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Comment by black_knight | Hacker News Reader

This is where I believe strong typing (like, Haskell-strong or stronger) and functional programming in general will be a win. The confidence I have that my fixes are localised when fixing Haskell code is infinitely stronger than fixing even Java, not speak about C, code.

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Haskell's type system would not easily prevent this bug. It's not good at numeric/logic issues like that. When people say "Haskell makes it impossible to write bugs" they mean "Haskell has enums" (ADTs).

I am not claiming you cant write buggy code in Haskell! But following good functional style, your bug will more likely be compartmentalised, and fixing it will not break some other part of your program.

You can write good functional code in many languages. (Even C++!)

Sure! I have done my fair share of pretending Java and C++ support my functional style. But at the end of the day, you have better support for writing that style in a real functional programming language. And I wonder how well one can enforce a functional style in say Java or C++ upon the LLMs. Who knows, they might be great at it?

Liquid Haskell might require you to prove that the divisor is nonzero, but even in standard Haskell there's common idioms for ensuring that a list is non-empty (data NonEmpty a = a :| [a]) or that text is non-empty (newtype NonEmptyText = NonEmptyText Text, with non-exported constructor, helpers like make :: Text -> NonEmptyText, or more advanced tricks like https://exploring-better-ways.bellroy.com/haskell-koan-type-... ).

The big problem preventing this approach from working for numbers is that it's just so cumbersome there. Most of this is because all the arithmetic operators are bundled into a single Num typeclass, and `fromInteger :: Num a => Integer -> a` has a type that's impossible for a "non-zero number" wrapper to satisfy.

OOP has those too, and they're very annoying.

In Haskell they are a little less annoying. It is just easier to reason about (including proving) pure functions.

I meant the constrained types by hiding the constructors. Super annoying, not automatically convertible, in Haskell you have to remember what the fake constructor is called, and write it every time you use it, but at least it's efficiently implemented with newtype, unlike the Java OOP version. Think about writing a value with several nested constrained types, like NonEmptyListOne (makeNonZeroNumber 42, 'h' `NonEmptyString` "ello world"). It's just really annoying.

The blog link I mentioned avoids this cost with literals, by providing using a required type argument to check the string length at compile time without TH. It requires a relatively recent GHC:

    make :: forall symbol -> (IsNonEmptySymbol symbol) => NonEmptyText

    type family IsNonEmptySymbol symbol :: Constraint where
      IsNonEmptySymbol "" = Unsatisfiable (Text "Expected a non-empty string")
      IsNonEmptySymbol _ = (()::Constraint) -- empty constraint is always satisfied

Definitely room for improvement on Haskell's standard library when it comes to the number-related type classes. Modern Haskell could do very well in this area with a good type-class redesign in this area. The issue I think is that this would invalidate a lot of existing code, relying upon that. But you can already replace Prelude with something else in your own code if you want to.

I think Idris has a better chance there.

People don’t say "Haskell makes it impossible to write bugs"! You may have heard "if it compiles it works" which is somewhat tongue in cheek, but also true for a sufficiently loose interpretation of "works" in a way it is not true for languages with a less strong and flexible type system.

You haven't mentioned the dynamic typed languages that I believe should die -- Python and Javascript. The only good use case for dynamic typing is notebooks (niche of R lang) where you're throwing out the code you just wrote after getting the result you wanted from it.

Imo, formal methods like more expressive/stricter type systems are key to making LLM generated code successful. Of course models will get better, but trusting the output will become much easier with a type system that proves more properties.

What's stronger than Haskell?

Perhaps coq/agda/idris/etc.

Anything with ranged numeric types. Like everyone's favorite functional programming language, Ada.

Or Liquid Haskell.

This issue raises SIGFPE. Ada would raise Constraint_error, which is easier to catch than a signal, but still occurs at runtime.

You need range proofs to be 100% safe, and then you can as well use the regular type because invalid values will not occur.

Dependent types is one possible direction. Not sure when a language with dependent types will arise which will be useful for making real programs.

Agda is the most mature dependently typed programming languae (having been around since the 90s – it is basically Haskell on steroids), but has a more proof-assistant flavor than an actual programming language flavor. Opus & Fable write Agda quite well, so LLMs can understand dependent types.

Lean 4, Idris 2.

Even Lean 4 strong typing

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