init@.
-- If you are guaranteed to use both, this will
-- be more efficient.
snocView :: [a] -> Maybe ([a],a)
snocView [] = Nothing
snocView xs
| (xs,x) <- go xs
= Just (xs,x)
where
go :: [a] -> ([a],a)
go [x] = ([],x)
go (x:xs)
| !(xs',x') <- go xs
= (x:xs', x')
go [] = error "impossible"
split :: Char -> String -> [String]
split c s = case rest of
[] -> [chunk]
_:rest -> chunk : split c rest
where (chunk, rest) = break (==c) s
-- | Convert a word to title case by capitalising the first letter
capitalise :: String -> String
capitalise [] = []
capitalise (c:cs) = toUpper c : cs
{-
************************************************************************
* *
\subsection[Utils-comparison]{Comparisons}
* *
************************************************************************
-}
isEqual :: Ordering -> Bool
-- Often used in (isEqual (a `compare` b))
isEqual GT = False
isEqual EQ = True
isEqual LT = False
thenCmp :: Ordering -> Ordering -> Ordering
{-# INLINE thenCmp #-}
thenCmp EQ ordering = ordering
thenCmp ordering _ = ordering
eqListBy :: (a->a->Bool) -> [a] -> [a] -> Bool
eqListBy _ [] [] = True
eqListBy eq (x:xs) (y:ys) = eq x y && eqListBy eq xs ys
eqListBy _ _ _ = False
eqMaybeBy :: (a ->a->Bool) -> Maybe a -> Maybe a -> Bool
eqMaybeBy _ Nothing Nothing = True
eqMaybeBy eq (Just x) (Just y) = eq x y
eqMaybeBy _ _ _ = False
cmpList :: (a -> a -> Ordering) -> [a] -> [a] -> Ordering
-- `cmpList' uses a user-specified comparer
cmpList _ [] [] = EQ
cmpList _ [] _ = LT
cmpList _ _ [] = GT
cmpList cmp (a:as) (b:bs)
= case cmp a b of { EQ -> cmpList cmp as bs; xxx -> xxx }
removeSpaces :: String -> String
removeSpaces = dropWhileEndLE isSpace . dropWhile isSpace
-- Boolean operators lifted to Applicative
(<&&>) :: Applicative f => f Bool -> f Bool -> f Bool
(<&&>) = liftA2 (&&)
infixr 3 <&&> -- same as (&&)
(<||>) :: Applicative f => f Bool -> f Bool -> f Bool
(<||>) = liftA2 (||)
infixr 2 <||> -- same as (||)
{-
************************************************************************
* *
\subsection{Edit distance}
* *
************************************************************************
-}
-- | Find the "restricted" Damerau-Levenshtein edit distance between two strings.
-- See: .
-- Based on the algorithm presented in "A Bit-Vector Algorithm for Computing
-- Levenshtein and Damerau Edit Distances" in PSC'02 (Heikki Hyyro).
-- See http://www.cs.uta.fi/~helmu/pubs/psc02.pdf and
-- http://www.cs.uta.fi/~helmu/pubs/PSCerr.html for an explanation
restrictedDamerauLevenshteinDistance :: String -> String -> Int
restrictedDamerauLevenshteinDistance str1 str2
= restrictedDamerauLevenshteinDistanceWithLengths m n str1 str2
where
m = length str1
n = length str2
restrictedDamerauLevenshteinDistanceWithLengths
:: Int -> Int -> String -> String -> Int
restrictedDamerauLevenshteinDistanceWithLengths m n str1 str2
| m <= n
= if n <= 32 -- n must be larger so this check is sufficient
then restrictedDamerauLevenshteinDistance' (undefined :: Word32) m n str1 str2
else restrictedDamerauLevenshteinDistance' (undefined :: Integer) m n str1 str2
| otherwise
= if m <= 32 -- m must be larger so this check is sufficient
then restrictedDamerauLevenshteinDistance' (undefined :: Word32) n m str2 str1
else restrictedDamerauLevenshteinDistance' (undefined :: Integer) n m str2 str1
restrictedDamerauLevenshteinDistance'
:: (Bits bv, Num bv) => bv -> Int -> Int -> String -> String -> Int
restrictedDamerauLevenshteinDistance' _bv_dummy m n str1 str2
| [] <- str1 = n
| otherwise = extractAnswer $
List.foldl' (restrictedDamerauLevenshteinDistanceWorker
(matchVectors str1) top_bit_mask vector_mask)
(0, 0, m_ones, 0, m) str2
where
m_ones@vector_mask = (2 ^ m) - 1
top_bit_mask = (1 `shiftL` (m - 1)) `asTypeOf` _bv_dummy
extractAnswer (_, _, _, _, distance) = distance
restrictedDamerauLevenshteinDistanceWorker
:: (Bits bv, Num bv) => IM.IntMap bv -> bv -> bv
-> (bv, bv, bv, bv, Int) -> Char -> (bv, bv, bv, bv, Int)
restrictedDamerauLevenshteinDistanceWorker str1_mvs top_bit_mask vector_mask
(pm, d0, vp, vn, distance) char2
= seq str1_mvs $ seq top_bit_mask $ seq vector_mask $
seq pm' $ seq d0' $ seq vp' $ seq vn' $
seq distance'' $ seq char2 $
(pm', d0', vp', vn', distance'')
where
pm' = IM.findWithDefault 0 (ord char2) str1_mvs
d0' = ((((sizedComplement vector_mask d0) .&. pm') `shiftL` 1) .&. pm)
.|. ((((pm' .&. vp) + vp) .&. vector_mask) `xor` vp) .|. pm' .|. vn
-- No need to mask the shiftL because of the restricted range of pm
hp' = vn .|. sizedComplement vector_mask (d0' .|. vp)
hn' = d0' .&. vp
hp'_shift = ((hp' `shiftL` 1) .|. 1) .&. vector_mask
hn'_shift = (hn' `shiftL` 1) .&. vector_mask
vp' = hn'_shift .|. sizedComplement vector_mask (d0' .|. hp'_shift)
vn' = d0' .&. hp'_shift
distance' = if hp' .&. top_bit_mask /= 0 then distance + 1 else distance
distance'' = if hn' .&. top_bit_mask /= 0 then distance' - 1 else distance'
sizedComplement :: Bits bv => bv -> bv -> bv
sizedComplement vector_mask vect = vector_mask `xor` vect
matchVectors :: (Bits bv, Num bv) => String -> IM.IntMap bv
matchVectors = snd . List.foldl' go (0 :: Int, IM.empty)
where
go (ix, im) char = let ix' = ix + 1
im' = IM.insertWith (.|.) (ord char) (2 ^ ix) im
in seq ix' $ seq im' $ (ix', im')
{-# SPECIALIZE INLINE restrictedDamerauLevenshteinDistance'
:: Word32 -> Int -> Int -> String -> String -> Int #-}
{-# SPECIALIZE INLINE restrictedDamerauLevenshteinDistance'
:: Integer -> Int -> Int -> String -> String -> Int #-}
{-# SPECIALIZE restrictedDamerauLevenshteinDistanceWorker
:: IM.IntMap Word32 -> Word32 -> Word32
-> (Word32, Word32, Word32, Word32, Int)
-> Char -> (Word32, Word32, Word32, Word32, Int) #-}
{-# SPECIALIZE restrictedDamerauLevenshteinDistanceWorker
:: IM.IntMap Integer -> Integer -> Integer
-> (Integer, Integer, Integer, Integer, Int)
-> Char -> (Integer, Integer, Integer, Integer, Int) #-}
{-# SPECIALIZE INLINE sizedComplement :: Word32 -> Word32 -> Word32 #-}
{-# SPECIALIZE INLINE sizedComplement :: Integer -> Integer -> Integer #-}
{-# SPECIALIZE matchVectors :: String -> IM.IntMap Word32 #-}
{-# SPECIALIZE matchVectors :: String -> IM.IntMap Integer #-}
fuzzyMatch :: String -> [String] -> [String]
fuzzyMatch key vals = fuzzyLookup key [(v,v) | v <- vals]
-- | Search for possible matches to the users input in the given list,
-- returning a small number of ranked results
fuzzyLookup :: String -> [(String,a)] -> [a]
fuzzyLookup user_entered possibilites
= map fst $ take mAX_RESULTS $ List.sortBy (comparing snd)
[ (poss_val, distance) | (poss_str, poss_val) <- possibilites
, let distance = restrictedDamerauLevenshteinDistance
poss_str user_entered
, distance <= fuzzy_threshold ]
where
-- Work out an appropriate match threshold:
-- We report a candidate if its edit distance is <= the threshold,
-- The threshold is set to about a quarter of the # of characters the user entered
-- Length Threshold
-- 1 0 -- Don't suggest *any* candidates
-- 2 1 -- for single-char identifiers
-- 3 1
-- 4 1
-- 5 1
-- 6 2
--
fuzzy_threshold = truncate $ fromIntegral (length user_entered + 2) / (4 :: Rational)
mAX_RESULTS = 3
{-
************************************************************************
* *
\subsection[Utils-pairs]{Pairs}
* *
************************************************************************
-}
unzipWith :: (a -> b -> c) -> [(a, b)] -> [c]
unzipWith f pairs = map ( \ (a, b) -> f a b ) pairs
seqList :: [a] -> b -> b
seqList [] b = b
seqList (x:xs) b = x `seq` seqList xs b
strictMap :: (a -> b) -> [a] -> [b]
strictMap _ [] = []
strictMap f (x : xs) =
let
!x' = f x
!xs' = strictMap f xs
in
x' : xs'
-- Module names:
looksLikeModuleName :: String -> Bool
looksLikeModuleName [] = False
looksLikeModuleName (c:cs) = isUpper c && go cs
where go [] = True
go ('.':cs) = looksLikeModuleName cs
go (c:cs) = (isAlphaNum c || c == '_' || c == '\'') && go cs
-- Similar to 'parse' for Distribution.Package.PackageName,
-- but we don't want to depend on Cabal.
looksLikePackageName :: String -> Bool
looksLikePackageName = all (all isAlphaNum <&&> not . (all isDigit)) . split '-'
{-
Akin to @Prelude.words@, but acts like the Bourne shell, treating
quoted strings as Haskell Strings, and also parses Haskell [String]
syntax.
-}
getCmd :: String -> Either String -- Error
(String, String) -- (Cmd, Rest)
getCmd s = case break isSpace $ dropWhile isSpace s of
([], _) -> Left ("Couldn't find command in " ++ show s)
res -> Right res
toCmdArgs :: String -> Either String -- Error
(String, [String]) -- (Cmd, Args)
toCmdArgs s = case getCmd s of
Left err -> Left err
Right (cmd, s') -> case toArgs s' of
Left err -> Left err
Right args -> Right (cmd, args)
toArgs :: String -> Either String -- Error
[String] -- Args
toArgs str
= case dropWhile isSpace str of
s@('[':_) -> case reads s of
[(args, spaces)]
| all isSpace spaces ->
Right args
_ ->
Left ("Couldn't read " ++ show str ++ " as [String]")
s -> toArgs' s
where
toArgs' :: String -> Either String [String]
-- Remove outer quotes:
-- > toArgs' "\"foo\" \"bar baz\""
-- Right ["foo", "bar baz"]
--
-- Keep inner quotes:
-- > toArgs' "-DFOO=\"bar baz\""
-- Right ["-DFOO=\"bar baz\""]
toArgs' s = case dropWhile isSpace s of
[] -> Right []
('"' : _) -> do
-- readAsString removes outer quotes
(arg, rest) <- readAsString s
(arg:) `fmap` toArgs' rest
s' -> case break (isSpace <||> (== '"')) s' of
(argPart1, s''@('"':_)) -> do
(argPart2, rest) <- readAsString s''
-- show argPart2 to keep inner quotes
((argPart1 ++ show argPart2):) `fmap` toArgs' rest
(arg, s'') -> (arg:) `fmap` toArgs' s''
readAsString :: String -> Either String (String, String)
readAsString s = case reads s of
[(arg, rest)]
-- rest must either be [] or start with a space
| all isSpace (take 1 rest) ->
Right (arg, rest)
_ ->
Left ("Couldn't read " ++ show s ++ " as String")
-----------------------------------------------------------------------------
-- Integers
-- | Determine the $\log_2$ of exact powers of 2
exactLog2 :: Integer -> Maybe Integer
exactLog2 x
| x <= 0 = Nothing
| x > fromIntegral (maxBound :: Int32) = Nothing
| x' .&. (-x') /= x' = Nothing
| otherwise = Just (fromIntegral c)
where
x' = fromIntegral x :: Int32
c = countTrailingZeros x'
{-
-- -----------------------------------------------------------------------------
-- Floats
-}
readRational__ :: ReadS Rational -- NB: doesn't handle leading "-"
readRational__ r = do
((i, e), t) <- readSignificandExponentPair__ r
return ((i%1)*10^^e, 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)
readSignificandExponentPair__ :: ReadS (Integer, Integer) -- NB: doesn't handle leading "-"
readSignificandExponentPair__ r = do
(n,d,s) <- readFix r
(k,t) <- readExp s
let pair = (n, toInteger (k - d))
return (pair, 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)
span' _ xs@[] = (xs, xs)
span' p xs@(x:xs')
| x == '_' = span' p xs' -- skip "_" (#14473)
| p x = let (ys,zs) = span' p xs' in (x:ys,zs)
| otherwise = ([],xs)
-- | Parse a string into a significand and exponent.
-- A trivial example might be:
-- ghci> readSignificandExponentPair "1E2"
-- (1,2)
-- In a more complex case we might return a exponent different than that
-- which the user wrote. This is needed in order to use a Integer significand.
-- ghci> readSignificandExponentPair "-1.11E5"
-- (-111,3)
readSignificandExponentPair :: String -> (Integer, Integer) -- NB: *does* handle a leading "-"
readSignificandExponentPair top_s
= case top_s of
'-' : xs -> let (i, e) = read_me xs in (-i, e)
xs -> read_me xs
where
read_me s
= case (do { (x,"") <- readSignificandExponentPair__ s ; return x }) of
[x] -> x
[] -> error ("readSignificandExponentPair: no parse:" ++ top_s)
_ -> error ("readSignificandExponentPair: ambiguous parse:" ++ top_s)
readHexRational :: String -> Rational
readHexRational str =
case str of
'-' : xs -> - (readMe xs)
xs -> readMe xs
where
readMe as =
case readHexRational__ as of
Just n -> n
_ -> error ("readHexRational: no parse:" ++ str)
readHexRational__ :: String -> Maybe Rational
readHexRational__ ('0' : x : rest)
| x == 'X' || x == 'x' =
do let (front,rest2) = span' isHexDigit rest
guard (not (null front))
let frontNum = steps 16 0 front
case rest2 of
'.' : rest3 ->
do let (back,rest4) = span' isHexDigit rest3
guard (not (null back))
let backNum = steps 16 frontNum back
exp1 = -4 * length back
case rest4 of
p : ps | isExp p -> fmap (mk backNum . (+ exp1)) (getExp ps)
_ -> return (mk backNum exp1)
p : ps | isExp p -> fmap (mk frontNum) (getExp ps)
_ -> Nothing
where
isExp p = p == 'p' || p == 'P'
getExp ('+' : ds) = dec ds
getExp ('-' : ds) = fmap negate (dec ds)
getExp ds = dec ds
mk :: Integer -> Int -> Rational
mk n e = fromInteger n * 2^^e
dec cs = case span' isDigit cs of
(ds,"") | not (null ds) -> Just (steps 10 0 ds)
_ -> Nothing
steps base n ds = List.foldl' (step base) n ds
step base n d = base * n + fromIntegral (digitToInt d)
span' _ xs@[] = (xs, xs)
span' p xs@(x:xs')
| x == '_' = span' p xs' -- skip "_" (#14473)
| p x = let (ys,zs) = span' p xs' in (x:ys,zs)
| otherwise = ([],xs)
readHexRational__ _ = Nothing
-- | Parse a string into a significand and exponent according to
-- the "Hexadecimal Floats in Haskell" proposal.
-- A trivial example might be:
-- ghci> readHexSignificandExponentPair "0x1p+1"
-- (1,1)
-- Behaves similar to readSignificandExponentPair but the base is 16
-- and numbers are given in hexadecimal:
-- ghci> readHexSignificandExponentPair "0xAp-4"
-- (10,-4)
-- ghci> readHexSignificandExponentPair "0x1.2p3"
-- (18,-1)
readHexSignificandExponentPair :: String -> (Integer, Integer)
readHexSignificandExponentPair str =
case str of
'-' : xs -> let (i, e) = readMe xs in (-i, e)
xs -> readMe xs
where
readMe as =
case readHexSignificandExponentPair__ as of
Just n -> n
_ -> error ("readHexSignificandExponentPair: no parse:" ++ str)
readHexSignificandExponentPair__ :: String -> Maybe (Integer, Integer)
readHexSignificandExponentPair__ ('0' : x : rest)
| x == 'X' || x == 'x' =
do let (front,rest2) = span' isHexDigit rest
guard (not (null front))
let frontNum = steps 16 0 front
case rest2 of
'.' : rest3 ->
do let (back,rest4) = span' isHexDigit rest3
guard (not (null back))
let backNum = steps 16 frontNum back
exp1 = -4 * length back
case rest4 of
p : ps | isExp p -> fmap (mk backNum . (+ exp1)) (getExp ps)
_ -> return (mk backNum exp1)
p : ps | isExp p -> fmap (mk frontNum) (getExp ps)
_ -> Nothing
where
isExp p = p == 'p' || p == 'P'
getExp ('+' : ds) = dec ds
getExp ('-' : ds) = fmap negate (dec ds)
getExp ds = dec ds
mk :: Integer -> Int -> (Integer, Integer)
mk n e = (n, fromIntegral e)
dec cs = case span' isDigit cs of
(ds,"") | not (null ds) -> Just (steps 10 0 ds)
_ -> Nothing
steps base n ds = foldl' (step base) n ds
step base n d = base * n + fromIntegral (digitToInt d)
span' _ xs@[] = (xs, xs)
span' p xs@(x:xs')
| x == '_' = span' p xs' -- skip "_" (#14473)
| p x = let (ys,zs) = span' p xs' in (x:ys,zs)
| otherwise = ([],xs)
readHexSignificandExponentPair__ _ = Nothing
-----------------------------------------------------------------------------
-- Verify that the 'dirname' portion of a FilePath exists.
--
doesDirNameExist :: FilePath -> IO Bool
doesDirNameExist fpath = doesDirectoryExist (takeDirectory fpath)
-----------------------------------------------------------------------------
-- Backwards compatibility definition of getModificationTime
getModificationUTCTime :: FilePath -> IO UTCTime
getModificationUTCTime = getModificationTime
-- --------------------------------------------------------------
-- check existence & modification time at the same time
modificationTimeIfExists :: FilePath -> IO (Maybe UTCTime)
modificationTimeIfExists f =
(do t <- getModificationUTCTime f; return (Just t))
`catchIO` \e -> if isDoesNotExistError e
then return Nothing
else ioError e
-- --------------------------------------------------------------
-- atomic file writing by writing to a temporary file first (see #14533)
--
-- This should be used in all cases where GHC writes files to disk
-- and uses their modification time to skip work later,
-- as otherwise a partially written file (e.g. due to crash or Ctrl+C)
-- also results in a skip.
withAtomicRename :: (MonadIO m) => FilePath -> (FilePath -> m a) -> m a
withAtomicRename targetFile f = do
-- The temp file must be on the same file system (mount) as the target file
-- to result in an atomic move on most platforms.
-- The standard way to ensure that is to place it into the same directory.
-- This can still be fooled when somebody mounts a different file system
-- at just the right time, but that is not a case we aim to cover here.
let temp = targetFile <.> "tmp"
res <- f temp
liftIO $ renameFile temp targetFile
return res
-- --------------------------------------------------------------
-- split a string at the last character where 'pred' is True,
-- returning a pair of strings. The first component holds the string
-- up (but not including) the last character for which 'pred' returned
-- True, the second whatever comes after (but also not including the
-- last character).
--
-- If 'pred' returns False for all characters in the string, the original
-- string is returned in the first component (and the second one is just
-- empty).
splitLongestPrefix :: String -> (Char -> Bool) -> (String,String)
splitLongestPrefix str pred
| null r_pre = (str, [])
| otherwise = (reverse (tail r_pre), reverse r_suf)
-- 'tail' drops the char satisfying 'pred'
where (r_suf, r_pre) = break pred (reverse str)
escapeSpaces :: String -> String
escapeSpaces = foldr (\c s -> if isSpace c then '\\':c:s else c:s) ""
type Suffix = String
--------------------------------------------------------------
-- * Search path
--------------------------------------------------------------
data Direction = Forwards | Backwards
reslash :: Direction -> FilePath -> FilePath
reslash d = f
where f ('/' : xs) = slash : f xs
f ('\\' : xs) = slash : f xs
f (x : xs) = x : f xs
f "" = ""
slash = case d of
Forwards -> '/'
Backwards -> '\\'
makeRelativeTo :: FilePath -> FilePath -> FilePath
this `makeRelativeTo` that = directory thisFilename
where (thisDirectory, thisFilename) = splitFileName this
thatDirectory = dropFileName that
directory = joinPath $ f (splitPath thisDirectory)
(splitPath thatDirectory)
f (x : xs) (y : ys)
| x == y = f xs ys
f xs ys = replicate (length ys) ".." ++ xs
{-
************************************************************************
* *
\subsection[Utils-Data]{Utils for defining Data instances}
* *
************************************************************************
These functions helps us to define Data instances for abstract types.
-}
abstractConstr :: String -> Constr
abstractConstr n = mkConstr (abstractDataType n) ("{abstract:"++n++"}") [] Prefix
abstractDataType :: String -> DataType
abstractDataType n = mkDataType n [abstractConstr n]
{-
************************************************************************
* *
\subsection[Utils-C]{Utils for printing C code}
* *
************************************************************************
-}
charToC :: Word8 -> String
charToC w =
case chr (fromIntegral w) of
'\"' -> "\\\""
'\'' -> "\\\'"
'\\' -> "\\\\"
c | c >= ' ' && c <= '~' -> [c]
| otherwise -> ['\\',
chr (ord '0' + ord c `div` 64),
chr (ord '0' + ord c `div` 8 `mod` 8),
chr (ord '0' + ord c `mod` 8)]
{-
************************************************************************
* *
\subsection[Utils-Hashing]{Utils for hashing}
* *
************************************************************************
-}
-- | A sample hash function for Strings. We keep multiplying by the
-- golden ratio and adding. The implementation is:
--
-- > hashString = foldl' f golden
-- > where f m c = fromIntegral (ord c) * magic + hashInt32 m
-- > magic = 0xdeadbeef
--
-- Where hashInt32 works just as hashInt shown above.
--
-- Knuth argues that repeated multiplication by the golden ratio
-- will minimize gaps in the hash space, and thus it's a good choice
-- for combining together multiple keys to form one.
--
-- Here we know that individual characters c are often small, and this
-- produces frequent collisions if we use ord c alone. A
-- particular problem are the shorter low ASCII and ISO-8859-1
-- character strings. We pre-multiply by a magic twiddle factor to
-- obtain a good distribution. In fact, given the following test:
--
-- > testp :: Int32 -> Int
-- > testp k = (n - ) . length . group . sort . map hs . take n $ ls
-- > where ls = [] : [c : l | l <- ls, c <- ['\0'..'\xff']]
-- > hs = foldl' f golden
-- > f m c = fromIntegral (ord c) * k + hashInt32 m
-- > n = 100000
--
-- We discover that testp magic = 0.
hashString :: String -> Int32
hashString = foldl' f golden
where f m c = fromIntegral (ord c) * magic + hashInt32 m
magic = fromIntegral (0xdeadbeef :: Word32)
golden :: Int32
golden = 1013904242 -- = round ((sqrt 5 - 1) * 2^32) :: Int32
-- was -1640531527 = round ((sqrt 5 - 1) * 2^31) :: Int32
-- but that has bad mulHi properties (even adding 2^32 to get its inverse)
-- Whereas the above works well and contains no hash duplications for
-- [-32767..65536]
-- | A sample (and useful) hash function for Int32,
-- implemented by extracting the uppermost 32 bits of the 64-bit
-- result of multiplying by a 33-bit constant. The constant is from
-- Knuth, derived from the golden ratio:
--
-- > golden = round ((sqrt 5 - 1) * 2^32)
--
-- We get good key uniqueness on small inputs
-- (a problem with previous versions):
-- (length $ group $ sort $ map hashInt32 [-32767..65536]) == 65536 + 32768
--
hashInt32 :: Int32 -> Int32
hashInt32 x = mulHi x golden + x
-- hi 32 bits of a x-bit * 32 bit -> 64-bit multiply
mulHi :: Int32 -> Int32 -> Int32
mulHi a b = fromIntegral (r `shiftR` 32)
where r :: Int64
r = fromIntegral a * fromIntegral b
-- | A call stack constraint, but only when 'isDebugOn'.
#if defined(DEBUG)
type HasDebugCallStack = HasCallStack
#else
type HasDebugCallStack = (() :: Constraint)
#endif
data OverridingBool
= Auto
| Always
| Never
deriving Show
overrideWith :: Bool -> OverridingBool -> Bool
overrideWith b Auto = b
overrideWith _ Always = True
overrideWith _ Never = False