Lenses, Folds, and Traversals
Why Hacker News recommends it
HN calls it dense but mind-blowing, the go-to way to understand lenses through algebraic derivation.
What it is
Edward Kmett's talk to the NY Haskell User Group on the lens library, building from fmap and function composition up to lenses, folds and traversals. It shows how these composable combinators access and modify parts of data structures.
Recommended by 3 HN commenters across 3 different months, 2013 to 2014.
What Hacker News said
Strong rec mijoharas · 2014-11 · on “How I Start: Haskell”
I found this talk by edward kmett incredibly helpful[0]. I kept rewatching parts of it bit by bit until I managed to absorb it all (there is a lot of information for a beginner) but I found it hugely helpful and mind-blowingly powerful. [0] [this video]
Recommends jerf · 2013-01 · on “Why is the C++ STL so heavily based on templates?”
If you want to work in an environment where a lot of people are thinking like this routinely, instead of a few lone voices in a vast sea of otherwise uninterested people, the Haskell community is doing a lot of work in this area, and able to move much faster since it's so much easier in Haskell than C++ templates (which isn't really a criticism of C++ templates, a lot of their capabilities are accidental rather than intended). This is why the Haskell community talks so much about monoids and applicatives and semigroups and a variety of other interesting structures in that area (and no, I did not forget to say monad, that structure is actually uninteresting here because it is too powerful). I
Recommends dllthomas · 2014-08 · on “Letter to a Young Haskell Enthusiast”
"The best forms of language advocacy probably involve showing the great things you've done with a language and forgetting about comparisons to the competition." Great things the parent has done with the language: [this video]