Comptime – C# meta-programming with compile-time code generation and evaluation

Post by Const-me » Thu, Dec 25, 2025, 7:05 PM UTC

eterm wrote: post #5

mfro wrote: post #2

This seems like the kind of feature that should be built into MSBuild.

It's a lot less ergonomic but there are source generators in C# : https://devblogs.microsoft.com/dotnet/introducing-c-source-g... That said, for more complex results, you'd typically load a serialization on start. I can see the value in this tool, but there must be a fairly limited niche which is too expensive to just have as static and run on start-up and cache, but not so large you'd prefer to just serialize, store…

Post by tubs » Thu, Dec 25, 2025, 7:33 PM UTC

Const-me wrote: post #61

eterm wrote: post #5

Earlier quoted context omitted.

It's a lot less ergonomic but there are source generators in C# : https://devblogs.microsoft.com/dotnet/introducing-c-source-g... That said, for more complex results, you'd typically load a serialization on start. I can see the value in this tool, but there must be a fairly limited niche which is too expensive to just have as static and run on start-up and cache, but not so large you'd prefer to just serialize, store…

> there are source generators Last time I tried them discovered source generators in the current .NET 10 SDK are broken beyond repair, because Microsoft does not support dependencies between source generators. Want to auto-generate COM proxies or similar? Impossible because library import and export are implemented with another source generators. Want to generate something JSON serializable? Impossible because in mod…

Post by estimator7292 » Thu, Dec 25, 2025, 8:04 PM UTC

Zambyte wrote: post #11

smcnc wrote: post #8

I think Zig really shines here: https://ziglang.org/documentation/master/#comptime

A key difference is that in this C# package, `[Comptime]` is an attribute (annotation? not sure on the C# term) applied to methods. In Zig, the `comptime` keyword can be applied to pretty much any expression. In the C# package, if you want to do factorial at runtime and at compile time, (I think, from reading the README) you need to define the same function twice, one with `[Comptime]` and once without. Contrast this…

Post by zmj » Thu, Dec 25, 2025, 10:43 PM UTC

maltalex wrote: post #33

andix wrote: post #31

Earlier quoted context omitted.

Array also implements IReadOnlyList if I'm not mistaken. I think C# doesn't really have immutable collections, they just can be typecasted to IReadonly* to hide the mutable operations. But they can always be typecasted back to their mutable base implementation. The only real immutable collections I know of, are F#s linked lists.

Immutable collections exit, they were just added later. See System.Collections.Immutable: https://learn.microsoft.com/en-us/dotnet/api/system.collecti...

Post by olidb » Fri, Dec 26, 2025, 5:25 PM UTC

octopoc wrote: post #64

zigzag312 wrote: post #50

Earlier quoted context omitted.

I agree, .NET Standard limitation unnecessarily complicates development experience. I think it's because some tools (Visual Studio) is still use legacy .NET Framework. I don't understand why they didn't integrate them via out of process architecture into these tools, since source generators didn't exist in the legacy framework anyway. I sometimes generate code from plain CLI projects (avoiding source generators altog…

.NET standard isn’t the biggest issue with making source generators. You can’t add dependencies to your project, which is an absolutely huge oversight IMO.