tdpl: partial ordering of functions: conflict error

[Jerome BENOIT]

On 18/01/12 18:05, Timon Gehr wrote:
> On 01/18/2012 05:40 PM, Jerome BENOIT wrote:
>>
>>
>> On 18/01/12 17:07, Timon Gehr wrote:
>>> On 01/18/2012 04:57 PM, Timon Gehr wrote:
>>>> On 01/18/2012 02:32 PM, Jerome BENOIT wrote:
>>>>>
>>>>>
>>>>> On 18/01/12 04:36, Jonathan M Davis wrote:
>>>>>> On Wednesday, January 18, 2012 02:33:25 Jerome BENOIT wrote:
>>>>>>> And I cannot figure why :-(
>>>>>>
>>>>>> http://d.puremagic.com/issues/show_bug.cgi?id=1528
>>>>>>
>>>>>> As a workaround, templatize the last function by changing its
>>>>>> signature to
>>>>>>
>>>>>> int[] find()(int[] longer, int[] shorter)
>>>>>
>>>>> actually it does not work either: gdmd gives an other error message
>>>>> now.
>>>>>
>>>>> ------------------------------------------------------------------------
>>>>>
>>>>> T[] find(T, E)(T[] haystack, E needle)
>>>>> if (is(typeof(haystack[0] != needle) == bool)) {
>>>>> while (haystack.length > 0 && haystack[0] != needle) {
>>>>> haystack = haystack[1 .. $];
>>>>> }
>>>>> return haystack;
>>>>> }
>>>>>
>>>>> TL[] find(TL, TS)(TL[] longer, TS[] shorter)
>>>>> if (is(typeof(longer[0 .. 1] == shorter) : bool)) {
>>>>> while (longer.length >= shorter.length) {
>>>>> if (longer[0 .. shorter.length] == shorter) break;
>>>>> longer=longer[1 .. $];
>>>>> }
>>>>> return longer;
>>>>> }
>>>>>
>>>>> int[] find()(int[] longer, int[] shorter) {
>>>>> while (longer.length >= shorter.length) {
>>>>> if (longer[0 .. shorter.length] == shorter) break;
>>>>> longer=longer[1 .. $];
>>>>> }
>>>>> return longer;
>>>>> }
>>>>>
>>>>> unittest {
>>>>> // Test the introduced overloads
>>>>> long[] a1 = [ 6, 1, 2, 3 ];
>>>>> long[] a2 = [ 1 , 2 ];
>>>>> int[] b1 = [ 6, 1, 2, 3 ];
>>>>> int[] b2 = [ 1 , 2 ];
>>>>> assert(find(a1, a2) == a1[1 .. $]);
>>>>> assert(find(a1, b2) == a1[1 .. $]);
>>>>> assert(find(b1, b2) == b1[1 .. $]);
>>>>> }
>>>>>
>>>>> void main() {}
>>>>> ------------------------------------------------------------------------
>>>>>
>>>>>
>>>>> The message is now:
>>>>> searching_05.d:34: Error: template searching_05.find(T,E) if
>>>>> (is(typeof(haystack[0] != needle) == bool)) find(T,E) if
>>>>> (is(typeof(haystack[0] != needle) == bool)) matches more than one
>>>>> template declaration, searching_05.d(9):find(TL,TS) if
>>>>> (is(typeof(longer[0..1] == shorter) : bool)) and
>>>>> searching_05.d(18):find()
>>>>>
>>>>> Is partial ordering really supported ?
>>>>>
>>>>
>>>> Yes it is, and your code snippet indeed compiles on my machine. Are you
>>>> maybe using an outdated version of the compiler?
>>>>
>>>>
>>>
>>> Nevermind, I forgot to pass the -unittest switch. It indeed gives that
>>> error. The reason it still does not compile is that the workaround
>>> proposed by Jonathan has slightly different semantics than it would
>>> have if the compiler already supported overloading of functions
>>> against function templates.
>>>
>>> If exactly one of two equally good matched functions is a templated
>>> one, the other one is chosen.
>>
>> So the D code in my first post may work and thus the workaround is not
>> necessary.
>>
>
> The language does not mandate the workaround, but the workaround is necessary until the compiler is fixed.

Thanks for the precision. So I will move to the next section and come back to this part when the compiler is fix:
I guess it will be fixed for the next release as it sounds as an important bug.

Jerome