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OCaml does not require more annotations than Haskell for polymorphic functions? Both language only require annotations in the case where inference would be unde

OCaml does not require more annotations than Haskell for polymorphic functions? Both language only require annotations in the case where inference would be undecidable (polymorphic recursions, higher-rank polymorphism, and GADTs). I know few cases where OCaml require less annotations than Haskell, I would expect the reverse to be true. And maps and sets are not the main use case for polymorphism in OCaml. Even taking in account that it sounds like you are talking about functors, maps and sets are still not the only instance of functors in OCaml.

wyager 4y ago
> OCaml does not require more annotations than Haskell for polymorphic functions? A) I am fairly confident this is not actually true in a technical sense, although it's been several years since I've thought about it B) In any case, in the (many) instances where you (by rule or convention) need to put a type signature on your function (e.g. because it's a top-level function, one that you export, etc.), it is a pain in the ass to make it polymorphic in ocaml compared to in haskell. > Even taking in account that it sounds like you are talking about functors No, I'm not, although ocaml people tend to think exclusively in "functors" (badly named, in my opinion - conflicts with the more common category-theoretic definition) because the experience of using actually parametric functions is so bad that they almost never do it.
- octachron 4y ago
  Do you have any examples? Unfortunately from my perspective, I cannot make sense of your statements. OCaml typing is principal in all situation where type inference is decidable. The syntax for annotation for polymorphic functions is isomorphic between OCaml and Haskell. If I take a random module in the standard library, let's say Array, 95% of the functions in this module are parametric polymorphic. I am thus genuinely puzzled by your statement that "OCaml programmers almost never write polymorphic functions".
  - wyager 4y ago
    I wrote up a bunch of grievance examples for a blog post I never got around to publishing, but I'm traveling at the moment so can't pull up my laptop. I'll see if I can find them later. > The syntax for annotation for polymorphic functions is isomorphic between OCaml and Haskell. Sorry, but total bullshit. I had to use these pieces of shit all the time. https://v2.ocaml.org/manual/locallyabstract.html https://v2.ocaml.org/manual/locallyabstract.html > If I take a random module in the standard library, let's say Array As I specifically called out, all the core data structures are polymorphic. (Let's not talk about the float array hack; is that still around?) It's so annoying that pretty much every other library is monomorphic or functorized. > I am thus genuinely puzzled by your statement that "OCaml programmers almost never write polymorphic functions". Not sure what to tell you man. I spent 4 years reading & writing ocaml and 95% of the code that would have been polymorphic in haskell (because it would be easy/free) was either monomorphic or (multiple layers of) functors. Many/most of the devs I worked with (great devs with years of OCaml experience) didn't even know what LATs were, let alone used them, which means they were almost certainly not writing polymorphic code which "did anything" with the type. The only polymorphic code that you can write in ocaml without such things are functorial (in the categorical sense, not the ocaml sense). Arrays, map values, that's about it.
    - octachron 4y ago
      > Sorry, but total bullshit. Ok, locally abstract types are bit weird and historical quirk due to the pre-existing use of type variables as unification type variables. But first, they only matter with GADTs and local modules (a notion that doesn't exist in Haskell). And the good syntax for polymorphic function with GADTs is `type a. a monoid -> a` which requires just one explicit quantification compared to the Haskell variant. So no, Haskell and OCaml type annotations are isomorphic. > As I specifically called out, all the core data structures are polymorphic. I took a totally random module from the standard library! Let me another random module after rolling a dice, Atomic. Here only 66% of the functions are polymorphics. Or do you want me to go to another library? Ok, let's go for container, and let's select another random module CCPair: 100% of the functions are polymorphic. Honestly, I struggle to understand how it is possible to conclude that every OCaml library is monomorphic. What do you mean by LATs? The Haskell wiki doesn't seem to know that term. > The only polymorphic code that you can write in ocaml without such things are functorial I am sorry to ask but are you confusing bounded polymorphism with parametric polymorphism?

wyager 4y ago

> OCaml does not require more annotations than Haskell for polymorphic functions? A) I am fairly confident this is not actually true in a technical sense, although it's been several years since I've thought about it B) In any case, in the (many) instances where you (by rule or convention) need to put a type signature on your function (e.g. because it's a top-level function, one that you export, etc.), it is a pain in the ass to make it polymorphic in ocaml compared to in haskell. > Even taking in account that it sounds like you are talking about functors No, I'm not, although ocaml people tend to think exclusively in "functors" (badly named, in my opinion - conflicts with the more common category-theoretic definition) because the experience of using actually parametric functions is so bad that they almost never do it.

octachron 4y ago
Do you have any examples? Unfortunately from my perspective, I cannot make sense of your statements. OCaml typing is principal in all situation where type inference is decidable. The syntax for annotation for polymorphic functions is isomorphic between OCaml and Haskell. If I take a random module in the standard library, let's say Array, 95% of the functions in this module are parametric polymorphic. I am thus genuinely puzzled by your statement that "OCaml programmers almost never write polymorphic functions".
- wyager 4y ago
  I wrote up a bunch of grievance examples for a blog post I never got around to publishing, but I'm traveling at the moment so can't pull up my laptop. I'll see if I can find them later. > The syntax for annotation for polymorphic functions is isomorphic between OCaml and Haskell. Sorry, but total bullshit. I had to use these pieces of shit all the time. https://v2.ocaml.org/manual/locallyabstract.html https://v2.ocaml.org/manual/locallyabstract.html > If I take a random module in the standard library, let's say Array As I specifically called out, all the core data structures are polymorphic. (Let's not talk about the float array hack; is that still around?) It's so annoying that pretty much every other library is monomorphic or functorized. > I am thus genuinely puzzled by your statement that "OCaml programmers almost never write polymorphic functions". Not sure what to tell you man. I spent 4 years reading & writing ocaml and 95% of the code that would have been polymorphic in haskell (because it would be easy/free) was either monomorphic or (multiple layers of) functors. Many/most of the devs I worked with (great devs with years of OCaml experience) didn't even know what LATs were, let alone used them, which means they were almost certainly not writing polymorphic code which "did anything" with the type. The only polymorphic code that you can write in ocaml without such things are functorial (in the categorical sense, not the ocaml sense). Arrays, map values, that's about it.
  - octachron 4y ago
    > Sorry, but total bullshit. Ok, locally abstract types are bit weird and historical quirk due to the pre-existing use of type variables as unification type variables. But first, they only matter with GADTs and local modules (a notion that doesn't exist in Haskell). And the good syntax for polymorphic function with GADTs is `type a. a monoid -> a` which requires just one explicit quantification compared to the Haskell variant. So no, Haskell and OCaml type annotations are isomorphic. > As I specifically called out, all the core data structures are polymorphic. I took a totally random module from the standard library! Let me another random module after rolling a dice, Atomic. Here only 66% of the functions are polymorphics. Or do you want me to go to another library? Ok, let's go for container, and let's select another random module CCPair: 100% of the functions are polymorphic. Honestly, I struggle to understand how it is possible to conclude that every OCaml library is monomorphic. What do you mean by LATs? The Haskell wiki doesn't seem to know that term. > The only polymorphic code that you can write in ocaml without such things are functorial I am sorry to ask but are you confusing bounded polymorphism with parametric polymorphism?