Safe Haskell	None
Language	Haskell2010

Control.Lens.SplitEpi

Synopsis

data SplitEpi a b = SplitEpi {
- get :: a -> b
- reverseGet :: b -> a
}
normalize :: SplitEpi a b -> a -> a
composeSplitEpi :: SplitEpi a b -> SplitEpi b c -> SplitEpi a c
composeIso :: SplitEpi a b -> Iso' b c -> SplitEpi a c
fromIso :: Iso' a b -> SplitEpi a b

Documentation

data SplitEpi a b Source #

A split epimorphism, which we can think of as a weaker Iso a b where b is a "smaller" type. So `get . reverseGet` remains an identity but `reverseGet . get` is merely idempotent (i.e., it normalizes values in a).

The following statements hold: - reverseGet is a "section" of get, - get is a "retraction" of reverseGet, - b is a "retract" of a, - the pair `(get, reverseGet)` is a "splitting" of the idempotent `reverseGet . get`.

Constructors

SplitEpi
Fields get :: a -> b reverseGet :: b -> a

Instances

Invariant (SplitEpi a) Source #
Instance details Defined in Control.Lens.SplitEpi Methods invmap :: (a0 -> b) -> (b -> a0) -> SplitEpi a a0 -> SplitEpi a b #

normalize :: SplitEpi a b -> a -> a Source #

`reverseGet . get`, yielding a normalized formatted value. Subsequent get/reverseGet cycles are idempotent.

composeSplitEpi :: SplitEpi a b -> SplitEpi b c -> SplitEpi a c Source #

Compose with another SplitEpi.

composeIso :: SplitEpi a b -> Iso' b c -> SplitEpi a c Source #

Compose with an Iso.

fromIso :: Iso' a b -> SplitEpi a b Source #

An Isomorphism is trivially a SplitEpi.