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jtobin.io
Personal blog · jtobin.ioprogrammingmath
jtobin.io is a personal blog at jtobin.io about programming and math. Since 2019, 3 different Hacker News readers have linked it 3 times, most often “Kelvin Versioning”. It is still writing: the last post was on 2025-12-25, and you can follow it by feed.
Too few sampled comments (1) to say how often HN recommends it.?
Why HN links it
HN readers link this blog for a post explaining automatic differentiation as a catamorphism (a fold) over a function's syntax tree, tied to the chain rule and product-preserving functors.
Summarised by Claude from a sample of 1 HN comments that link here. Each comment is marked recommending, critical or neutral (citing without judging); how this works.
Most-linked posts?
- Kelvin Versioning2 people · 2 mentions · first linked 2022-04-07
What Hacker News says?
Differentiation (of functions) is a product-preserving functor, which makes the Chain Rule the rule by which it respects function composition, which makes automatic differentiation a matter of writing out the syntax tree of functions and "folding it up" via a catamorphism (a generalized fold). https://jtobin.io/ad-via-recursion-schemes Yes, really. I wasn't making that up. Automatic differentiation is a page or two…
Comment linking /ad-via-recursion-schemes
on “Applied Category Theory”Submitted Kelvin Versioning as a story · 2 points
HN discussionSubmitted Kelvin Versioning as a story · 1 points
HN discussion