
Control.Functor  Portability  portable  Stability  experimental  Maintainer  dan.doel@gmail.com 





Description 
Functor composition, standard functors, and more.


Synopsis 




Unary functors


Composition



Functor composition.
(Note: Some compilers will let you write f `O` g rather than O f g;
we'll be doing so here for readability.)
Functor composition is associative, so f `O` (g `O` h) and (f `O` g) `O` h
are equivalent. The functions lComp and rComp convert between the two.
(Operationally, they are equivalent to id. Their only purpose is to affect
the type system.)
 Constructors   Instances  






Basic Instances


Unit



The unit functor.
(Note: this is not the same as (). In fact, Unit is the
fixpoint of ().)
 Constructors   Instances  


Const



Constant functors. Essentially the same as Unit, except that they also
carry a value.
 Constructors   Instances  


Binary functors



A type constructor which takes two arguments and an associated map function.
Informally, Bifunctor f implies Functor (f a) with fmap = bimap id.
  Methods  bimap :: (a > c) > (b > d) > f a b > f c d  Source 

  Instances  


Trinary functors


class Trifunctor f where  Source 

A type constructor which takes three arguments and an associated map function.
Informally, Trifunctor f implies Bifunctor (f a) with bimap = trimap id.
  Methods  trimap :: (a > a') > (b > b') > (c > c') > f a b c > f a' b' c'  Source 

  Instances  


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