Advent Of Code

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An unofficial home for the advent of code community on programming.dev!

Advent of Code is an annual Advent calendar of small programming puzzles for a variety of skill sets and skill levels that can be solved in any programming language you like.

AoC 2024

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🪐 - 2024 DAY 11 SOLUTIONS -🪐 (programming.dev)

submitted 2 weeks ago by [email protected] to c/[email protected]

30 comments fedilink hide all child comments

Day 11: Plutonian Pebbles

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[–] [email protected] 2 points 2 weeks ago (1 children)

Does the IORef go upwards the recursion tree? If you modify the IORef at some depth of 15, does the calling function also receive the update, is there also a Non-IO-Ref?

[–] [email protected] 2 points 2 weeks ago* (last edited 2 weeks ago)

The IORef is like a mutable box you can stick things in, so readIORef returns whatever was last put in it (in this case using modifyIORef'). "last" makes sense here because operations are sequenced thanks to the IO monad, so yes: values get carried back up the tree to the caller. There's also STRef for the ST monad, or I could have used the State monad which (kind of) encapsulates a single ref.