What are the benefits of using C# vs F# or F# vs C#? [closed]

Question

General benefits of functional programming over imperative languages:

You can formulate many problems much easier, closer to their definition and more concise in a functional programming language like F# and your code is less error-prone (immutability, more powerful type system, intuitive recurive algorithms). You can code what you mean instead of what the computer wants you to say ;-) You will find many discussions like this when you google it or even search for it at SO.

Special F#-advantages:

• Asynchronous programming is extremely easy and intuitive with async {}-expressions - Even with ParallelFX, the corresponding C#-code is much bigger

• Very easy integration of compiler compilers and domain-specific languages

• Extending the language as you need it: LOP

• Units of measure

• More flexible syntax

• Often shorter and more elegant solutions

Take a look at this document

The advantages of C# are that it's often more accurate to "imperative"-applications (User-interface, imperative algorithms) than a functional programming language, that the .NET-Framework it uses is designed imperatively and that it's more widespread.

Furthermore you can have F# and C# together in one solution, so you can combine the benefits of both languages and use them where they're needed.

It's like asking what's the benefit of a hammer over a screwdriver. At an extremely high level, both do essentially the same thing, but at the implementation level it's important to select the optimal tool for what you're trying to accomplish. There are tasks that are difficult and time-consuming in c# but easy in f# - like trying to pound a nail with a screwdriver. You can do it, for sure - it's just not ideal.

Data manipulation is one example I can personally point to where f# really shines and c# can potentially be unwieldy. On the flip side, I'd say (generally speaking) complex stateful UI is easier in OO (c#) than functional (f#). (There would probably be some people who disagree with this since it's "cool" right now to "prove" how easy it is to do anything in F#, but I stand by it). There are countless others.

• F# Has Better Performance than C# in Math
• You could use F# projects in the same solution with C# (and call from one to another)
• F# is really good for complex algorithmic programming, financial and scientific applications
• F# logically is really good for the parallel execution (it is easier to make F# code execute on parallel cores, than C#)

To answer your question as I understand it: Why use C#? (You say you're already sold on F#.)

First off. It's not just "functional versus OO". It's "Functional+OO versus OO". C#'s functional features are pretty rudimentary. F#'s are not. Meanwhile, F# does almost all of C#'s OO features. For the most part, F# ends up as a superset of C#'s functionality.

However, there are a few cases where F# might not be the best choice:

• Interop. There are plenty of libraries that just aren't going to be too comfortable from F#. Maybe they exploit certain C# OO things that F# doesn't do the same, or perhaps they rely on internals of the C# compiler. For example, Expression. While you can easily turn an F# quotation into an Expression, the result is not always exactly what C# would create. Certain libraries have a problem with this.

  • Yes, interop is a pretty big net and can result in a bit of friction with some libraries.

  • I consider interop to also include if you have a large existing codebase. It might not make sense to just start writing parts in F#.

• Design tools. F# doesn't have any. Does not mean it couldn't have any, but just right now you can't whip up a WinForms app with F# codebehind. Even where it is supported, like in ASPX pages, you don't currently get IntelliSense. So, you need to carefully consider where your boundaries will be for generated code. On a really tiny project that almost exclusively uses the various designers, it might not be worth it to use F# for the "glue" or logic. On larger projects, this might become less of an issue.

  • This isn't an intrinsic problem. Unlike the Rex M's answer, I don't see anything intrinsic about C# or F# that make them better to do a UI with lots of mutable fields. Maybe he was referring to the extra overhead of having to write "mutable" and using <- instead of =.

  • Also depends on the library/designer used. We love using ASP.NET MVC with F# for all the controllers, then a C# web project to get the ASPX designers. We mix the actual ASPX "code inline" between C# and F#, depending on what we need on that page. (IntelliSense versus F# types.)

• Other tools. They might just be expecting C# only and not know how to deal with F# projects or compiled code. Also, F#'s libraries don't ship as part of .NET, so you have a bit extra to ship around.

• But the number one issue? People. If none of your developers want to learn F#, or worse, have severe difficulty comprehending certain aspects, then you're probably toast. (Although, I'd argue you're toast anyways in that case.) Oh, and if management says no, that might be an issue.

I wrote about this a while ago: Why NOT F#?