Wanted: Format character for source code literal

[Berni44]

On Monday, 3 May 2021 at 23:08:55 UTC, Q. Schroll wrote:
> Please don't do this. Format characters can be customized. Any 
> character you'd introduce for it either wouldn't work for some 
> types or break those types' formatting.

I think, this doesn't hurt: The call of a `toString` has 
precedence for compound types like structs and classes (and in 
most of these cases it won't be possible to add a generic literal 
at all, see my post above). So, if you use some of the predefined 
qualifiers, the customized version will always be used, even if 
it has a completely different meaning. (Admittedly it might cause 
some confusion, if the customized versions are not well 
documented.)

> Why not introduce a new function like `dlangLiteral` that takes 
> the value and returns a string? It can be used in `format` 
> quite easily (like `format("pre %s post", 
> dlangLiteral(<something>));`) and is explicit and not a special 
> case at all.

In my opinion, the main idea behind this formatting routines is, 
to have a simple and short way for formatting output. We could 
use your idea for every other format character too, like: 
`format("%s = %s", character('𝜋'), 
scientificFloatingPoint(3.14))`. We don't do that, because it's 
more convenient to write `format("%c = %e", '𝜋', 3.14)`.

Furthermore, there are all the parameters, that can be applied: 
`format("%-3c = %+.4e", '𝜋', 3.14)` is a simple way to change the 
formatting. Without it it would become something like `format("%s 
= %s", character!(true, false, false, false, false, false, 
3)('𝜋'), scientificFloatingPoint!(false, true, false, false, 
false, false, FormatSpec.UNSPECIFIED, 4)(3.14))`.

An other problem will be, when used with arrays, ranges and the 
like, e.g. you can do something like `format("val = [%(%D,\n      
  %)];", my_array);` to get an output with each value on a 
separate line. Without this literal you would at least need to 
map `my_array` using `dlangLiteral` and in generic code this 
might even cause more trouble.