Copyright | (c) Fumiaki Kinoshita 2020 |
---|---|
License | BSD-style (see the file LICENSE) |
Maintainer | fumiexcel@gmail.com |
Stability | experimental |
Portability | portable |
Safe Haskell | Safe |
Language | Haskell2010 |
HumblePrelude with uncontroversial, frequently used types and functions
Synopsis
- liftA2 :: Applicative f => (a -> b -> c) -> f a -> f b -> f c
- class Applicative f => Alternative (f :: Type -> Type) where
- guard :: Alternative f => Bool -> f ()
- when :: Applicative f => Bool -> f () -> f ()
- unless :: Applicative f => Bool -> f () -> f ()
- (&) :: a -> (a -> b) -> b
- fix :: (a -> a) -> a
- (<&>) :: Functor f => f a -> (a -> b) -> f b
- void :: Functor f => f a -> f ()
- comparing :: Ord a => (b -> a) -> b -> b -> Ordering
- traverse_ :: (Foldable t, Applicative f) => (a -> f b) -> t a -> f ()
- for_ :: (Foldable t, Applicative f) => t a -> (a -> f b) -> f ()
- foldl' :: Foldable t => (b -> a -> b) -> b -> t a -> b
- for :: (Traversable t, Applicative f) => t a -> (a -> f b) -> f (t b)
- data ByteString
- data Constraint
- class Generic a
- class Monad m => MonadIO (m :: Type -> Type) where
- class NFData a
- data Proxy (t :: k) :: forall k. k -> Type = Proxy
- data Text
- type Type = Type
- module HumblePrelude
Control.Applicative
liftA2 :: Applicative f => (a -> b -> c) -> f a -> f b -> f c #
class Applicative f => Alternative (f :: Type -> Type) where #
A monoid on applicative functors.
If defined, some
and many
should be the least solutions
of the equations:
Instances
Control.Monad
guard :: Alternative f => Bool -> f () #
Conditional failure of Alternative
computations. Defined by
guard True =pure
() guard False =empty
Examples
Common uses of guard
include conditionally signaling an error in
an error monad and conditionally rejecting the current choice in an
Alternative
-based parser.
As an example of signaling an error in the error monad Maybe
,
consider a safe division function safeDiv x y
that returns
Nothing
when the denominator y
is zero and
otherwise. For example:Just
(x `div`
y)
>>> safeDiv 4 0 Nothing >>> safeDiv 4 2 Just 2
A definition of safeDiv
using guards, but not guard
:
safeDiv :: Int -> Int -> Maybe Int safeDiv x y | y /= 0 = Just (x `div` y) | otherwise = Nothing
A definition of safeDiv
using guard
and Monad
do
-notation:
safeDiv :: Int -> Int -> Maybe Int safeDiv x y = do guard (y /= 0) return (x `div` y)
when :: Applicative f => Bool -> f () -> f () #
Conditional execution of Applicative
expressions. For example,
when debug (putStrLn "Debugging")
will output the string Debugging
if the Boolean value debug
is True
, and otherwise do nothing.
unless :: Applicative f => Bool -> f () -> f () #
The reverse of when
.
Data.Function
is the least fixed point of the function fix
ff
,
i.e. the least defined x
such that f x = x
.
For example, we can write the factorial function using direct recursion as
>>>
let fac n = if n <= 1 then 1 else n * fac (n-1) in fac 5
120
This uses the fact that Haskell’s let
introduces recursive bindings. We can
rewrite this definition using fix
,
>>>
fix (\rec n -> if n <= 1 then 1 else n * rec (n-1)) 5
120
Instead of making a recursive call, we introduce a dummy parameter rec
;
when used within fix
, this parameter then refers to fix'
argument, hence
the recursion is reintroduced.
Data.Functor
void :: Functor f => f a -> f () #
discards or ignores the result of evaluation, such
as the return value of an void
valueIO
action.
Examples
Replace the contents of a
with unit:Maybe
Int
>>>
void Nothing
Nothing>>>
void (Just 3)
Just ()
Replace the contents of an
with unit,
resulting in an Either
Int
Int
:Either
Int
'()'
>>>
void (Left 8675309)
Left 8675309>>>
void (Right 8675309)
Right ()
Replace every element of a list with unit:
>>>
void [1,2,3]
[(),(),()]
Replace the second element of a pair with unit:
>>>
void (1,2)
(1,())
Discard the result of an IO
action:
>>>
mapM print [1,2]
1 2 [(),()]>>>
void $ mapM print [1,2]
1 2
Data.Ord
comparing :: Ord a => (b -> a) -> b -> b -> Ordering #
comparing p x y = compare (p x) (p y)
Useful combinator for use in conjunction with the xxxBy
family
of functions from Data.List, for example:
... sortBy (comparing fst) ...
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
.
for_ :: (Foldable t, Applicative f) => t a -> (a -> f b) -> f () #
foldl' :: Foldable t => (b -> a -> b) -> b -> t a -> b #
Left-associative fold of a structure but with strict application of the operator.
This ensures that each step of the fold is forced to weak head normal
form before being applied, avoiding the collection of thunks that would
otherwise occur. This is often what you want to strictly reduce a finite
list to a single, monolithic result (e.g. length
).
For a general Foldable
structure this should be semantically identical
to,
foldl f z =foldl'
f z .toList
Data.Traversable
for :: (Traversable t, Applicative f) => t a -> (a -> f b) -> f (t b) #
Common types
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
data Constraint #
The kind of constraints, like Show a
Representable types of kind *
.
This class is derivable in GHC with the DeriveGeneric
flag on.
A Generic
instance must satisfy the following laws:
from
.to
≡id
to
.from
≡id
Instances
A class of types that can be fully evaluated.
Since: deepseq-1.1.0.0
Instances
NFData Bool | |
Defined in Control.DeepSeq | |
NFData Char | |
Defined in Control.DeepSeq | |
NFData Double | |
Defined in Control.DeepSeq | |
NFData Float | |
Defined in Control.DeepSeq | |
NFData Int | |
Defined in Control.DeepSeq | |
NFData Int8 | |
Defined in Control.DeepSeq | |
NFData Int16 | |
Defined in Control.DeepSeq | |
NFData Int32 | |
Defined in Control.DeepSeq | |
NFData Int64 | |
Defined in Control.DeepSeq | |
NFData Integer | |
Defined in Control.DeepSeq | |
NFData Natural | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
NFData Ordering | |
Defined in Control.DeepSeq | |
NFData Word | |
Defined in Control.DeepSeq | |
NFData Word8 | |
Defined in Control.DeepSeq | |
NFData Word16 | |
Defined in Control.DeepSeq | |
NFData Word32 | |
Defined in Control.DeepSeq | |
NFData Word64 | |
Defined in Control.DeepSeq | |
NFData CallStack | Since: deepseq-1.4.2.0 |
Defined in Control.DeepSeq | |
NFData () | |
Defined in Control.DeepSeq | |
NFData TyCon | NOTE: Prior to Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
NFData Void | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
NFData Unique | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
NFData Version | Since: deepseq-1.3.0.0 |
Defined in Control.DeepSeq | |
NFData ThreadId | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
NFData ExitCode | Since: deepseq-1.4.2.0 |
Defined in Control.DeepSeq | |
NFData MaskingState | Since: deepseq-1.4.4.0 |
Defined in Control.DeepSeq rnf :: MaskingState -> () # | |
NFData TypeRep | NOTE: Prior to Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
NFData All | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
NFData Any | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
NFData CChar | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
NFData CSChar | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
NFData CUChar | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
NFData CShort | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
NFData CUShort | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
NFData CInt | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
NFData CUInt | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
NFData CLong | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
NFData CULong | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
NFData CLLong | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
NFData CULLong | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
NFData CBool | Since: deepseq-1.4.3.0 |
Defined in Control.DeepSeq | |
NFData CFloat | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
NFData CDouble | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
NFData CPtrdiff | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
NFData CSize | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
NFData CWchar | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
NFData CSigAtomic | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq rnf :: CSigAtomic -> () # | |
NFData CClock | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
NFData CTime | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
NFData CUSeconds | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
NFData CSUSeconds | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq rnf :: CSUSeconds -> () # | |
NFData CFile | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
NFData CFpos | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
NFData CJmpBuf | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
NFData CIntPtr | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
NFData CUIntPtr | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
NFData CIntMax | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
NFData CUIntMax | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
NFData Fingerprint | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq rnf :: Fingerprint -> () # | |
NFData SrcLoc | Since: deepseq-1.4.2.0 |
Defined in Control.DeepSeq | |
NFData ByteString | |
Defined in Data.ByteString.Internal rnf :: ByteString -> () # | |
NFData FFIInfo | |
Defined in ByteCodeTypes | |
NFData ItblPtr | |
Defined in ByteCodeTypes | |
NFData UnlinkedBCO | |
Defined in ByteCodeTypes rnf :: UnlinkedBCO -> () # | |
NFData BCOPtr | |
Defined in ByteCodeTypes | |
NFData BCONPtr | |
Defined in ByteCodeTypes | |
NFData SrcSpan | |
NFData Module | |
NFData ModuleName | |
Defined in Module rnf :: ModuleName -> () # | |
NFData UnitId | |
NFData FastZString | |
Defined in FastString rnf :: FastZString -> () # | |
NFData OccName | |
NFData Name | |
NFData ZonedTime | |
Defined in Data.Time.LocalTime.Internal.ZonedTime | |
NFData LocalTime | |
Defined in Data.Time.LocalTime.Internal.LocalTime | |
NFData NameSort | |
NFData a => NFData [a] | |
Defined in Control.DeepSeq | |
NFData a => NFData (Maybe a) | |
Defined in Control.DeepSeq | |
NFData a => NFData (Ratio a) | |
Defined in Control.DeepSeq | |
NFData (Ptr a) | Since: deepseq-1.4.2.0 |
Defined in Control.DeepSeq | |
NFData (FunPtr a) | Since: deepseq-1.4.2.0 |
Defined in Control.DeepSeq | |
NFData a => NFData (Complex a) | |
Defined in Control.DeepSeq | |
NFData (Fixed a) | Since: deepseq-1.3.0.0 |
Defined in Control.DeepSeq | |
NFData a => NFData (Min a) | Since: deepseq-1.4.2.0 |
Defined in Control.DeepSeq | |
NFData a => NFData (Max a) | Since: deepseq-1.4.2.0 |
Defined in Control.DeepSeq | |
NFData a => NFData (First a) | Since: deepseq-1.4.2.0 |
Defined in Control.DeepSeq | |
NFData a => NFData (Last a) | Since: deepseq-1.4.2.0 |
Defined in Control.DeepSeq | |
NFData m => NFData (WrappedMonoid m) | Since: deepseq-1.4.2.0 |
Defined in Control.DeepSeq rnf :: WrappedMonoid m -> () # | |
NFData a => NFData (Option a) | Since: deepseq-1.4.2.0 |
Defined in Control.DeepSeq | |
NFData (StableName a) | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq rnf :: StableName a -> () # | |
NFData a => NFData (ZipList a) | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
NFData a => NFData (Identity a) | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
NFData (IORef a) | NOTE: Only strict in the reference and not the referenced value. Since: deepseq-1.4.2.0 |
Defined in Control.DeepSeq | |
NFData a => NFData (First a) | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
NFData a => NFData (Last a) | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
NFData a => NFData (Dual a) | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
NFData a => NFData (Sum a) | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
NFData a => NFData (Product a) | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
NFData a => NFData (Down a) | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
NFData (MVar a) | NOTE: Only strict in the reference and not the referenced value. Since: deepseq-1.4.2.0 |
Defined in Control.DeepSeq | |
NFData a => NFData (NonEmpty a) | Since: deepseq-1.4.2.0 |
Defined in Control.DeepSeq | |
NFData (a -> b) | This instance is for convenience and consistency with Since: deepseq-1.3.0.0 |
Defined in Control.DeepSeq | |
(NFData a, NFData b) => NFData (Either a b) | |
Defined in Control.DeepSeq | |
(NFData a, NFData b) => NFData (a, b) | |
Defined in Control.DeepSeq | |
(NFData a, NFData b) => NFData (Array a b) | |
Defined in Control.DeepSeq | |
(NFData a, NFData b) => NFData (Arg a b) | Since: deepseq-1.4.2.0 |
Defined in Control.DeepSeq | |
NFData (Proxy a) | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
NFData (STRef s a) | NOTE: Only strict in the reference and not the referenced value. Since: deepseq-1.4.2.0 |
Defined in Control.DeepSeq | |
(NFData a1, NFData a2, NFData a3) => NFData (a1, a2, a3) | |
Defined in Control.DeepSeq | |
NFData a => NFData (Const a b) | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
NFData (a :~: b) | Since: deepseq-1.4.3.0 |
Defined in Control.DeepSeq | |
(NFData a1, NFData a2, NFData a3, NFData a4) => NFData (a1, a2, a3, a4) | |
Defined in Control.DeepSeq | |
(NFData1 f, NFData1 g, NFData a) => NFData (Product f g a) | Since: deepseq-1.4.3.0 |
Defined in Control.DeepSeq | |
(NFData1 f, NFData1 g, NFData a) => NFData (Sum f g a) | Since: deepseq-1.4.3.0 |
Defined in Control.DeepSeq | |
NFData (a :~~: b) | Since: deepseq-1.4.3.0 |
Defined in Control.DeepSeq | |
(NFData a1, NFData a2, NFData a3, NFData a4, NFData a5) => NFData (a1, a2, a3, a4, a5) | |
Defined in Control.DeepSeq | |
(NFData1 f, NFData1 g, NFData a) => NFData (Compose f g a) | Since: deepseq-1.4.3.0 |
Defined in Control.DeepSeq | |
(NFData a1, NFData a2, NFData a3, NFData a4, NFData a5, NFData a6) => NFData (a1, a2, a3, a4, a5, a6) | |
Defined in Control.DeepSeq | |
(NFData a1, NFData a2, NFData a3, NFData a4, NFData a5, NFData a6, NFData a7) => NFData (a1, a2, a3, a4, a5, a6, a7) | |
Defined in Control.DeepSeq | |
(NFData a1, NFData a2, NFData a3, NFData a4, NFData a5, NFData a6, NFData a7, NFData a8) => NFData (a1, a2, a3, a4, a5, a6, a7, a8) | |
Defined in Control.DeepSeq | |
(NFData a1, NFData a2, NFData a3, NFData a4, NFData a5, NFData a6, NFData a7, NFData a8, NFData a9) => NFData (a1, a2, a3, a4, a5, a6, a7, a8, a9) | |
Defined in Control.DeepSeq |
data Proxy (t :: k) :: forall k. k -> Type #
Proxy
is a type that holds no data, but has a phantom parameter of
arbitrary type (or even kind). Its use is to provide type information, even
though there is no value available of that type (or it may be too costly to
create one).
Historically,
is a safer alternative to the
Proxy
:: Proxy
a'undefined :: a'
idiom.
>>>
Proxy :: Proxy (Void, Int -> Int)
Proxy
Proxy can even hold types of higher kinds,
>>>
Proxy :: Proxy Either
Proxy
>>>
Proxy :: Proxy Functor
Proxy
>>>
Proxy :: Proxy complicatedStructure
Proxy
Instances
Generic1 (Proxy :: k -> Type) | |
Monad (Proxy :: Type -> Type) | Since: base-4.7.0.0 |
Functor (Proxy :: Type -> Type) | Since: base-4.7.0.0 |
Applicative (Proxy :: Type -> Type) | Since: base-4.7.0.0 |
Foldable (Proxy :: Type -> Type) | Since: base-4.7.0.0 |
Defined in Data.Foldable fold :: Monoid m => Proxy m -> m # foldMap :: Monoid m => (a -> m) -> Proxy a -> m # foldr :: (a -> b -> b) -> b -> Proxy a -> b # foldr' :: (a -> b -> b) -> b -> Proxy a -> b # foldl :: (b -> a -> b) -> b -> Proxy a -> b # foldl' :: (b -> a -> b) -> b -> Proxy a -> b # foldr1 :: (a -> a -> a) -> Proxy a -> a # foldl1 :: (a -> a -> a) -> Proxy a -> a # elem :: Eq a => a -> Proxy a -> Bool # maximum :: Ord a => Proxy a -> a # minimum :: Ord a => Proxy a -> a # | |
Traversable (Proxy :: Type -> Type) | Since: base-4.7.0.0 |
Alternative (Proxy :: Type -> Type) | Since: base-4.9.0.0 |
MonadPlus (Proxy :: Type -> Type) | Since: base-4.9.0.0 |
NFData1 (Proxy :: Type -> Type) | Since: deepseq-1.4.3.0 |
Defined in Control.DeepSeq | |
Bounded (Proxy t) | Since: base-4.7.0.0 |
Enum (Proxy s) | Since: base-4.7.0.0 |
Eq (Proxy s) | Since: base-4.7.0.0 |
Ord (Proxy s) | Since: base-4.7.0.0 |
Read (Proxy t) | Since: base-4.7.0.0 |
Show (Proxy s) | Since: base-4.7.0.0 |
Ix (Proxy s) | Since: base-4.7.0.0 |
Generic (Proxy t) | |
Semigroup (Proxy s) | Since: base-4.9.0.0 |
Monoid (Proxy s) | Since: base-4.7.0.0 |
NFData (Proxy a) | Since: deepseq-1.4.0.0 |
Defined in Control.DeepSeq | |
type Rep1 (Proxy :: k -> Type) | Since: base-4.6.0.0 |
type Rep (Proxy t) | Since: base-4.6.0.0 |
A space efficient, packed, unboxed Unicode text type.
module HumblePrelude