Compile-time Interfaces

[Jacob Carlborg]

On 2011-11-27 02:13, Timon Gehr wrote:
> On 11/27/2011 02:03 AM, Andrei Alexandrescu wrote:
>> On 11/26/11 6:40 PM, Kapps wrote:
>>> One of the great things about D is the ability to do so much work at
>>> compile-time, including static verification. An example is the amount of
>>> constraints available for templates, static ifs, etc. But at some point,
>>> it starts getting very problematic to just figure out what something
>>> does, and what something can do. An example for this, is ranges. They
>>> can be very confusing, and you don't know what they can do without
>>> actually going and looking up the exact definition of them. Even then,
>>> you have to know that the templated type a function expects is a range.
>>> Again, very confusing, and arguably messy. Finally, even now that you
>>> know what methods you can call on this mysterious type T, and you see
>>> that there's a clause isInputRange!(T) on the method, your IDE still has
>>> no clue about any of these things making it impossible to have
>>> semi-decent code completion for that type.
>>>
>>> Which brings in, compile-time interfaces. It seems like a natural thing
>>> to include when you have the above tools. Instead of having a method
>>> such as:
>>> auto DoSomething(T)(T Data) if(isInputRange!(T)) { }
>>> You could simply do:
>>> auto DoSomething(Range Data) { }
>>> where Range is defined as:
>>> enum interface Range {
>>> void popFront() const;
>>> @property bool empty() const;
>>> @property auto front();
>>> }
>>
>> What's "auto" here? This thing alone pretty much destroys the idea;
>> we've considered it very seriously.
>>
>> Andrei
>>
>
> I would solve that similar to this:
>
> enum interface Range {
> private alias T; // could also use 'static' instead of 'private' :o)
> void popFront();
> @property bool empty() const;
> @property T front();
> }
>
> Where "T" does not actually contribute to the imposed interface.

Then what would "T" be? Seems to me it needs to look something like this:

enum interface Range (T)
{
   void popFront();
   @property bool empty() const;
   @property T front();
}

-- 
/Jacob Carlborg