opApply Vs. Ranges: What should take precedence?

[Bill Baxter]

On Mon, Nov 23, 2009 at 4:27 AM, Steven Schveighoffer
<schveiguy at yahoo.com> wrote:
> On Fri, 20 Nov 2009 19:32:10 -0500, Bill Baxter <wbaxter at gmail.com> wrote:
>
>> On Fri, Nov 20, 2009 at 4:22 PM, Justin Johansson <no at spam.com> wrote:
>>>
>>> Bill Baxter wrote:
>>>>
>>>> On Fri, Nov 20, 2009 at 3:36 PM, Walter Bright
>>>> <newshound1 at digitalmars.com> wrote:
>>>>>
>>>>> And here I was thinking perhaps opApply should just be dumped in favor
>>>>> of
>>>>> ranges.
>>>>>
>>>>
>>>> I think the opApply should take precedence.
>>>> The only reason to define opApply is because foreach uses it.
>>>> Ranges on the other hand are useful in other situations.
>>>>
>>>> --bb
>>>
>>> Is is absolutely necessary for opApply to take a ref parameter?  (I'm
>>> asking
>>> from D1 familiarity not D2 so question might not be relevant).
>>>
>>> My understanding is that by taking a ref parameter there is an additional
>>> pointer dereference to get to the actual datum that is the subject of
>>> current application.  Of course the current regime does appear to allow a
>>> foreach to modify the items in the "container" being iterated over,
>>> though
>>> myself, I've only ever used foreach in readonly mode.
>>
>> Making the delegate's arg "const ref" seems to work in D2.
>> And prevents writing to the argument, as expected.
>
> It still requires an lvalue, which is not always convenient...
>
> I have proposed an enhancement for this, see
> http://d.puremagic.com/issues/show_bug.cgi?id=2443

Yeh, that enhancement request makes total sense.  I was certainly
baffled by the inability to use a non-ref type there, too.

--bb