String Interpolation Compare - DIP1027 and YAIDIP

[Walter Bright]

On 10/20/2023 9:54 PM, Steven Schveighoffer wrote:
> I'm not sure I understand this. What is `dec()`?

 From https://github.com/John-Colvin/YAIDIP :

"Consider for example using stream manipulators such as dec and hex for writeln 
by using an i-string:+"

```
void fun(int x) {
     writeln(i"$dec$x in hexadecimal is 0x$hex$x.");
     // Lowering: --->
     // writeln(.object.imported!"core.interpolation".InterpolationHeader!("", 
"dec", "", "x", " in hexadecimal is 0x", "hex", "", "x", ".")(),
     //     "", dec, "", x, " in hexadecimal is 0x", hex, "", x, ".");
}
```

And:

"There is no need for defining, implementing, and memorizing a sui generis 
mini-language of encoded format specifiers"

I wasn't making false statements about that, either.


>> https://www.digitalmars.com/d/archives/digitalmars/D/Just_another_example_of_missing_string_interpolation_370542.html#N370696
> 
> mysql requires a string as the sql for the prepared statement. Basically, you 
> pass a string with a different type of placeholder specifier "?". It does not 
> accept "%s". This is not something I have any control over.

See my example. There's no reason it cannot be extended to replace the %s with 
whatever is needed. Also, DIP1027 provides the { } syntax enabling insertion of 
whatever placeholder specifier is needed.


> So naturally, since you only get a runtime format string from DIP1027, you need 
> to create an equivalent runtime string to pass to the library. How can you do 
> that without allocations?

The { } syntax. But even if you needed an allocation, a malloc/free pair will 
suffice. The problem with dec() is dec() returns an allocated string, so the 
free gets messy.

>> But even if you did rewrite it, it doesn't escape the template function, and 
>> can be RAII'd.
> 
> That is not comparable to building the correct string at compile-time. It also 
> requires *parsing* the format string at runtime.

I'd agree that parsing it is a last resort if the { } also fails. But having 
implemented formatted writes, I can attest that parsing it is not a big deal. 
It's scanning till you see the %, then substitute your own version. Of course, 
using { } means the compiler does it for you at compile time.