this post was submitted on 19 Aug 2023
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Using exceptions in C++ desktop and server applications overall made sense to me. As I expanded my usage of C++ into other domains, specifically embedded domains, I began to experience more compelling reasons not to use exceptions first-hand...

From lobste.rs

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[–] [email protected] -1 points 1 year ago (2 children)

I think that pattern matching and sum types are orthogonal to monads, and aren't really relevant when discussing monads as alternatives to exceptions. C++ didn't required any of those to add std::optional or std::variant, and those are already used as result monads.

Supporting Result and Either monads in the standard would be nice, but again this does not stop anyone from adopting one of the many libraries that already provide those.

[–] [email protected] 3 points 1 year ago (1 children)

Well, if you create result types without monads, you get go.

I would say it's completely essential, but you can do with some limited implementation of them.

[–] [email protected] 3 points 1 year ago

I guess it depends on what you mean by using monads, but you can have a monadic result type without introducing a concrete monad abstraction that it implements.

[–] [email protected] 2 points 1 year ago (1 children)

You seem to be ignoring the benefits of compiler support as mentioned in the comment above.

[–] [email protected] 1 points 1 year ago* (last edited 1 year ago) (1 children)

compiler support

That remark was on sum types, not monads. You do not need "compiler support" to have Result or neither monads in C++. There are already plenty of libraries that implement those. I use them in some of my projects. No compiler support needed.

As I said, sum types are not required for Return or Either monads. At best, they are convenient.

[–] [email protected] 1 points 1 year ago (1 children)

The original claim wasn't that you can't implement monads in C++, it was that compiler support is needed for "good" sum types. Unless I'm misreading, you brought monads into it. And they're not totally orthogonal: sum types are a very good way to implement monads.

[–] [email protected] 1 points 1 year ago* (last edited 1 year ago) (1 children)

Unless I’m misreading, you brought monads into it.

You're misreading it. What do you think a 'Result' type is?

[–] [email protected] 1 points 1 year ago (1 children)

Well, in Rust, it's a sum-type, with functions that also let you use it like a monad instead of using explicit pattern matching.

[–] [email protected] 1 points 1 year ago* (last edited 1 year ago) (1 children)

Well, in Rust, it’s a sum-type

The discussion is on to use monads in C++, and not on why is C++ different than Rust.

I repeat: you do not need sum types to implement a Result monad in C++.

[–] [email protected] 1 points 1 year ago

The discussion was about sum types. The top-level comment, the one to which you originally responded, says:

It's a shame that sum type support is still so lacking in C++. Proper Result types (ala Haskell or Rust) are generally much nicer to deal with, especially in embedded contexts.