Motive behind !empty() with front() instead of Optional front()

[Paul Backus]

On Tuesday, 6 April 2021 at 01:47:47 UTC, Q. Schroll wrote:
> On Friday, 26 March 2021 at 15:12:04 UTC, Paul Backus wrote:
>> Of course the ideal would be to make `ref` itself into a type 
>> qualifier (`ref(T)`).
>
> If you look at all the exceptions C++ has for its reference 
> type constructor, you'll immediately see why Walter created 
> `ref` as a storage class and not a type constructor. C++ 
> reference types in many cases don't compose; e.g. 
> `vector<int&>` isn't a thing.
> If you really think about it, you don't need `ref` as a type 
> constructor. Although allowing `ref` local variables wouldn't 
> be harmful, I guess.

Here's what the generic identity function currently looks like in 
D:

     auto ref T identity(T)(auto ref T arg)
     {
         import core.lifetime: forward;
         return forward!arg;
     }

Here's what the generic identity function *would* look like if 
`ref` were a type qualifier:

     T identity(T)(T arg)
     {
         return arg;
     }

I rest my case.