How to insert code in place with templates/mixins?

[rumbu]

On Monday, 20 December 2021 at 10:49:20 UTC, rempas wrote:
> On Monday, 20 December 2021 at 09:30:30 UTC, rumbu wrote:
>
> Thanks a lot for the info. When I try to use this code, I'm 
> getting the following error:
>
> ```
> Error: expression expected, not `%`
> Error: expression expected, not `%`
> ```

My fault, I forgot to put some char delimiters. You can find 
tested code here:

https://run.dlang.io/is/KfdED0

> So I suppose there is a problem with string concatenation. I 
> couldn't use it anyway because it is inefficient and because 
> I'm using betterC. Do you know any other way that I can 
> concatenate strings that does not depend an the Garbage 
> Collector or the standard library?

Enums (that's why the string is declarated as enum) are evaluated 
at compile time, the concatenation op will not end in your code 
as instruction, so you can do anything outside betterC rules as 
long you do it at compile time. You are just building some code 
to use later, the compiler does not generate any instruction for 
it.

In the example above you can press the AST button to see exactly 
how your code is generated.

Wnen you have doubts about a generated string you can always test 
it with ```pragma msg```. In this case, if you write:

```
pragma(msg, add_char!'%');
```

you will have in the output exactly what the compiler will 
generate for your mixin.