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Type checking is a symptom, not a solution

(programmingsimplicity.substack.com)
67 points mpweiher | 3 comments | 05 Sep 25 05:56 UTC | HN request time: 0s | source
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toolslive ◴[05 Sep 25 19:30 UTC] No.45142651[source]▶
>functional programming languages ... break down when you try to coordinate between components, especially when those components are distributed ...

I think the exact opposite. Having spent more than a decade in distributed systems, I became convinced functional programming (and pure functions) are essential for survival in distributed systems.

Back then I wrote down my insights here (amazed that the site still exists)

https://incubaid.wordpress.com/2012/03/28/the-game-of-distri...

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1. zamalek ◴[05 Sep 25 19:49 UTC] No.45142848[source]▶
Even with my limited knowledge about FP I am pretty sure I would only grow more in agreement as I learn more. My only exposure to functional is via Nix and Rust (I promise I'll learn OCaml soon). One thing that I've really come to appreciate is the concept of "making invalid states unrepresentable," a trick that is harder than it should be (though not impossible) in "less functional" languages. Coming back to distributed systems, I have wondered what a functional database would look like. Mutations as pure functions, DUs in tuples, could we store a function, etc.
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2. toolslive ◴[05 Sep 25 20:02 UTC] No.45142971[source]▶
regarding databases, you get quite far using purely functional data structures and zippers.

- https://www.cs.cmu.edu/~rwh/students/okasaki.pdf

- https://en.wikibooks.org/wiki/Haskell/Zippers

3. addaon ◴[05 Sep 25 20:46 UTC] No.45143405[source]▶
> "making invalid states unrepresentable," a trick that is harder than it should be (though not impossible) in "less functional" languages

The flip side of this is to "make representable states valid." If you have an enum that doesn't fill a bitfield, values of the bitfield outside the enum are representable -- and the behavior of the system must be defined in that case. (Most often, this is done by mapping the behavior of undefined states to a chosen defined state, or using it to trigger an abort -- the key is that it must be an explicit choice.)