Comment by gwbas1c

Comment by gwbas1c 3 days ago

If you've had C# and F# co-exist in the same codebase, how do they co-exist? Is it like C# and VB.Net where a project (dll) is either C# or VB.Net, and they can reference each other?

Or: Is it more like the Swift / Objective C ecosystem where Swift, Objective C, and even straight C can co-exist in the same library?

In a mixed C# and F# codebase, generally when do you favor C# versus F#?

Coming from a C# background, what are the areas where F# is a better language?

Any success stories for F#, especially if it co-exists with C#? Any horror stories?

neonsunset 3 days ago

You have likely heard "functional core, imperative shell". This refers to having IO-heavy code that favors imperative patterns be written in C# and then have the actual domain logic core written in F# which is much better at expressing it. Because both languages are hosted on .NET, you simply achieve it by having two projects and having one reference another. It is very seamless F# and C# types are visible to each other if marked to be so.

The biggest advantage of F# is its gradual typing and full type inference which allows to massively reduce the amount of text required to describe application or domain logic. It is also extremely composable and I find doing async in F# somewhat nicer than in C# too. F# also has better nullability (or, rather, lack of thereof) assurances and, in my opinion, better UX for records.

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gwbas1c 3 days ago

That's just like how C# and VB.Net can co-exist in the same project. Would you pick the pattern of:
1: C# Library with interfaces and/or abstract base classes
2: F# library with implementations of those interfaces and base classes
3: C# program (console, web service, GUI, ect) that specifies the implementations in Dependency Injection
Or is there a simpler way for C# and F# to co-exist in the same project (dll or exe)?

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- int_19h 3 days ago
  
  You don't really need to split 1 & 2, since F# can define .NET interfaces and abstract classes just fine.
  For that matter, you don't even need the interfaces if you wouldn't have had them in a C#-only solution. Just define the class in F# and use it directly from C#.
  You still need a separate assembly for F#, but that doesn't imply dependency injection - again, just reference it and use it.
  
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  gwbas1c 2 days ago
  
  I've identified a possible use case for F# in a preexisting product; I'm looking for the simplest way to integrate F#.
  
  Reply View | 2 replies

debugnik 3 days ago

Yes mixing is just like with VB.NET.

When mixing, you often write business logic as self-contained F# libraries with a C#-friendly API; and use C# to integrate them with whatever imperative, reflection-heavy and DI-heavy frameworks .NET is promoting the current year, since those are filled with interop edge cases for F# anyway.

You really want to avoid a language sandwich though (e.g. C#/F#/C#), because you'll keep wishing to remove the middle layer. Sadly, the addition of source generators make this mistake even more appealing.

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