• Quirin Schroll (19/19) Jun 27 Let function and template parameters carry optionally a
• Richard (Rikki) Andrew Cattermole (7/26) Jun 27 It can be really useful to forward such arguments from one function to

Quirin Schroll <qs.il.paperinik gmail.com> writes:

Let function and template parameters carry optionally a 
visibility attribute. For example:
```d
void log(
     string message,
     private int line = __LINE__,
     private string func = __FILE_FULL_PATH__
);
```

In another module, `log` can be called, but the `line` parameter 
cannot be set explicitly as it’s not visible. That way, the 
author or a library can ensure that magic default values for some 
parameters are indeed applied. The user has the advantage that it 
is harder to use such a function incorrectly, e.g. `log("current 
step: ", i)` accidentally passes something entirely unrelated to 
`line`.

Another example would be to alleviate the need for a `private` 
overload that has more parameters and is called by the `public` 
one.

"Richard (Rikki) Andrew Cattermole" <richard cattermole.co.nz> writes:

On 28/06/2024 5:26 AM, Quirin Schroll wrote:
 Let function and template parameters carry optionally a visibility 
 attribute. For example:
 ```d
 void log(
      string message,
      private int line = __LINE__,
      private string func = __FILE_FULL_PATH__
 );
 ```
 
 In another module, `log` can be called, but the `line` parameter cannot 
 be set explicitly as it’s not visible. That way, the author or a library 
 can ensure that magic default values for some parameters are indeed 
 applied. The user has the advantage that it is harder to use such a 
 function incorrectly, e.g. `log("current step: ", i)` accidentally 
 passes something entirely unrelated to `line`.
 
 Another example would be to alleviate the need for a `private` overload 
 that has more parameters and is called by the `public` one.

It can be really useful to forward such arguments from one function to 
another.

I'm not convinced that this is what we need.

We could instead introduce named parameters which can only be set via a 
named argument that would archive the prevention of accidental passing 
of values, whilst keeping it explicitly settable.