equivariant functions

[Steven Schveighoffer]

"Andrei Alexandrescu" wrote
> I discussed with Walter a variant that implements equivariant functions 
> without actually adding an explicit feature to the language. Consider:
>
> typeof(s) stripl(const(char)[] s);

As another point on this, I think someone else mentioned it, but I can't 
find the post.

I don't like the way this looks.  The way it reads is 'stripl returns the 
same type as s', but really, the typeof(s) is actually modifying the type of 
the argument also.  This seems very unintuitive.

I understand the need to not change the language, but I think most would 
prefer a syntax where the type modifier is specified on at least the 
argument.  People are going to be extremely confused when they can't treat 
's' like a normal const(char)[].

If the ultimate result is that no intuitive syntax can be made without 
changing the language, then I think it is more important to have this 
feature than to not change the language.

One other syntax that Janice proposed (and I later put into a bugzilla), is 
to use the dead keyword inout.  Meaning, what you send in is what you get 
out.  ref already completely replaces inout, so there is no need to keep it 
under its current meaning:

inout(char)[] stripl(inout(char)[] s);

I'm not in love with this completely, but it has the benefit of not 
requiring a new keyword.

-Steve