ghc-7.10.0.20141222: The GHC API

Safe HaskellNone
LanguageHaskell2010

Util

Contents

Description

Highly random utility functions

Synopsis

Flags dependent on the compiler build

General list processing

zipEqual :: String -> [a] -> [b] -> [(a, b)] Source

zipWithEqual :: String -> (a -> b -> c) -> [a] -> [b] -> [c] Source

zipWith3Equal :: String -> (a -> b -> c -> d) -> [a] -> [b] -> [c] -> [d] Source

zipWith4Equal :: String -> (a -> b -> c -> d -> e) -> [a] -> [b] -> [c] -> [d] -> [e] Source

zipLazy :: [a] -> [b] -> [(a, b)] Source

zipLazy is a kind of zip that is lazy in the second list (observe the ~)

stretchZipWith :: (a -> Bool) -> b -> (a -> b -> c) -> [a] -> [b] -> [c] Source

stretchZipWith p z f xs ys stretches ys by inserting z in the places where p returns True

zipWithAndUnzip :: (a -> b -> (c, d)) -> [a] -> [b] -> ([c], [d]) Source

filterByList :: [Bool] -> [a] -> [a] Source

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.

unzipWith :: (a -> b -> c) -> [(a, b)] -> [c] Source

mapFst :: (a -> c) -> [(a, b)] -> [(c, b)] Source

mapSnd :: (b -> c) -> [(a, b)] -> [(a, c)] Source

chkAppend :: [a] -> [a] -> [a] Source

mapAndUnzip :: (a -> (b, c)) -> [a] -> ([b], [c]) Source

mapAndUnzip3 :: (a -> (b, c, d)) -> [a] -> ([b], [c], [d]) Source

mapAccumL2 :: (s1 -> s2 -> a -> (s1, s2, b)) -> s1 -> s2 -> [a] -> (s1, s2, [b]) Source

nOfThem :: Int -> a -> [a] Source

filterOut :: (a -> Bool) -> [a] -> [a] Source

Like filter, only it reverses the sense of the test

partitionWith :: (a -> Either b c) -> [a] -> ([b], [c]) Source

Uses a function to determine which of two output lists an input element should join

splitEithers :: [Either a b] -> ([a], [b]) Source

Teases a list of Eithers apart into two lists

dropWhileEndLE :: (a -> Bool) -> [a] -> [a] Source

foldl1' :: (a -> a -> a) -> [a] -> a Source

A strict version of foldl1

foldl2 :: (acc -> a -> b -> acc) -> acc -> [a] -> [b] -> acc Source

count :: (a -> Bool) -> [a] -> Int Source

all2 :: (a -> b -> Bool) -> [a] -> [b] -> Bool Source

lengthExceeds :: [a] -> Int -> Bool Source

(lengthExceeds xs n) = (length xs > n)

lengthIs :: [a] -> Int -> Bool Source

atLength :: ([a] -> b) -> (Int -> b) -> [a] -> Int -> b Source

atLength atLen atEnd ls n unravels list ls to position n. Precisely:

 atLength atLenPred atEndPred ls n
  | n < 0         = atLenPred n
  | length ls < n = atEndPred (n - length ls)
  | otherwise     = atLenPred (drop n ls)

equalLength :: [a] -> [b] -> Bool Source

compareLength :: [a] -> [b] -> Ordering Source

leLength :: [a] -> [b] -> Bool Source

True if length xs <= length ys

only :: [a] -> a Source

singleton :: a -> [a] Source

notNull :: [a] -> Bool Source

snocView :: [a] -> Maybe ([a], a) Source

isIn :: Eq a => String -> a -> [a] -> Bool Source

isn'tIn :: Eq a => String -> a -> [a] -> Bool Source

Tuples

fstOf3 :: (a, b, c) -> a Source

sndOf3 :: (a, b, c) -> b Source

thirdOf3 :: (a, b, c) -> c Source

firstM :: Monad m => (a -> m c) -> (a, b) -> m (c, b) Source

first3M :: Monad m => (a -> m d) -> (a, b, c) -> m (d, b, c) Source

third3 :: (c -> d) -> (a, b, c) -> (a, b, d) Source

uncurry3 :: (a -> b -> c -> d) -> (a, b, c) -> d Source

List operations controlled by another list

takeList :: [b] -> [a] -> [a] Source

dropList :: [b] -> [a] -> [a] Source

splitAtList :: [b] -> [a] -> ([a], [a]) Source

dropTail :: Int -> [a] -> [a] Source

For loop

nTimes :: Int -> (a -> a) -> a -> a Source

Compose a function with itself n times. (nth rather than twice)

Sorting

sortWith :: Ord b => (a -> b) -> [a] -> [a] Source

minWith :: Ord b => (a -> b) -> [a] -> a Source

nubSort :: Ord a => [a] -> [a] Source

Comparisons

eqListBy :: (a -> a -> Bool) -> [a] -> [a] -> Bool Source

eqMaybeBy :: (a -> a -> Bool) -> Maybe a -> Maybe a -> Bool Source

cmpList :: (a -> a -> Ordering) -> [a] -> [a] -> Ordering Source

Edit distance

fuzzyLookup :: String -> [(String, a)] -> [a] Source

Search for possible matches to the users input in the given list, returning a small number of ranked results

Transitive closures

transitiveClosure :: (a -> [a]) -> (a -> a -> Bool) -> [a] -> [a] Source

Strictness

seqList :: [a] -> b -> b Source

Module names

Argument processing

Floating point

read helpers

IO-ish utilities

global :: a -> IORef a Source

consIORef :: IORef [a] -> a -> IO () Source

Filenames and paths

data Direction Source

Constructors

Forwards 
Backwards 

Utils for defining Data instances

mkNoRepType :: String -> DataType Source

Constructs a non-representation for a non-representable type

Utils for printing C code

Hashing

hashString :: String -> Int32 Source

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.