# Profunctor Equipment in Haskell

DevFeed: [Profunctor Equipment in Haskell](<https://devfeed.tech/articles/profunctor-equipment-in-haskell-28856.md>)

Original publisher: [Read original article](<https://bartoszmilewski.com/2026/05/16/profunctor-equipment-in-haskell/>)

Author: Bartosz Milewski

Published: 2026-05-16T09:47:40Z

Content type: tutorial

Language: en

Sources: [Bartosz Milewski's Programming Cafe](<https://devfeed.tech/sources/bartosz-milewski-s-programming-cafe.md>)

Topics: [Haskell](<https://devfeed.tech/topics/haskell.md>), [implementation](<https://devfeed.tech/topics/implementation.md>), [Code](<https://devfeed.tech/topics/code.md>), [Library](<https://devfeed.tech/topics/library.md>), [trust](<https://devfeed.tech/topics/trust.md>)

Tags: [category-theory](<https://devfeed.tech/tags/category-theory.md>), [code](<https://devfeed.tech/tags/code.md>), [compiler](<https://devfeed.tech/tags/compiler.md>), [haskell](<https://devfeed.tech/tags/haskell.md>), [implementation](<https://devfeed.tech/tags/implementation.md>), [library](<https://devfeed.tech/tags/library.md>), [profunctor-equipment](<https://devfeed.tech/tags/profunctor-equipment.md>), [profunctors](<https://devfeed.tech/tags/profunctors.md>), [programming](<https://devfeed.tech/tags/programming.md>), [standard-library](<https://devfeed.tech/tags/standard-library.md>), [types](<https://devfeed.tech/tags/types.md>)

## AI overview

This article presents a toy Haskell implementation of profunctor equipment. It explains how cells, composition, units, companions, and conjoints can be represented using standard library types, natural transformations, existential types, and profunctor composition, while noting limitations that would require dependent types.

## Source excerpt

Previously: Profunctor Equipment. To make things more palatable for programmers, I decided to provide a toy implementation of some of the equipments in Haskell. The advantage of this encoding is that it can be verified by the compiler, and I still trust the compiler more than I trust the AI. A more adequate implementation would [...]