Ranges

[Yigal Chripun]

Steve Teale wrote:
> Robert Fraser Wrote:
> 
>> Steve Teale wrote:
>>> template isInputRange(R)
>>> {
>>>     enum bool isInputRange = is(typeof(
>>>     {
>>>         R r;             // can define a range object
>>>         if (r.empty) {}  // can test for empty
>>>         r.popFront;          // can invoke next
>>>         auto h = r.front; // can get the front of the range
>>>     }()));
>>> }
>>>
>>> I can not possibly be the only D enthusiast who finds this completely incomprehensible. 
>> Yeah, that one is a bit tricky, and what makes it worse is that it seems 
>> officially sanctioned by Walter/Andrei as the "right way" to check if a 
>> type supports some operations. Basically, if you have:
>>
>> is(typeof({ @@@ }()));
>>
>> this means "if I made a function containing @@@, would that function 
>> compile?". It's a hack which stems from the way the is expression works.
>>
>>> What is a range?
>> As others have mentioned, it's just a struct (or other type) that 
>> happens to support certain operations.
> 
> So does this mean that interfaces are just a tragic mistake. I'd always thought that what you said was a pretty good description of what an interface is!
> 

IMHO, duck-typing in D is a tragic mistake...  This should have been 
implemented with compile time interfaces.