equivariant functions

[Andrei Alexandrescu]

KennyTM~ wrote:
> Andrei Alexandrescu wrote:
>> Denis Koroskin wrote:
>>> On Mon, 13 Oct 2008 01:52:25 +0400, Andrei Alexandrescu 
>>> <SeeWebsiteForEmail at erdani.org> wrote:
>>>
>>>> Denis Koroskin wrote:
>>>>> Sorry to hit a dead horse but...
>>>>>  auto dg = &stripl; // what is the type of dg?
>>>>
>>>> stripl is three overloads. You must use a precise type on the 
>>>> receiving side to get a pointer to function, as with any overloaded 
>>>> symbol.
>>>>
>>>>> string z = dg("foo");
>>>>> char[] x = dg("foo".dup);
>>>>>  It is great that you brought the issue to discussion, but I think 
>>>>> this solution is a miss.
>>>>
>>>> I'm glad you're trying to dent it, this is the best way to find bugs 
>>>> in it. But let me note that so far you haven't gotten even near :o).
>>>>
>>>>
>>>> Andrei
>>>
>>> Ok, I'll try harder. Here is a common used pattern:
>>>
>>> interface IMaybeBar
>>> {
>>>     Bar isBar();
>>>     const(Bar) isBar();
>>>     invariant(Bar) isBar();
>>> }
>>>
>>> class Foo : IMaybeBar
>>> {
>>>     Bar isBar() { return null; }
>>>     const(Bar) isBar() const { return null; }
>>>     invariant(Bar) isBar() invariant { return null; }
>>> }
>>>
>>> class Bar : Foo
>>> {
>>>     Bar isBar() { return this; }
>>>     const(Bar) isBar() const { return this; }
>>>     invariant(Bar) isBar() invariant { return this; }
>>> }
>>>
>>> let's change it into one.
>>>
>>> interface IMaybeBar
>>> {
>>>     same(Bar) isBar() same(this); // same is shorter than sameconst 
>>> and as descriptive as sameconst
>>> }
>>>
>>> class Foo
>>> {
>>>     same(Bar) isBar() same(this) { return null; }
>>> }
>>>
>>> class Bar : Foo
>>> {
>>>     same(Bar) isBar() same(this) { return this; }
>>> }
>>>
>>> Your solution? Note that it shouldn't conflict with your clone example:
>>>
>>>> class S
>>>> {
>>>>      typeof(this) clone();
>>>> }
>>
>> Walter found an answer last night.
>>
>> interface IMaybeBar
>> {
>>     Bar isBar();
>>     const(Bar) isBar() const;
>>     invariant(Bar) isBar() invariant;
>> }
>>
>> class Foo : IMaybeBar
>> {
>>     PassQual!(typeof(this), Bar) isBar() const { return null; }
>> }
>>
>> class Bar : Foo
>> {
>>     typeof(this) isBar() const { return this; }
>> }
>>
>>
>> Andrei
> 
> What is PassQual!() ?_?

Pass the qualifiers of the first argument to the second argument. It's a 
simple template.

Andrei