about const ref

[Mathias Lang]

On Tuesday, 11 February 2020 at 07:51:04 UTC, Ferhat Kurtulmuş 
wrote:
> I need to be sure about "const ref". Based on the following 
> function, does it mean:
>
> Type can be string or an integral type.
>
> (a) k1 is not copied on function calls
> (b) k1 cannot be modified inside function
>
> Please correct me if I am wrong. Can storage class "in" be used 
> to satisfy (a) and (b)?
>
>
> void doIt(const ref Type k1){
>     ....
> }
>
> Type k = ...;
>
> doit(k);


You're correct for 'a' and 'b'. However `in` only entails 
`const`, so it is not an exact replacement.
Additionally, you might want to add `scope` to show that the 
parameter does not escape.

Note that a big limitation on `const ref` parameters at the 
moment is that it does not accept literals, which is something 
Andrei talked about a few years ago at DConf (or was it last 
year?).