| Copyright | (C) 2017 Csongor Kiss |
|---|---|
| License | BSD3 |
| Maintainer | Csongor Kiss <kiss.csongor.kiss@gmail.com> |
| Stability | experimental |
| Portability | non-portable |
| Safe Haskell | Safe |
| Language | Haskell2010 |
Data.Generics.Product
Contents
Description
Magic product operations using Generics
These classes need not be instantiated manually, as GHC can automatically
prove valid instances via Generics. Only the Generic class needs to
be derived (see examples).
- class HasAny sel a s | s sel k -> a where
- class HasField field a s | s field -> a where
- class HasPosition i a s | s i -> a where
- class HasType a s where
- class Subtype sup sub where
Lenses
class HasAny sel a s | s sel k -> a where Source #
Records that have generic lenses.
Minimal complete definition
Methods
A lens that focuses on a part of a product as identified by some
selector. Currently supported selectors are field names, positions and
unique types. Compatible with the lens package's Lens
type.
>>>human ^. the @Int50>>>human ^. the @"name""Tunyasz">>>human ^. the @3"London"
class HasField field a s | s field -> a where Source #
Records that have a field with a given name.
Methods
A lens that focuses on a field with a given name. Compatible with the
lens package's Lens type.
>>>human ^. field @"age"50>>>human & field @"name" .~ "Tamas"Human {name = "Tamas", age = 50, address = "London"}
Get field
>>>getField @"name" human"Tunyasz"
setField :: a -> s -> s Source #
Set field
>>>setField @"age" (setField @"name" "Tamas" human) 30Human {name = "Tamas", age = 30, address = "London"}
class HasPosition i a s | s i -> a where Source #
Records that have a field at a given position.
Minimal complete definition
Methods
position :: Lens' s a Source #
A lens that focuses on a field at a given position. Compatible with the
lens package's Lens type.
>>>human ^. position @1"Tunyasz">>>human & position @2 .~ "Berlin"Human {name = "Tunyasz", age = 50, address = "Berlin"}
getPosition :: s -> a Source #
Get positional field
>>>getPosition @1 human"Tunyasz"
setPosition :: a -> s -> s Source #
Set positional field
>>>setPosition @2 (setField @1 "Tamas" human) 30Human "Tamas" 30 "London"
Instances
| (Generic s, ErrorUnless i s ((&&) ((<?) 0 i) ((<=?) i (Size (Rep s)))), GHasPosition 1 i (Rep s) a) => HasPosition i a s Source # | |
Subtype relationships
class Subtype sup sub where Source #
Structural subtype relationship
sub is a (structural) subtype of sup, if its fields are a subset of
those of sup.
Methods
super :: Lens' sub sup Source #
Structural subtype lens. Given a subtype relationship sub :< sup,
we can focus on the sub structure of sup.
>>>human ^. super @AnimalAnimal {name = "Tunyasz", age = 50}
>>>set (super @Animal) (Animal "dog" 10) humanHuman {name = "dog", age = 10, address = "London"}
Cast the more specific subtype to the more general supertype
>>>upcast human :: AnimalAnimal {name = "Tunyasz", age = 50}
smash :: sup -> sub -> sub Source #
Plug a smaller structure into a larger one
>>>smash (Animal "dog" 10) humanHuman {name = "dog", age = 10, address = "London"}