#gadt — Public Fediverse posts

Oh nice. Just found 2 #rustlang nightly features which look like they might bring us closer to one of the two major type level things Iam missing hard in #rust : "extistenia types" (the other one are #GADT)

type_alias_impl_trait:
https://doc.rust-lang.org/unstable-book/language-features/type-alias-impl-trait.html

impl_trait_in_assoc_type:
https://doc.rust-lang.org/nightly/unstable-book/language-features/impl-trait-in-assoc-type.html

Red-black tree in Lean 4 prover.

I proved all needed properties, for example that resulting tree is sorted.

I implemented one operation only: insertion. And I "cheat" by assuming that original tree is always black. My goal was not implementing everything, I just wanted to implement one simple operation and prove really everything about it.

Proof of sorting (insert_sorted) turned out to be rather big. If someone knows how to make it smaller (possibly using mathlib), then, please, tell me that.

https://rentry.co/8sfon8ez

#types.pl #lean #plt #gadt

https://react-book.melange.re/intro/
I love #ocalm.

it has many superpowers
- #soundcomplete and #strong #typesystem with #typeinference

- #algebraiceffects
- #algebraicdatatypes
- #GADT
- #patternmatching
- pragmatic by default #immutanbility
- pragmatic and optional laziness
it gives confidence and correctness via type system and compiles
#ocaml shape languages like #scala and #rust also #Fsharp is just reincarnation of ocaml for dotnet
Melange brings this power to #reactnative developers.

🇫🇷 L'année passée, j'ai décris un usage du GADT `Eq` pour implémenter des méthodes gardées (et résoudre les méthodes `sum`, `prod` et `flatten`) en préservant la sémantique d'envoi de message !

https://xvw.lol/pages/oop-refl.html

N'hésitez pas à me faire des retours !
#ocaml #gadt #oop

It seems one can represent ZFC (or any other logic or type system) as Lean 3's GADT. Note that binder very elegantly represented as HOAS. Am I first who discovered this? #types.pl #plt #lean #lean3 #gadt #zfc #hoas

https://lobste.rs/s/11k4ri/how_should_i_read_type_system_notation#c_rtpme5

Implémenter des méthodes gardées en OCaml avec un témoin d'égalité explicite, un article de @xvw https://xvw.github.io/capsule/pages/oop-refl.html #OCaml #OOP #GADT

#GADT #OCaml - https://gist.github.com/dinosaure/fab7979030d3325f2c8ddc02ab5e7646