Module

# Data.Functor.Invariant

- Package
- purescript-invariant
- Repository
- purescript/purescript-invariant

### #Invariant Source

`class Invariant f where`

A type of functor that can be used to adapt the type of a wrapped function
where the parameterised type occurs in both the positive and negative
position, for example, `F (a -> a)`

.

An `Invariant`

instance should satisfy the following laws:

- Identity:
`imap id id = id`

- Composition:
`imap g1 g2 <<< imap f1 f2 = imap (g1 <<< f1) (f2 <<< g2)`

#### Members

`imap :: forall b a. (a -> b) -> (b -> a) -> f a -> f b`

#### Instances

- Modules
- Data.
Functor. Invariant