The state of string interpolation

Steven Schveighoffer schveiguy at
Thu Dec 6 20:08:20 UTC 2018

On 12/6/18 2:52 PM, Adam D. Ruppe wrote:

> Passing the actual variable as a CT arg is doable.. but only if there IS 
> an actual variable.
> i"hi $(name)"; // could pass T!("hi ", name)
> i"hi $(a+b)"; // error: cannot read variables at compile time

Yeah, I know. I was hoping we could bend the rules a bit in this case. 
Since an interpolation would be a different kind of alias (with special 
traits attached), it could have its own allowances that normally don't 
happen. Make it like a lazy alias ;)

> Now, maybe we don't want to support $(a+b)... but I think people would 
> miss it. How many times in PHP or Ruby or whatever do we say:

We have to support it. Of course, it would be supported for the runtime 
mechanism (where you lose the compile-time introspection). But it would 
be cool to have the compile-time traits allowed as well.

> (BTW it is interesting passing an int to a function with an interpolated 
> string. but since it doesn't automatically convert and just does a 
> tuple.. you can totally do that.)

This is why I think the idea is different and vastly superior to most 
other language string interpolation mechanisms.


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