Generic Programming Made Easy in F# | Hacker News Reader

Generic Programming Made Easy in F#

demystifyfp.com

60 pointstamizh8813 comments

Read it twice, still not sure why simple type/tuple/record pattern matching was not enough. (https://docs.microsoft.com/en-us/dotnet/fsharp/language-refe...). Also active pattern matching could've solve exotic cases, if any (https://docs.microsoft.com/en-us/dotnet/fsharp/language-refe...)

saaame... A solution looking for a problem perhaps?

> if isGenTypeOf typedefof<_ option> then

Wow! This code looks horrible. Why don't you just accept the fact that the language is strongly typed and abolish reflection altogether?

I apologize for the tone of my comment, but still think that ML is not supposed to be written like that.

Agreed for ML. However, F# is not exactly ML. It lives on top of, and has to interoperate with, the existing .NET ecosystem.

That means, for example, that a lot of the datatypes you'll end up dealing with are object-oriented. Those can be difficult to work with in a generic way without resorting to reflection.

Sounds a bit like the Scala story: could be a really nice language, but the bagagge ... :)

It is a really nice language. Being able to interoperate with .NET is a strength, not a weakness. It's quite principled in its design, it's just that some of its design principles are pragmatic ones.

Concrete example: It doesn't have typeclasses. This was a deliberate and thoughtful move. The designers haven't been able to figure out how to implement type classes in a way that wouldn't interact poorly with the rest of the .NET ecosystem, so they've opted to keep them out rather than introducing a hacky implementation. Contrast this with Scala, where it's very easy to accidentally break compatibility with Java code when you're working with traits.

> Concrete example: It doesn't have typeclasses.

It's not like type classes are themselves suuuper-principled.

> Being able to interoperate with .NET is a strength, not a weakness.

Being able to interoperate with .NET is a good thing. Letting the .NET object model permeate the whole language's type structure is less of a good thing (to put it mildly). OCaml did the right thing w.r.t. objects: You can use objects if you so wish, but the language doesn't ram them down your throat.

F# and OCaml are different languages with different goals. It should come as no surprise there are different sacrifices between the languages.

Breaking compatibility with .NET, which is F#'s biggest benefit is counter productive.

My suggestion wouldn't “break compatibility” with .NET any more than, say, C++/CLI (or whatever it is called nowadays) does.

Wait it has https://docs.microsoft.com/en-us/dotnet/fsharp/language-refe...

Those are essentially ADTs --- not "type-classes" in the ML/Haskell/etc sense at all.

I think there is a frequent problem where blog posts are written by people who went down a rabbit hole they maybe shouldn't even be down.

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