Re: [boost] AlRangeExandrescu?

Subject: Re: [boost] AlRangeExandrescu?
From: Andrei Alexandrescu (andrei_at_[hidden])
Date: 2009-07-25 19:09:30

Thorsten Ottosen wrote:
> Andrei Alexandrescu skrev:
>> Thorsten Ottosen wrote:
>>> Andrei Alexandrescu skrev:
>>>
>>>>>> Surprisingly, until() also works on input ranges! It works because 
>>>>>> it finds the element lazily - it returns a range that tests for 
>>>>>> termination condition in its .empty() test. So until() returns a 
>>>>>> range that iterates the original passed-in range until the sought 
>>>>>> element is found, at which time until() reports termination.
>>>>>
>>>
>>> Is until lazy for all types of ranges? Being lazy is often good, but
>>> it's so nice to compose a lazy range with other types of ranges.
> 
> A "not" slipped here.
> 
>> Yes, until is lazy. I think it couldn't be implemented any other way 
>> for input ranges.
> 
> Ok, but the problem with lazy ranges is that when you compose it with
> range adaptors, then it greatly limits the adaptors that you can 
> subsequently apply.

Why is that the case?

Andrei