Copyright | (C) 2012-16 Edward Kmett |
---|---|
License | BSD-style (see the file LICENSE) |
Maintainer | Edward Kmett <ekmett@gmail.com> |
Stability | provisional |
Portability | non-portable |
Safe Haskell | Trustworthy |
Language | Haskell2010 |
Control.Lens.Review
Contents
Description
Synopsis
- type Review t b = forall p f. ( Choice p, Bifunctor p, Settable f) => Optic' p f t b
- type AReview t b = Optic' Tagged Identity t b
- unto :: ( Profunctor p, Bifunctor p, Functor f) => (b -> t) -> Optic p f s t a b
- un :: ( Profunctor p, Bifunctor p, Functor f) => Getting a s a -> Optic' p f a s
- re :: AReview t b -> Getter b t
- review :: MonadReader b m => AReview t b -> m t
- reviews :: MonadReader b m => AReview t b -> (t -> r) -> m r
- reuse :: MonadState b m => AReview t b -> m t
- reuses :: MonadState b m => AReview t b -> (t -> r) -> m r
- (#) :: AReview t b -> b -> t
-
class
Bifunctor
(p ::
Type
->
Type
->
Type
)
where
- bimap :: (a -> b) -> (c -> d) -> p a c -> p b d
- retagged :: ( Profunctor p, Bifunctor p) => p a b -> p s b
- class ( Profunctor p, Bifunctor p) => Reviewable p
- reviewing :: ( Bifunctor p, Functor f) => Optic Tagged Identity s t a b -> Optic' p f t b
Reviewing
re :: AReview t b -> Getter b t Source #
Turn a
Prism
or
Iso
around to build a
Getter
.
If you have an
Iso
,
from
is a more powerful version of this function
that will return an
Iso
instead of a mere
Getter
.
>>>
5 ^.re _Left
Left 5
>>>
6 ^.re (_Left.unto succ)
Left 7
review
≡view
.
re
reviews
≡views
.
re
reuse
≡use
.
re
reuses
≡uses
.
re
re
::Prism
s t a b ->Getter
b tre
::Iso
s t a b ->Getter
b t
review :: MonadReader b m => AReview t b -> m t Source #
This can be used to turn an
Iso
or
Prism
around and
view
a value (or the current environment) through it the other way.
review
≡view
.
re
review
.unto
≡id
>>>
review _Left "mustard"
Left "mustard"
>>>
review (unto succ) 5
6
Usually
review
is used in the
(->)
Monad
with a
Prism
or
Iso
, in which case it may be useful to think of
it as having one of these more restricted type signatures:
review
::Iso'
s a -> a -> sreview
::Prism'
s a -> a -> s
However, when working with a
Monad
transformer stack, it is sometimes useful to be able to
review
the current environment, in which case
it may be beneficial to think of it as having one of these slightly more liberal type signatures:
review
::MonadReader
a m =>Iso'
s a -> m sreview
::MonadReader
a m =>Prism'
s a -> m s
reviews :: MonadReader b m => AReview t b -> (t -> r) -> m r Source #
This can be used to turn an
Iso
or
Prism
around and
view
a value (or the current environment) through it the other way,
applying a function.
reviews
≡views
.
re
reviews
(unto
f) g ≡ g.
f
>>>
reviews _Left isRight "mustard"
False
>>>
reviews (unto succ) (*2) 3
8
Usually this function is used in the
(->)
Monad
with a
Prism
or
Iso
, in which case it may be useful to think of
it as having one of these more restricted type signatures:
reviews
::Iso'
s a -> (s -> r) -> a -> rreviews
::Prism'
s a -> (s -> r) -> a -> r
However, when working with a
Monad
transformer stack, it is sometimes useful to be able to
review
the current environment, in which case
it may be beneficial to think of it as having one of these slightly more liberal type signatures:
reviews
::MonadReader
a m =>Iso'
s a -> (s -> r) -> m rreviews
::MonadReader
a m =>Prism'
s a -> (s -> r) -> m r
reuse :: MonadState b m => AReview t b -> m t Source #
This can be used to turn an
Iso
or
Prism
around and
use
a value (or the current environment) through it the other way.
reuse
≡use
.
re
reuse
.
unto
≡gets
>>>
evalState (reuse _Left) 5
Left 5
>>>
evalState (reuse (unto succ)) 5
6
reuse
::MonadState
a m =>Prism'
s a -> m sreuse
::MonadState
a m =>Iso'
s a -> m s
reuses :: MonadState b m => AReview t b -> (t -> r) -> m r Source #
This can be used to turn an
Iso
or
Prism
around and
use
the current state through it the other way,
applying a function.
reuses
≡uses
.
re
reuses
(unto
f) g ≡gets
(g.
f)
>>>
evalState (reuses _Left isLeft) (5 :: Int)
True
reuses
::MonadState
a m =>Prism'
s a -> (s -> r) -> m rreuses
::MonadState
a m =>Iso'
s a -> (s -> r) -> m r
(#) :: AReview t b -> b -> t infixr 8 Source #
An infix alias for
review
.
unto
f # x ≡ f x l # x ≡ x^.
re
l
This is commonly used when using a
Prism
as a smart constructor.
>>>
_Left # 4
Left 4
But it can be used for any
Prism
>>>
base 16 # 123
"7b"
(#) ::Iso'
s a -> a -> s (#) ::Prism'
s a -> a -> s (#) ::Review
s a -> a -> s (#) ::Equality'
s a -> a -> s
class Bifunctor (p :: Type -> Type -> Type ) where Source #
A bifunctor is a type constructor that takes
two type arguments and is a functor in
both
arguments. That
is, unlike with
Functor
, a type constructor such as
Either
does not need to be partially applied for a
Bifunctor
instance, and the methods in this class permit mapping
functions over the
Left
value or the
Right
value,
or both at the same time.
Formally, the class
Bifunctor
represents a bifunctor
from
Hask
->
Hask
.
Intuitively it is a bifunctor where both the first and second arguments are covariant.
You can define a
Bifunctor
by either defining
bimap
or by
defining both
first
and
second
.
If you supply
bimap
, you should ensure that:
bimap
id
id
≡id
If you supply
first
and
second
, ensure:
first
id
≡id
second
id
≡id
If you supply both, you should also ensure:
bimap
f g ≡first
f.
second
g
These ensure by parametricity:
bimap
(f.
g) (h.
i) ≡bimap
f h.
bimap
g ifirst
(f.
g) ≡first
f.
first
gsecond
(f.
g) ≡second
f.
second
g
Since: base-4.8.0.0
Methods
Instances
retagged :: ( Profunctor p, Bifunctor p) => p a b -> p s b Source #
This is a profunctor used internally to implement Review
It plays a role similar to that of
Accessor
or
Const
do for
Control.Lens.Getter
class ( Profunctor p, Bifunctor p) => Reviewable p Source #
This class is provided mostly for backwards compatibility with lens 3.8, but it can also shorten type signatures.
Instances
( Profunctor p, Bifunctor p) => Reviewable p Source # | |
Defined in Control.Lens.Internal.Review |