Ancestors

Written by CameronDev@programming.dev on 2024-12-24 at 06:00

🤖 - 2024 DAY 24 SOLUTIONS - 🤖

https://programming.dev/post/23243817

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Written by gedhrel@lemmy.world on 2024-12-24 at 11:58

Haskell bits and pieces

The nice thing about Haskell’s laziness (assuming you use Data.Map rather than Data.Map.Strict) is that the laziness can do a ton of the work for you - you might’ve spotted a few Haskell solutions in earlier days’ threads that use this kind of trick (eg for tabling/memoisation). Here’s my evaluation function:

let

v = l & Map.map (\case

                   Const x -> x

                   And a b -> v Map.! a && v Map.! b

                   Or a b  -> v Map.! a || v Map.! b

                   Xor a b -> v Map.! a /= v Map.! b)

in v

For part 2, we know what the graph should look like (it’s just a binary adder); I think this is a maximal common subgraph problem, but I’m still reading around that at the mo. I’d love to know if there’s a trick to this.

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Written by VegOwOtenks@lemmy.world on 2024-12-24 at 12:44

Thank you for showing this trick, I knew Haskell was lazy but this one blew my mind again.

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Toot

Written by gedhrel@lemmy.world on 2024-12-24 at 13:34

Yeah, I remember when I saw this for the first time. It’s astonishing how powerful lazy evaluation can be at times.

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