F# VS csharplang

F# F*

This year I've been attempting Advent of Code in my favourite programming language, F#. This is a beginner(ish) centered post about making incremental changes from the smallest possible solution to something more robust.

I can recommend polyglot notebooks in vs code, so you can mix different languages.Take a look athttps://fsharp.org/ for some project ideas and frameworks.

I have many less followers on Mastodon than in the Birdsite (40 vs 341), yet my activity has generated many more interactions than there. Not only that, among the users who decided to interact with me I counted: a co-discoverer of the Laniakea supercluster, one of the lead developers behind F#, the author of many important books on Java & JVM, plus many others. I'm literally a nobody, but this time there was no algorithm relying on relevance and engament metrics to decide what to present to each one of us.

FP devs differ based on language here. Elm, like F#, tends to encourage "a bunch of functions and types in a file". While Elm supports modules, we don't really care where it came from; they're all pure, all deterministic, the compiler tells us if it works.

The builtin fsharp collections actually are just "immutable", not persistent as you mention. (Ref: https://github.com/fsharp/fsharp/blob/master/src/fsharp/FSharp.Core/map.fs. This is just an AVL tree that returns a copy on mutations: https://github.com/fsharp/fsharp/blob/577d06b9ec7192a6adafefd09ade0ed10b13897d/src/fsharp/FSharp.Core/map.fs#L118)

You can dive into .NET ecosystem by trying F#. It's functional-first language so this should be familiar.

ReScript code is just like F# or OCAML; it doesn’t have a function parse phase like JavaScript, so we have to define our functions and types first before we can use them. That’s fine, but makes explaining the code backwards (meaning you start at the bottom of the file and work your way up), so we’ll start at our lambda handler and explain each part, regardless of where it’s defined.

F# is a JavaScript and .NET language for web, cloud, data-science, apps and more.

Also a programming joke

Certain parts of Microsoft Learn are permissive, for example the .NET BCL documentation is Creative Commons Attribution: https://github.com/dotnet/dotnet-api-docs as is ASP.NET Core: https://github.com/dotnet/AspNetCore.Docs (a good hint if documentation is permissively licensed and on GitHub is if there's an edit button at the top.)

The C# language specification is unfortunately a bit fuzzier: https://github.com/dotnet/csharplang/discussions/4855

The updated unified C# language specification is CC, but it's still catching up to modern C#: https://github.com/dotnet/csharpstandard

No OP, but for example you still see the C# folks still struggling to add discriminated unions to the language because of complex interactions due to its too many features[1]. Virtual threads are easier to use than async/await is another example.

[1] https://github.com/dotnet/csharplang/issues/113

For example, C# had a research fork called Spec# that had compile-time support for contracts, with keywords such as requires (for arguments) and ensures (for return values), all the way back in 2004. While still being discussed, it doesn't seem to be shipping any time soon.

Hi there. I'm the language designer who created the 'Collection Expression' design/specification: https://github.com/dotnet/csharplang/issues/5354

You can see the entire history of the proposal there. To answer you specific question, we went with `..` because that's what the language already uses for the complimentary 'pattern matching deconstruction' form for collection patterns.

In other words, you can already say this today:

    if (x is [var start, .. var middle, .. var end]) { ... }

You must specify concrete type.

There was a plan to have "natural type" so "var list = [1,2,3]" would be of type "List" but it was postponed to C# 13 (https://github.com/dotnet/csharplang/issues/5354#issuecommen...)

While C# currently lacks direct support for this kind of functionality, there's a glimmer of hope with an active proposal under discussion that aims to bring this feature to the language. This potential addition promises a future where C# can natively offer similar robust type narrowing.

Given few people anticipated ValueTuple and C# adding a more direct tuple syntax, I feel like it is only a matter of time before C# adds discriminated unions.

(There are multiple proposals tracking the idea. This seems the most comprehensive and "central": https://github.com/dotnet/csharplang/issues/7016)

I always liked list abbreviations in python, but I absolutely love Linq. I believe there is a feature proposal for C# 12, which makes collection initialization better imo.