schema VS immer

Plumatic schema (https://github.com/plumatic/schema) , or friends I might be wrong, but I think schema might make more sense to you coming from the F# world (might be wrong)

This one? I didn't. I hear good things about it, and it's reached a point of maturity, being widely used in production.

Uhhh spec has existed for a long time and before that, schema Nowadays we also have the excellent malli. If his codebase is full of functions where the shape of the data isn’t obvious, isn’t documented and isn’t specified in a specific/schema, that’s on him and his bad coding practices and really no different from passing data in other dynamic languages. A class by itself (without additional effort) only gives you field names.

I don't understand this reputation either. There are very large systems built on other Lisps. For example, Emacs has a massive amount of Elisp. Elisp is much more primitive than Clojure, and traditionally libraries don't use e.g. data schemas [1] as runtime contracts for data.

Obviously, once a system built on top of a dynamic language grows beyond certain threshold, you need to be very disciplined as there are no static types to ensure some degree of correctness.

[1] https://github.com/plumatic/schema

Try to learn a schema library early, like Malli or Prismatic Schema. Do not mistook them as "static-typing" things - it's more for data validation and coercion than "security that things will get the right typing information". The idea to learn them early is how you'll shape future code: validating all "output data" first, them using that data inside your program without "defensive programming" like checking every time if a specific value on a map is nil, etc

In Clojure, declarative data specifications for validation and generation are also very mainstream. Schema was first out the door, Clojure Spec is the most popular library, while malli is gaining popularity fast at the moment.

I've been working on an editor (not text) in C++ and pretty early got into undo/redo. I went down the route of doIt/undoIt for commands but that quickly got old. There was both the extra work needed to implement undo separately for every operation, but also the nagging feeling that the undo operation for some operation wasn't implemented correctly.

In the end, I switched to representing the entire document state using persistent data structures (using the immer library). This vastly simplified things and implementing undo/redo becomes absolutely trivial when using persistent data structures. It's probably not something that is suitable for all domains, but worth checking out.

https://github.com/arximboldi/immer

How does this compare to https://github.com/arximboldi/immer (other than the C/C++ difference)?

Also, it's my understanding that, in practice, persistent data structures require a garbage collector in order to handle deallocation when used in a general-purpose way. How does your implementation handle that?

You might be interested in ewig and immer by Juan Pedro Bolivar Puente:

https://github.com/arximboldi/ewig

https://github.com/arximboldi/immer

See the author instantly opening a ~1GB text file with async loading, paging through, copying/pasting, and undoing/redoing in their prototype “ewig” text editor about 27 minutes into their talk here:

https://m.youtube.com/watch?v=sPhpelUfu8Q

It’s backed by a “vector of vectors” data structure called a relaxed radix balanced tree:

https://infoscience.epfl.ch/record/169879/files/RMTrees.pdf

That original paper has seen lots of attention and attempts at performance improvements, such as:

https://hypirion.com/musings/thesis

https://github.com/hyPiRion/c-rrb

You’re absolutely right, however people have been putting in the “extra efforts” required for efficiency. Check out immer if you’re interested.

The C++ immer library: https://github.com/arximboldi/immer

For C++ check this one out - https://github.com/arximboldi/immer

Yeah I agree that I should link that wikipedia page in the docs, I'll do that as soon as I get a chance. immer (https://github.com/arximboldi/immer) also links that page in its docs, for the exact same reason I'm sure. Interestingly, there is a lot of overlap between persistent data structures in the functional programming sense and persistent data structures in the persisted-to-disk sense because persistent data structures in the FP sense are one of the best ways to guarantee atomic updates and safe failure recovery in a persisted-to-disk system! Btrfs and ZFS, as well as many databases, are at their core basically just copy-on-write B+ trees.

I’ve never tried it, but I love the idea of implementing editor scene state using immutable data structures like https://github.com/arximboldi/immer With that, every edit would append a new node to a list of scene states. Undo/redo becomes iterating your view of the scene up and down through that list. Can’t screw up an undo function if there’s never any work to do :P

I have! I think it's related to the C++ immer library which I used several years ago in Vortex. It's kinda like the previous generation of ValueScript. 🍻