Mixin programming foreach

[eXodiquas]

On Monday, 27 September 2021 at 16:49:15 UTC, Dga123 wrote:
> On Monday, 27 September 2021 at 16:23:50 UTC, eXodiquas wrote:
>> Howdy ho everyone,
>>
>> I found this forum very helpful for my (maybe) stupid 
>> questions, so I give it a try again because I don't understand 
>> what's happening here.
>> [...]
>> But nevertheless, I copied the code and changed it a bit to 
>> something like this:
>>
>> ```d
>> template Vector(int dimension) {
>>   string cps = "";
>>   foreach(d; 0..dimension) {
>>     cps ~= "x" ~ d ~ " = 0;\n";
>
> make a `string cps(){}` function. TemplateDeclaration can only 
> contains DeclDefs,
> i.e declarations and no expressions.
>
> b.t.w `template Vector` can also be a string `Vector(int 
> dimension){}` function.
>
> So finally to obtain something like this
>
> ```d
> import std;
>
> string vector(int dimension) {
>   string cps;
>   foreach(d; 0..dimension) {
>     cps ~= "int x" ~ d.to!string ~ " = 0;\n";
>   }
>   return "struct Vector" ~ dimension.to!string ~" {\n"  ~ cps ~ 
> "}";
> }
>
>
> mixin(vector(5));
> ```
>
> function used in mixin are evaluated at compile time and are 
> generally more perfomantly evaluated than eponymous template 
> (that contains a single member
> named as the template). Also less constraint on what can be 
> done.
>
> Have a great day,
> Dga.

I see, thank you very much for the quick answer.
So the "macro magic" does not happen in `template`, it happens in 
the `mixin` call, now I understand.

But my last question still stands, how do I build functions that 
can work with those vectors because the type of those vectors is 
created at compile time.

But I can start working on the problem now. Thanks again for 
helping me out here. :)

Have a great day aswell,

eXodiquas