Programming Languages

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Hello!

This is the current Lemmy equivalent of https://www.reddit.com/r/ProgrammingLanguages/.

The content and rules are the same here as they are over there. Taken directly from the /r/ProgrammingLanguages overview:

This community is dedicated to the theory, design and implementation of programming languages.

Be nice to each other. Flame wars and rants are not welcomed. Please also put some effort into your post.

This isn't the right place to ask questions such as "What language should I use for X", "what language should I learn", and "what's your favorite language". Such questions should be posted in /c/learn_programming or /c/programming.

This is the right place for posts like the following:

"Check out this new language I've been working on!"
"Here's a blog post on how I implemented static type checking into this compiler"
"I want to write a compiler, where do I start?"
"How does the Java compiler work? How does it handle forward declarations/imports/targeting multiple platforms/?"
"How should I test my compiler? How are other compilers and interpreters like gcc, Java, and python tested?"
"What are the pros/cons of ?"
"Compare and contrast vs. "
"Confused about the semantics of this language"
"Proceedings from PLDI / OOPSLA / ICFP / "

See /r/ProgrammingLanguages for specific examples

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armchair_progamer@programming.dev

Lean Programming Language - with formally verified code (lean-lang.org)

submitted 3 days ago* (last edited 3 days ago) by Kissaki@programming.dev to c/programming_languages@programming.dev

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Lean is a theorem prover and programming language that enables correct, maintainable, and formally verified code

/-- A prime is a number larger than 1 with no trivial divisors -/
def IsPrime (n : Nat) := 1 < n ∧ ∀ k, 1 < k → k < n → ¬ k ∣ n

-- 'Grind' efficiently manages complex pattern matching and
-- case analysis beyond standard tactics.
example (x : Nat) : 0 < match x with
  | 0   => 1
  | n+1 => x + n := by
  grind

-- Automatically solves systems of linear inequalities.
example (x y : Int) :
    27 ≤ 11*x + 13*y → 11*x + 13*y ≤ 45
    → -10 ≤ 7*x - 9*y → 7*x - 9*y > 4 := by
  grind

Does anyone have experience with Lean? Can it be useful for implementing algorithms or logic beyond mathematical proofs, for software libs?

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[–] mobotsar@sh.itjust.works 3 points 2 days ago* (last edited 2 days ago)

I've used Lean 4 a decent amount. It's quite usable for writing normal software in the way you would write Haskell. I find it nicer than Haskell, frankly; more predictable. It's even pretty easy to model ocaml/sml modules, roughly. There's an ever-present temptation to lean into using advanced type theory in ways you couldn't in those simpler languages, and which will complicate your design and make the programming quite a bit more challenging as it goes on, but you don't have to give in to temptation.

[–] FizzyOrange@programming.dev 4 points 3 days ago (1 children)

Yeah you can use it for normal software. It is very complex though, and the documentation assumes you already have a PhD in formal verification.

[–] mobotsar@sh.itjust.works 1 points 2 days ago

assumes you already have a PhD in formal verification

I wouldn't go that far. I don't have a PhD in anything, and I find it pretty comprehensible for the most part. I did focus on formal logic for my undergrad computer science degree, but that's my only formal training, and I'm not some genius or anything approaching that.

[–] anton@lemmy.blahaj.zone 3 points 3 days ago

The comment in the first example is wrong, it should be no nontrivial divisors.
Quite ironic, that they can prove theorems about their code, but the comments can't be checkt by the compiler, resulting in their first math example being wrongly described.

[–] gratux@lemmy.blahaj.zone 4 points 3 days ago

I haven't tried Lean, but one of my university courses had us use Dafny, which essentially states the pre- and postcondition of a function. If it can't prove the conditions are fulfilled, you get an error. This essentially turns all of your bugs (that is, unexpected behaviour) into specification problems. It can also prove that loops eventually end, and the data in a structure follows a specific pattern.