BSD-3-Clause licensed by Eitan Chatav
Maintained by [email protected]
This version can be pinned in stack with:free-categories-,732

Module documentation for

Depends on 1 package(full list with versions):


Consider the category of Haskell “quivers” with

  • objects are types of higher kind
    • p :: k -> k -> Type
  • morphisms are terms of RankNType,
    • forall x y. p x y -> q x y
  • identity is id
  • composition is .

Now, consider the subcategory of Haskell Categorys with

  • constrained objects Category c => c
  • morphisms act functorially
    • t :: (Category c, Category d) => c x y -> d x y
    • t id = id
    • t (g . f) = t g . t f

The free category functor from quivers to Categorys may be defined up to isomorphism as

  • the functor Path of type-aligned lists

  • the functor FoldPath of categorical folds

  • abstractly as CFree path => path, the class of left adjoints to the functor which forgets the constraint on Category c => c

  • or as any isomorphic data structure


Revision history for free-categories – 2019-10-01

  • First version.