On 2010-12-10 21:28:43 -0500, Andrei Alexandrescu
<seewebsiteforem...@erdani.org> said:
On 12/10/10 6:25 PM, Michel Fortin wrote:
One problem I'm starting to realize is that we now have so many
available qualifiers for function parameters than it's really easy to
get lost.
In D1 it was simple: "in" for regular arguments (the default),
"inout"/"ref" for passing arguments by refrence, and "out" for output
arguments. They all had clear semantics and not too much overlap.
In D2, we've lost this simplicity. Add "const/immutable/shared", add
"scope", change "in" as an alias for "const scope", give "inout" a
totally new meaning, keep "ref" and "out" the same except that now "ref"
can be prefixed with "auto" to give it a double meaning... choosing the
right modifiers for function parameters is getting extra complicated.
Have we lost track of one of D's principles, that doing the right thing
should be the easiest way to do things? To me it looks like we're adding
more and more ways to pass arguments because the defaults are failing
us. Perhaps it's time to revisit how arguments are passed by default.
As for "auto ref", if we're to keep it I think it'd be much better if it
was a keyword of its own, such as "autoref". Having modifiers is one
thing, but having modifiers that apply to modifiers is getting a little
hard to parse in my head. This is not unprecedented, in English when one
qualifier apply to another and it becomes hard to read we group them by
adding a hyphen between the two.
It's sort of ironic. You just argued for the utility of, and
implemented, another type constructor yourself!
Yeah, I know it's a little ironic. There's a difference though.
The problem I'm trying to illustrate here is that you'll need to be an
expert to choose the right one depending on the situation. How many
times have you seen someone pass std::string by copy in C++? You need a
lot of training to get this right all the time because it's not the
simpler way to pass parameters. Will the compiler complain when you
pass a parameter by value instead of passing it by 'auto ref'?
As for the optional 'ref' suffix I added in my patch for tail-const,
it's simply the continuation of the same syntax for pointers. It's not
a type constructor. It's only a way to make explicit the
already-existing implicit reference that classes have so you can apply
type constructors separately to it. I doubt people will get it wrong
often because in most situations the compiler will complain when you
should have made the ref mutable and you haven't. There's no
inefficiency by default here.
--
Michel Fortin
michel.for...@michelf.com
http://michelf.com/
