On 29/01/2022 02:35, antispam@math.uni.wroc.pl wrote:
> James Harris <james.harris.1@gmail.com> wrote:
>> On 16/11/2021 16:11, David Brown wrote:
>>> On 16/11/2021 16:16, luserdroog wrote:
>>
>>>> I've been following with interest many of the threads started
>>>> by James Harris over the year and frequently the topic of
>>>> namespaces and modularity come up. Most recently in the
>>>> "Power operator and replacement..." thread.
>>>>
>>>> And I tend to find myself on James' side through unfamiliarity
>>>> with the other option. What's the big deal about namespaces
>>>> and modules? What do they cost and what do they facilitate?
>>
>> ...
>>
>>> namespace timers {
>>> void init();
>>> void enable();
>>> int get_current();
>>> void set_frequency(double);
>>> }
>>>
>>> You can use them as "timers::init();" or by pulling them into the
>>> current scope with "using timers; enable();".
>>
>> As this is about namespaces, I'd suggest some problems with that "using
>> timers" example:
>>
>> * AIUI it mixes the names from within 'timers' into the current
>> namespace. If that's right then a programmer taking such an approach
>> would have to avoid having his own versions of those names. (I.e. no
>> 'enable' or 'init' names in the local scope.)
>
> I did not check C++ rules here. But other languages have simple rule:
> local name wins. That is to access global one you either should
> not declare local one or use qualified version.
>
> If you think about this for a while you should see that this is
> the only sensible rule: imported modules can change without
> programmer of "client" module knowing this. And breakning clients
> by merely adding new export is in most cases not acceptable.

There's another option: Require all imported names to be within a local
name. For example,

import timers as t

then any names that happened to exist within timers could be referred to
such as t.init and t.enable. The name t would be local and thereby
manifestly distinguishable from other local names. There would be no
possibility of the import causing an inadvertent conflict even if a
later version of 'timers' were to have other names added to it.

--
James Harris