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A list of material that helped me learn the lens package.

Learning Lens

I tend to focus on core concepts quite a bit more than actual examples, so that the fundamental understanding of what the examples are trying to teach me is building on skills I already have just haven't figured out how to use yet.

tl;dr Your mileage may vary. I learn kind of counterintuitively for others.

Since this seemed to be popular, I decided to make a repository for content about haskell topics that you can find here new materials for lens will be put here

Presentations (40-70 minutes)

[SPJ talks about Lens] ( (Requires you to login, but is free to make an account)

This was one of the biggest influencers to me learning how lenses are supposed to operate.

[Creator Edward Kmett talks about Lenses, Folds, and Traversals] (

[The Unreasonable Effectiveness of Lenses for Business Applications] (

Great talk about how the various components of lens are used. Highly recommend this talk once you have a basic understanding of how lenses are meant to work.


[Lens over tea] (

Shows about how to build lenses up from nothing and why they are useful to the everyday programmer. (I need to finish this myself. Damn ADD)

[From Lenses to Yoneda Embedding] (

Talks about Comonads and how lenses fit into the whole big picture. Another one I really need to finish reading all the way through myself, but it does explain some (if not all) of the category theory behind lenses.

[Intolerable] (

Not really meant to be an introductory material, but it does provide a neat reference with examples for how the most used infix functions of Lens.

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