Just another example of missing string interpolation

[bachmeier]

On Thursday, 12 October 2023 at 13:39:46 UTC, Andrea Fontana 
wrote:
> Real life example. Render a string like this:
>
> ```
> \x1b[2K\r\x1b[1mProgress:\x1b[0m 50% \x1b[1m\tSpeed:\x1b[0m 
> 15.5 KB/s
> ```
>
> now (error prone and difficult to debug, try to code it!):
>
>
> ```
> stderr.write(format("%s\r%sProgress:%s %5.1f%% %s\tSpeed:%s 
> %6.1f %s%s", clear, white, clear, progress, white, clear, 
> curSpeed, unit));
> ```
>
> (or with string concat, good luck!)
>
> vs:
>
> ```
> stderr.write("${clear}\r{$white}Progress:${clear}${progress}% 
> \t${white}Speed:${clear} ${curSpeed} ${unit}");
> ```
>
> Andrea

I agree that string interpolation needs to be added to the 
language (it's 2023) but for the benefit of an outsider reading 
your message, there are better options than calling `format`. I 
use a generalization of this:

```
string interp(string s, string[string] subs) {
   foreach(k; subs.keys) {
     s = s.replace("${" ~ k ~ "}", subs[k]);
   }
   return s;
}
```

For your example, I'd call this

```
std.file.write("foo.txt",
   interp("${clear}2K\r${white}Progress:${clear}${progress}% 
\t${white}Speed:${clear} ${curSpeed} ${unit}",
   ["clear": "\x1b[", "white": "\x1b[1m",
    "progress": "0m 50", "curSpeed": "0m 15.5",
    "unit": "KB/s"]));
```

Would be much better to have this in the language, so I wouldn't 
have to specify all the substitutions, but a lot better than 
using `format` IMO.