.NET Runtime VS csharplang

.NET has explicit tailcalls - they are heavily used by and were made for F#.

https://learn.microsoft.com/en-us/dotnet/api/system.reflecti...

https://github.com/dotnet/runtime/blob/main/docs/design/feat...

The description indicates it is not production ready, and is archived at the same time.

If you pull all stops in each respective language, C# will always end up winning at parsing text as it offers C structs, pointers, zero-cost interop, Rust-style struct generics, cross-platform SIMD API and simply has better compiler. You can win back some performance in Go by writing hot parts in Go's ASM dialect at much greater effort for a specific platform.

For example, Go has to resort to this https://github.com/golang/go/blob/4ed358b57efdad9ed710be7f4f... in order to efficiently scan memory, while in C# you write the following once and it compiles to all supported ISAs with their respective SIMD instructions for a given vector width: https://github.com/dotnet/runtime/blob/56e67a7aacb8a644cc6b8... (there is a lot of code because C# covers much wider range of scenarios and does not accept sacrificing performance in odd lengths and edge cases, which Go does).

Another example is computing CRC32: you have to write ASM for Go https://github.com/golang/go/blob/4ed358b57efdad9ed710be7f4f..., in C# you simply write standard vectorized routine once https://github.com/dotnet/runtime/blob/56e67a7aacb8a644cc6b8... (its codegen is competitive with hand-intrinsified C++ code).

There is a lot more of this. Performance and low-level primitives to achieve it have been an area of focus of .NET for a long time, so it is disheartening to see one tenth of effort in Go to receive so much spotlight.

It's an interesting "time is a circle" problem given that a century only has 100 years and then we loop around again. 2-digit years is convenient for people in many situations but they are very lossy, and horrible for machines.

It reminds me of this breaking change to .Net from last year.[1][2] Maybe AA just needs to update .Net which would pad them out until the 2050's when someone born in the 1950s would be having...exactly the same problem in the article. (It is configurable now so you could just keep pushing it each decade, until it wraps again).

Or they could use 4-digit years.

[1] https://github.com/dotnet/runtime/issues/75148

These can also be passed as arguments to `dotnet publish` if necessary.

Reference:

- https://learn.microsoft.com/en-us/dotnet/core/deploying/nati...

- https://github.com/dotnet/runtime/blob/main/src/coreclr/nati...

- https://github.com/dotnet/runtime/blob/5b4e770daa190ce69f402... (full list of recognized keys for IlcInstructionSet)

Yes, that is true. I'm not sure about JVM implementation details but the reason the comment says "virtual and interface" calls is to outline the difference. Virtual calls in .NET are sufficiently close[0] to virtual calls in C++. Interface calls, however, are coded differently[1].

Also you are correct - virtual calls are not terribly expensive, but they encroach on ever limited* CPU resources like indirect jump and load predictors and, as noted in parent comments, block inlining, which is highly undesirable for small and frequently called methods, particularly when they are in a loop.

* through great effort of our industry to take back whatever performance wins each generation brings with even more abstractions that fail to improve our productivity

[0] https://github.com/dotnet/coreclr/blob/4895a06c/src/vm/amd64...

[1] https://github.com/dotnet/runtime/blob/main/docs/design/core... (mind you, the text was initially written 18 ago, wow)

If you care about portable SIMD and performance, you may want to save yourself trouble and skip to C# instead, it also has an extensive guide to using it: https://github.com/dotnet/runtime/blob/69110bfdcf5590db1d32c...

CoreLib and many new libraries are using it heavily to match performance of manually intensified C++ code.

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https://github.com/dotnet/runtime/issues/59591

Support zstd Content-Encoding:

We might not be that far away already. There is this issue[1] on Github, where Microsoft and the community discuss some significant changes.

There is still a lot of questions unanswered, but initial tests look promising.

Ref: https://github.com/dotnet/runtime/issues/94620

Not exactly related to conversation but given that you mentioned (discriminated) unions, here are notes on recent design work:

https://github.com/dotnet/csharplang/blob/main/meetings/2024...

https://github.com/dotnet/csharplang/blob/main/meetings/2024...

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.