Copyright | (C) 2012-15 Edward Kmett, 2012-13 Michael Sloan |
---|---|
License | BSD-style (see the file LICENSE) |
Maintainer | Edward Kmett <ekmett@gmail.com> |
Stability | experimental |
Portability | non-portable |
Safe Haskell | Trustworthy |
Language | Haskell98 |
- makeLenses :: Name -> DecsQ
- makeLensesFor :: [(String, String)] -> Name -> DecsQ
- makeClassy :: Name -> DecsQ
- makeClassyFor :: String -> String -> [(String, String)] -> Name -> DecsQ
- makeClassy_ :: Name -> DecsQ
- makePrisms :: Name -> DecsQ
- makeClassyPrisms :: Name -> DecsQ
- makeWrapped :: Name -> DecsQ
- makeFields :: Name -> DecsQ
- declareLenses :: DecsQ -> DecsQ
- declareLensesFor :: [(String, String)] -> DecsQ -> DecsQ
- declareClassy :: DecsQ -> DecsQ
- declareClassyFor :: [(String, (String, String))] -> [(String, String)] -> DecsQ -> DecsQ
- declarePrisms :: DecsQ -> DecsQ
- declareWrapped :: DecsQ -> DecsQ
- declareFields :: DecsQ -> DecsQ
- makeLensesWith :: LensRules -> Name -> DecsQ
- declareLensesWith :: LensRules -> DecsQ -> DecsQ
- defaultFieldRules :: LensRules
- camelCaseFields :: LensRules
- underscoreFields :: LensRules
- abbreviatedFields :: LensRules
- data LensRules
- data DefName
- lensRules :: LensRules
- lensRulesFor :: [(String, String)] -> LensRules
- classyRules :: LensRules
- classyRules_ :: LensRules
- lensField :: Lens' LensRules (Name -> [Name] -> Name -> [DefName])
- lensClass :: Lens' LensRules (Name -> Maybe (Name, Name))
- simpleLenses :: Lens' LensRules Bool
- createClass :: Lens' LensRules Bool
- generateSignatures :: Lens' LensRules Bool
- generateUpdateableOptics :: Lens' LensRules Bool
- generateLazyPatterns :: Lens' LensRules Bool
Constructing Lenses Automatically
makeLenses :: Name -> DecsQ Source
Build lenses (and traversals) with a sensible default configuration.
e.g.
data FooBar = Foo { _x, _y ::Int
} | Bar { _x ::Int
}makeLenses
''FooBar
will create
x ::Lens'
FooBarInt
x f (Foo a b) = (\a' -> Foo a' b) <$> f a x f (Bar a) = Bar <$> f a y ::Traversal'
FooBarInt
y f (Foo a b) = (\b' -> Foo a b') <$> f b y _ c@(Bar _) = pure c
makeLenses
=makeLensesWith
lensRules
makeLensesFor :: [(String, String)] -> Name -> DecsQ Source
Derive lenses and traversals, specifying explicit pairings
of (fieldName, lensName)
.
If you map multiple names to the same label, and it is present in the same
constructor then this will generate a Traversal
.
e.g.
makeLensesFor
[("_foo", "fooLens"), ("baz", "lbaz")] ''FoomakeLensesFor
[("_barX", "bar"), ("_barY", "bar")] ''Bar
makeClassy :: Name -> DecsQ Source
Make lenses and traversals for a type, and create a class when the type has no arguments.
e.g.
data Foo = Foo { _fooX, _fooY ::Int
}makeClassy
''Foo
will create
class HasFoo t where foo ::Lens'
t Foo fooX ::Lens'
tInt
fooX = foo . go where go f (Foo x y) = (\x' -> Foo x' y) <$> f x fooY ::Lens'
tInt
fooY = foo . go where go f (Foo x y) = (\y' -> Foo x y') <$> f y instance HasFoo Foo where foo = id
makeClassy
=makeLensesWith
classyRules
makeClassyFor :: String -> String -> [(String, String)] -> Name -> DecsQ Source
Derive lenses and traversals, using a named wrapper class, and
specifying explicit pairings of (fieldName, traversalName)
.
Example usage:
makeClassyFor
"HasFoo" "foo" [("_foo", "fooLens"), ("bar", "lbar")] ''Foo
makeClassy_ :: Name -> DecsQ Source
Make lenses and traversals for a type, and create a class when the type
has no arguments. Works the same as makeClassy
except that (a) it
expects that record field names do not begin with an underscore, (b) all
record fields are made into lenses, and (c) the resulting lens is prefixed
with an underscore.
Generate a Prism
for each constructor of a data type.
Isos generated when possible.
Reviews are created for constructors with existentially
quantified constructors and GADTs.
e.g.
data FooBarBaz a = Foo Int | Bar a | Baz Int Char makePrisms ''FooBarBaz
will create
_Foo :: Prism' (FooBarBaz a) Int _Bar :: Prism (FooBarBaz a) (FooBarBaz b) a b _Baz :: Prism' (FooBarBaz a) (Int, Char)
Generate a Prism
for each constructor of a data type
and combine them into a single class. No Isos are created.
Reviews are created for constructors with existentially
quantified constructors and GADTs.
e.g.
data FooBarBaz a = Foo Int | Bar a | Baz Int Char makeClassyPrisms ''FooBarBaz
will create
class AsFooBarBaz s a | s -> a where _FooBarBaz :: Prism' s (FooBarBaz a) _Foo :: Prism' s Int _Bar :: Prism' s a _Baz :: Prism' s (Int,Char) _Foo = _FooBarBaz . _Foo _Bar = _FooBarBaz . _Bar _Baz = _FooBarBaz . _Baz instance AsFooBarBaz (FooBarBaz a) a
Generate an As class of prisms. Names are selected by prefixing the constructor name with an underscore. Constructors with multiple fields will construct Prisms to tuples of those fields.
makeWrapped :: Name -> DecsQ Source
Build Wrapped
instance for a given newtype
makeFields :: Name -> DecsQ Source
Generate overloaded field accessors.
e.g
data Foo a = Foo { _fooX ::Int
, _fooY : a } newtype Bar = Bar { _barX ::Char
} makeFields ''Foo makeFields ''Bar
will create
_fooXLens :: Lens' (Foo a) Int _fooYLens :: Lens (Foo a) (Foo b) a b class HasX s a | s -> a where x :: Lens' s a instance HasX (Foo a) Int where x = _fooXLens class HasY s a | s -> a where y :: Lens' s a instance HasY (Foo a) a where y = _fooYLens _barXLens :: Iso' Bar Char instance HasX Bar Char where x = _barXLens
For details, see camelCaseFields
.
makeFields =makeLensesWith
defaultFieldRules
Constructing Lenses Given a Declaration Quote
declareLenses :: DecsQ -> DecsQ Source
declareLensesFor :: [(String, String)] -> DecsQ -> DecsQ Source
Similar to makeLensesFor
, but takes a declaration quote.
declareClassy :: DecsQ -> DecsQ Source
For each record in the declaration quote, make lenses and traversals for it, and create a class when the type has no arguments. All record syntax in the input will be stripped off.
e.g.
declareClassy [d| data Foo = Foo { fooX, fooY ::Int
} derivingShow
|]
will create
data Foo = FooInt
Int
derivingShow
class HasFoo t where foo ::Lens'
t Foo instance HasFoo Foo where foo =id
fooX, fooY :: HasFoo t =>Lens'
tInt
declareClassyFor :: [(String, (String, String))] -> [(String, String)] -> DecsQ -> DecsQ Source
Similar to makeClassyFor
, but takes a declaration quote.
declarePrisms :: DecsQ -> DecsQ Source
Generate a Prism
for each constructor of each data type.
e.g.
declarePrisms [d| data Exp = Lit Int | Var String | Lambda{ bound::String, body::Exp } |]
will create
data Exp = Lit Int | Var String | Lambda { bound::String, body::Exp } _Lit ::Prism'
Exp Int _Var ::Prism'
Exp String _Lambda ::Prism'
Exp (String, Exp)
declareWrapped :: DecsQ -> DecsQ Source
Build Wrapped
instance for each newtype.
declareFields :: DecsQ -> DecsQ Source
declareFields =declareLensesWith
defaultFieldRules
Configuring Lenses
makeLensesWith :: LensRules -> Name -> DecsQ Source
Build lenses with a custom configuration.
declareLensesWith :: LensRules -> DecsQ -> DecsQ Source
Declare lenses for each records in the given declarations, using the
specified LensRules
. Any record syntax in the input will be stripped
off.
camelCaseFields :: LensRules Source
Field rules for fields in the form prefixFieldname or _prefixFieldname
If you want all fields to be lensed, then there is no reason to use an _
before the prefix.
If any of the record fields leads with an _
then it is assume a field without an _
should not have a lens created.
Note: The prefix
must be the same as the typename (with the first
letter lowercased). This is a change from lens versions before lens 4.5.
If you want the old behaviour, use makeLensesWith
abbreviatedFields
underscoreFields :: LensRules Source
Field rules for fields in the form _prefix_fieldname
abbreviatedFields :: LensRules Source
Field rules fields in the form prefixFieldname or _prefixFieldname
If you want all fields to be lensed, then there is no reason to use an _
before the prefix.
If any of the record fields leads with an _
then it is assume a field without an _
should not have a lens created.
Note that prefix
may be any string of characters that are not uppercase
letters. (In particular, it may be arbitrary string of lowercase letters
and numbers) This is the behavior that defaultFieldRules
had in lens
4.4 and earlier.
Name to give to generated field optics.
TopName Name | Simple top-level definiton name |
MethodName Name Name | makeFields-style class name and method name |
Rules for making fairly simple partial lenses, ignoring the special cases for isomorphisms and traversals, and not making any classes.
Construct a LensRules
value for generating top-level definitions
using the given map from field names to definition names.
classyRules :: LensRules Source
Rules for making lenses and traversals that precompose another Lens
.
lensField :: Lens' LensRules (Name -> [Name] -> Name -> [DefName]) Source
Lens'
to access the convention for naming fields in our LensRules
.
Defaults to stripping the _ off of the field name, lowercasing the name, and skipping the field if it doesn't start with an '_'. The field naming rule provides the names of all fields in the type as well as the current field. This extra generality enables field naming conventions that depend on the full set of names in a type.
The field naming rule has access to the type name, the names of all the field of that type (including the field being named), and the name of the field being named.
TypeName -> FieldNames -> FieldName -> DefinitionNames
lensClass :: Lens' LensRules (Name -> Maybe (Name, Name)) Source
Retrieve options such as the name of the class and method to put in it to build a class around monomorphic data types. Classy lenses are generated when this naming convention is provided. TypeName -> Maybe (ClassName, MainMethodName)
generateSignatures :: Lens' LensRules Bool Source
Indicate whether or not to supply the signatures for the generated lenses.
Disabling this can be useful if you want to provide a more restricted type signature or if you want to supply hand-written haddocks.
generateLazyPatterns :: Lens' LensRules Bool Source
Generate optics using lazy pattern matches. This can allow fields of an undefined value to be initialized with lenses:
data Foo = Foo {_x :: Int, _y :: Bool} deriving ShowmakeLensesWith
(lensRules
&generateLazyPatterns
.~ True) ''Foo
> undefined & x .~ 8 & y .~ True Foo {_x = 8, _y = True}
The downside of this flag is that it can lead to space-leaks and code-size/compile-time increases when generated for large records. By default this flag is turned off, and strict optics are generated.
When using lazy optics the strict optic can be recovered by composing
with $!
:
strictOptic = ($!) . lazyOptic