Functor Fact

Functional programming and category theory tweets from @JohnDCook

[Functor Fact @FunctorFact]

The groups in the category of groups are the Abelian groups!

[Functor Fact @FunctorFact]

A group 'in a category' is not the same thing as the category of groups. You can have groups in any category that has products.

[Functor Fact @FunctorFact]

In the category of groups, direct products are products, free products are coproducts.

[Functor Fact @FunctorFact]

Interesting categories are big https://t.co/uw8bLkWyAt

[Functor Fact @FunctorFact]

Hy: A Lisp that transforms to the Python abstract syntax tree https://t.co/Q8TfKlL7VV

[Functor Fact @FunctorFact]

'Theorems for Free' and related papers by Philip Wadler https://t.co/S6Xmgjukrm

[Functor Fact @FunctorFact]

'Coconut is a simple, elegant, Pythonic functional programming language that compiles to Python.' https://t.co/3231GxK5FU

[Functor Fact @FunctorFact]

Epic and monic https://t.co/7xV4c8JStq

[Functor Fact @FunctorFact]

A functor between two categories maps objects to objects and morphisms to morphisms in a structure-preserving way.

[Functor Fact @FunctorFact]

'This may be one of the gentlest introductions to the idea of categories and monads that you will find.' https://t.co/LAdRYjRcQo

[Algebra Etc. @AlgebraFact]

Categorical models of logics
https://t.co/LgDD8pdBCn

[Louis Maddox @permutans]

📄 Spivak (2026) Compositional Dynamics in Learning and Mechanics https://t.co/L6Its4oWQy

[Functor Fact @FunctorFact]

starring Denzel Washington

[Functor Fact @FunctorFact]

Don't fear the monad https://t.co/zXiT7YeyQE by @lorentzframe

[Functor Fact @FunctorFact]

The 'range' of a function f: A -> B is ambiguous. Some use the term to mean the codomain B and others to mean the image f(A).

[Functor Fact @FunctorFact]

A general theory of sub-things https://t.co/BCBR0LmS3I

[Functor Fact @FunctorFact]

'Category theory has been called 'abstract nonsense' both by its friends and its detractors.' -- Joseph Goguen

[Functor Fact @FunctorFact]

Co-limits in category theory are also called direct limits, inductive limits, and right roots.

[Functor Fact @FunctorFact]

Limits in category theory are also called inverse limits, projective limits, and left roots.