On 2/1/23 16:19, Bo Persson via Std-Proposals wrote:
> On 2023-02-01 at 13:56, Andrey Semashev via Std-Proposals wrote:
>> Hi,
>>
>> Would it be possible to be able to explicitly specify default arguments
>> for template specializations and function calls?
>>
>> void foo(int x, int y = 10, int z = 20);
>>
>> foo(1, default, 3); // == foo(1, 10, 3);
>>
>>
>> // Use default ordering function
>> typedef std::set< int, default, my_alloc > my_set;
>>
>> // Use default compare and hash functions
>> typedef std::unordered_set< int, default, default, my_alloc > my_uset;
>>
>>
>> template<
>> typename T,
>> typename = whatever,
>> bool = is_special< T >::value
>> >
>> struct trait {};
>>
>> // Specialization: trait< T, whatever, true >
>> template< typename T >
>> struct trait< T, default, true > {};
>>
>> This syntax is currently invalid, so the extension would be pretty
>> harmless. This would allow to avoid code duplication, where the user of
>> the function or template, or the one who specializes the template, has
>> to duplicate the default argument when he only needs to specify the
>> arguments after that.
>
> This seems to have been proposed 20 years ago.
>
> https://wg21.link/N1466
>
> Didn't go anywhere.

Any particular reason why it got rejected or it was simply abandoned?