| Safe Haskell | None |
|---|---|
| Language | Haskell2010 |
Data.Lazify
Description
Record types in Haskell can be made lazy through lazy pattern matching. This module offers functions for making them lazy generically.
- class Lazifiable a where
- genericLazify :: (Generic a, GLazifiable (Rep a)) => a -> a
- ($~) :: forall rep a (b :: TYPE rep). Lazifiable a => (a -> b) -> a -> b
Documentation
class Lazifiable a where Source #
A class for types that can be lazified. A generic
default is provided for convenience. To lazify a type using
its generic representation, use genericLazify.
Methods
Lazily rewrap a record. Applying lazify to a record and then
pattern matching on it strictly is equivalent to pattern matching
on it lazily.
strictFirst :: (a -> a') -> (a, b) -> (a', b) strictFirst f (a, b) = (f a, b) lazyFirst :: (a -> a') -> (a, b) -> (a', b) lazyFirst f = strictFirst f . lazify -- Equivalently lazyFirst f ~(a, b) = (f a, b)
lazify :: (Generic a, GLazifiable (Rep a)) => a -> a Source #
Lazily rewrap a record. Applying lazify to a record and then
pattern matching on it strictly is equivalent to pattern matching
on it lazily.
strictFirst :: (a -> a') -> (a, b) -> (a', b) strictFirst f (a, b) = (f a, b) lazyFirst :: (a -> a') -> (a, b) -> (a', b) lazyFirst f = strictFirst f . lazify -- Equivalently lazyFirst f ~(a, b) = (f a, b)
Instances
genericLazify :: (Generic a, GLazifiable (Rep a)) => a -> a Source #
Lazify a record using its generic representation.
Note that newtypes are treated specially: a newtype is lazified
by lazifying its underlying type using its Lazifiable instance.
($~) :: forall rep a (b :: TYPE rep). Lazifiable a => (a -> b) -> a -> b Source #
Apply a function to a lazified value.