License | GPL-3.0-or-later |
---|---|
Safe Haskell | None |
Language | Haskell2010 |
Copyright: Oleg Grenrus
Fat-prelude.
Synopsis
- (&&&) :: Arrow a => a b c -> a b c' -> a b (c, c')
- bimap :: Bifunctor p => (a -> b) -> (c -> d) -> p a c -> p b d
- toLower :: Char -> Char
- partitionEithers :: [Either a b] -> ([a], [b])
- toList :: Foldable t => t a -> [a]
- traverse_ :: (Foldable t, Applicative f) => (a -> f b) -> t a -> f ()
- on :: (b -> b -> c) -> (a -> b) -> a -> a -> c
- (&) :: a -> (a -> b) -> b
- intercalate :: [a] -> [[a]] -> [a]
- sortOn :: Ord b => (a -> b) -> [a] -> [a]
- sortBy :: (a -> a -> Ordering) -> [a] -> [a]
- nub :: Eq a => [a] -> [a]
- catMaybes :: [Maybe a] -> [a]
- fromMaybe :: a -> Maybe a -> a
- isJust :: Maybe a -> Bool
- isNothing :: Maybe a -> Bool
- data ByteString
- fromUTF8BS :: ByteString -> String
- toUTF8BS :: String -> ByteString
- pack' :: Newtype o n => (o -> n) -> o -> n
- unpack' :: Newtype o n => (o -> n) -> n -> o
- data Set a
- dropExtension :: FilePath -> FilePath
- splitDirectories :: FilePath -> [FilePath]
- catchError :: MonadError e m => m a -> (e -> m a) -> m a
- throwError :: MonadError e m => e -> m a
- traverseOf :: Applicative f => ((a -> f b) -> s -> f t) -> (a -> f b) -> s -> f t
- over :: ASetter s t a b -> (a -> b) -> s -> t
- view :: Getting a s a -> s -> a
- _1 :: Functor f => (a -> f b) -> (a, c) -> f (b, c)
Control.Arrow
(&&&) :: Arrow a => a b c -> a b c' -> a b (c, c') infixr 3 #
Fanout: send the input to both argument arrows and combine their output.
The default definition may be overridden with a more efficient version if desired.
Data.Bifunctor
Data.Char
Convert a letter to the corresponding lower-case letter, if any. Any other character is returned unchanged.
Data.Either
partitionEithers :: [Either a b] -> ([a], [b]) #
Partitions a list of Either
into two lists.
All the Left
elements are extracted, in order, to the first
component of the output. Similarly the Right
elements are extracted
to the second component of the output.
Examples
Basic usage:
>>>
let list = [ Left "foo", Right 3, Left "bar", Right 7, Left "baz" ]
>>>
partitionEithers list
(["foo","bar","baz"],[3,7])
The pair returned by
should be the same
pair as partitionEithers
x(
:lefts
x, rights
x)
>>>
let list = [ Left "foo", Right 3, Left "bar", Right 7, Left "baz" ]
>>>
partitionEithers list == (lefts list, rights list)
True
Data.Foldable
traverse_ :: (Foldable t, Applicative f) => (a -> f b) -> t a -> f () #
Map each element of a structure to an action, evaluate these
actions from left to right, and ignore the results. For a version
that doesn't ignore the results see traverse
.
Data.Function
Data.List
intercalate :: [a] -> [[a]] -> [a] #
intercalate
xs xss
is equivalent to (
.
It inserts the list concat
(intersperse
xs xss))xs
in between the lists in xss
and concatenates the
result.
>>>
intercalate ", " ["Lorem", "ipsum", "dolor"]
"Lorem, ipsum, dolor"
sortOn :: Ord b => (a -> b) -> [a] -> [a] #
Sort a list by comparing the results of a key function applied to each
element. sortOn f
is equivalent to sortBy (comparing f)
, but has the
performance advantage of only evaluating f
once for each element in the
input list. This is called the decorate-sort-undecorate paradigm, or
Schwartzian transform.
Elements are arranged from from lowest to highest, keeping duplicates in the order they appeared in the input.
>>>
sortOn fst [(2, "world"), (4, "!"), (1, "Hello")]
[(1,"Hello"),(2,"world"),(4,"!")]
Since: base-4.8.0.0
O(n^2). The nub
function removes duplicate elements from a list.
In particular, it keeps only the first occurrence of each element.
(The name nub
means `essence'.)
It is a special case of nubBy
, which allows the programmer to supply
their own equality test.
>>>
nub [1,2,3,4,3,2,1,2,4,3,5]
[1,2,3,4,5]
Data.Maybe
catMaybes :: [Maybe a] -> [a] #
The catMaybes
function takes a list of Maybe
s and returns
a list of all the Just
values.
Examples
Basic usage:
>>>
catMaybes [Just 1, Nothing, Just 3]
[1,3]
When constructing a list of Maybe
values, catMaybes
can be used
to return all of the "success" results (if the list is the result
of a map
, then mapMaybe
would be more appropriate):
>>>
import Text.Read ( readMaybe )
>>>
[readMaybe x :: Maybe Int | x <- ["1", "Foo", "3"] ]
[Just 1,Nothing,Just 3]>>>
catMaybes $ [readMaybe x :: Maybe Int | x <- ["1", "Foo", "3"] ]
[1,3]
fromMaybe :: a -> Maybe a -> a #
The fromMaybe
function takes a default value and and Maybe
value. If the Maybe
is Nothing
, it returns the default values;
otherwise, it returns the value contained in the Maybe
.
Examples
Basic usage:
>>>
fromMaybe "" (Just "Hello, World!")
"Hello, World!"
>>>
fromMaybe "" Nothing
""
Read an integer from a string using readMaybe
. If we fail to
parse an integer, we want to return 0
by default:
>>>
import Text.Read ( readMaybe )
>>>
fromMaybe 0 (readMaybe "5")
5>>>
fromMaybe 0 (readMaybe "")
0
Packages
bytestring
data ByteString #
A space-efficient representation of a Word8
vector, supporting many
efficient operations.
A ByteString
contains 8-bit bytes, or by using the operations from
Data.ByteString.Char8 it can be interpreted as containing 8-bit
characters.
Instances
Cabal
fromUTF8BS :: ByteString -> String #
Decode String
from UTF8-encoded ByteString
Invalid data in the UTF8 stream (this includes code-points U+D800
through U+DFFF
) will be decoded as the replacement character (U+FFFD
).
toUTF8BS :: String -> ByteString #
Encode String
to to UTF8-encoded ByteString
Code-points in the U+D800
-U+DFFF
range will be encoded
as the replacement character (i.e. U+FFFD
).
containers
A set of values a
.
Instances
Foldable Set | |
Defined in Data.Set.Internal fold :: Monoid m => Set m -> m # foldMap :: Monoid m => (a -> m) -> Set a -> m # foldr :: (a -> b -> b) -> b -> Set a -> b # foldr' :: (a -> b -> b) -> b -> Set a -> b # foldl :: (b -> a -> b) -> b -> Set a -> b # foldl' :: (b -> a -> b) -> b -> Set a -> b # foldr1 :: (a -> a -> a) -> Set a -> a # foldl1 :: (a -> a -> a) -> Set a -> a # elem :: Eq a => a -> Set a -> Bool # maximum :: Ord a => Set a -> a # | |
Eq1 Set | Since: containers-0.5.9 |
Ord1 Set | Since: containers-0.5.9 |
Defined in Data.Set.Internal | |
Show1 Set | Since: containers-0.5.9 |
Ord a => IsList (Set a) | Since: containers-0.5.6.2 |
Eq a => Eq (Set a) | |
(Data a, Ord a) => Data (Set a) | |
Defined in Data.Set.Internal gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Set a -> c (Set a) # gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (Set a) # dataTypeOf :: Set a -> DataType # dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (Set a)) # dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (Set a)) # gmapT :: (forall b. Data b => b -> b) -> Set a -> Set a # gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Set a -> r # gmapQr :: (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Set a -> r # gmapQ :: (forall d. Data d => d -> u) -> Set a -> [u] # gmapQi :: Int -> (forall d. Data d => d -> u) -> Set a -> u # gmapM :: Monad m => (forall d. Data d => d -> m d) -> Set a -> m (Set a) # gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Set a -> m (Set a) # gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Set a -> m (Set a) # | |
Ord a => Ord (Set a) | |
(Read a, Ord a) => Read (Set a) | |
Show a => Show (Set a) | |
Ord a => Semigroup (Set a) | Since: containers-0.5.7 |
Ord a => Monoid (Set a) | |
NFData a => NFData (Set a) | |
Defined in Data.Set.Internal | |
Newtype (Set a) (Set' sep wrapper a) | |
type Item (Set a) | |
Defined in Data.Set.Internal |
directory
dropExtension :: FilePath -> FilePath #
Remove last extension, and the "." preceding it.
dropExtension "/directory/path.ext" == "/directory/path" dropExtension x == fst (splitExtension x)
splitDirectories :: FilePath -> [FilePath] #
Just as splitPath
, but don't add the trailing slashes to each element.
splitDirectories "/directory/file.ext" == ["/","directory","file.ext"] splitDirectories "test/file" == ["test","file"] splitDirectories "/test/file" == ["/","test","file"] Windows: splitDirectories "C:\\test\\file" == ["C:\\", "test", "file"] Valid x => joinPath (splitDirectories x) `equalFilePath` x splitDirectories "" == [] Windows: splitDirectories "C:\\test\\\\\\file" == ["C:\\", "test", "file"] splitDirectories "/test///file" == ["/","test","file"]
exceptions
catchError :: MonadError e m => m a -> (e -> m a) -> m a #
A handler function to handle previous errors and return to normal execution. A common idiom is:
do { action1; action2; action3 } `catchError` handler
where the action
functions can call throwError
.
Note that handler
and the do-block must have the same return type.
throwError :: MonadError e m => e -> m a #
Is used within a monadic computation to begin exception processing.
Extras
Lens
traverseOf :: Applicative f => ((a -> f b) -> s -> f t) -> (a -> f b) -> s -> f t Source #