String Interpolation

[duckchess]

On Sunday, 22 October 2023 at 23:44:34 UTC, Adam D Ruppe wrote:
> On Sunday, 22 October 2023 at 22:57:30 UTC, duckchess wrote:
>> or improve the language, so we can express what we want in a 
>> library.
>
> That's what the enhanced interpolation implementation does.
>
> https://github.com/adamdruppe/interpolation-examples
>
> Look down the examples here (and I have more coming as i find 
> time to write them). How would you do them with your proposal?

```d
     /** make this work **/
     writefln(mixin(`InterpolationHeader!("", "greeting", ", ", 
"name", "", "exclamation", "")(), "", greeting, ", ", name, "", 
exclamation, ""`));

     /** so it becomes this **/
     writefln(InterpolationHeader!("", "greeting", ", ", "name", 
"", "exclamation", "")(), "", greeting, ", ", name, "", 
exclamation, "");

     /************************/

     /** then add smtn to D to automatically mix in strings at the 
call side **/
     mixin(string) t(string s)() {
         // todo: code that actually generates the return string
         return `InterpolationHeader!("", "greeting", ", ", 
"name", "", "exclamation", "")(), "", greeting, ", ", name, "", 
exclamation, ""`;
     }
     writefln(t!"$greeting, $name$exclamation");

     /** turns into **/
     writefln(mixin(`InterpolationHeader!("", "greeting", ", ", 
"name", "", "exclamation", "")(), "", greeting, ", ", name, "", 
exclamation, ""`));


     /************************/

     /** this is a sketch of how i'd like the default 
implementation for i to look **/
     mixin(string) i(string s)() {
         return q{(){
             struct RESULT {
             	string toString() const { return "....."}
                 mixin(string) printfargs(){ return ".....");
             	mixin(string) seq(){ return 
`InterpolationHeader!("", "greeting", ", ", "name", "", 
"exclamation", "")(), "", greeting, ", ", name, "", exclamation, 
""`;}
         	}
         	return RESULT();
     	}()}

     }
     writeln(i!"$greeting, $name$exclamation");
     writefln(i!"$greeting, $name$exclamation".seq);

```

again, idk if this specific idea works, but this is how i'd 
imagine usercode to look like


```d
writeln(i!"Hello, $name! I liked DIP $dipNumber a lot.");
string result = i!"$name! See that DIP $dipNumber is easy to 
convert to string.";
writefln(i!"$name has $$wealth:%0.2f".seq);
printf(i!"$name is $age years old.\n".printfargs);
writeln(tr!("I, $name, have a singular apple.", "I, $name, have 
%d apples.", count));
writeln(tr!("I, $name, have a singular apple.", "I, $name, have 
$count apples."));

```