Preprocessor for loop

[mosel00]

It would be practical to have a code generating for loop. E.g.

#for INDEX = 0 to 3
    public float x`INDEX`;  
#endfor 

would generate

public float x0;
public float x1;
public float x2;
public float x3;

and

#for INDEX = 0 to 3
    x`INDEX` = a.x`INDEX` + b.x`INDEX`;
#endfor 

would generate

x0 = a.x0 + b.x0;
x1 = a.x1 + b.x1;
x2 = a.x2 + b.x2;
x3 = a.x3 + b.x3;

I don't know what syntax it should have, but it would be nice to have it for e.g. vectors or matrices, where you have a bunch of similar operations, that should be as fast as possible, but multiple types, that only differ in the amount of fields.

[CyrusNajmabadi]

How about doing this with source-generators?

[mosel00]

It could be resolved with arrays and a normal for loop, but the code would be slower. As a reference: the second example formatted into a normal for loop with an array is about 40% slower.

[spydacarnage]

I guess it depends on your scenario. Would a stackalloc'd array work better?

[mosel00]

it can def be used with intellisense.

How? Because I could only find source-generation via strings.

Also, we shouldn't be making new language features jsut because tooling hasn't caught up with existing alpha language features. :)

Is there anything planned to generate source code, that doesn't require a new project?
Also: here it is said, that code generators can't replace code. So I can't add something like a macro or tag for the generator to look for and replace.

[mosel00]

I guess it depends on your scenario. Would a stackalloc'd array work better?

With stackalloc'd arrays, it is only 11%-17% slower. I think that's coming from the for loop itself. If that's the case, it couldn't get any faster.

[ufcpp]

What is really needed is T4 templates implemented as additional files of the source generator and well integrated in dotnet CLI and Visual Studio?

[theunrepentantgeek]

This kind of optimization is something I'd expect the compiler and/or JIT runtime to do automatically where appropriate.

I don't think the language needs to be made significantly more complex just to handle an infrastructure scenario that could be handled automatically.

Having the runtime take care of it would also provide much wider benefit.