Control.Lens.SplitEpi

Documentation

data SplitEpi a b

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)

Defined in Control.Lens.SplitEpi

Methods

invmap :: (a0 -> b) -> (b -> a0) -> SplitEpi a a0 -> SplitEpi a b

normalize :: SplitEpi a b -> a -> a

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

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

Compose with another SplitEpi.

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

Compose with an Iso.

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

An Isomorphism is trivially a SplitEpi.