Re: Andrei's "iterators must go" presentation
Martin Eisenberg wrote:
Andrei Alexandrescu wrote:
Martin Eisenberg wrote:
Andrei Alexandrescu wrote:
The spec of find is very simple: reduce r from its front until
value is found, or r is exhausted. There's no ordering or
uniqueness requirement.
That sounds more like lower_bound. In a parallel post, George
Ryan evidently has find(r, x) := upper_bound(lower_bound(r, x),
x) in mind. That seems reasonable too when the range is in fact
sorted.
It's not quite lower_bound, as I think of lower_bound as the
"lower", left-hand side, range.
I see. That raises the question how to get from a range to its
complement, for the bounding algorithms also serve to locate the
element just inside a bound as well as the one just outside.
Returning the remainder of the range is the most general option
possible when you want to accommodate input ranges. It so
happens it turns out to be very convenient in practice.
But once you detect the lower bound in an input range, the prefix is
gone. So lower_bound is undefined on input ranges?
It is in the original, iterator-based STL and in my library. In
addition, currently my library requires a random-access range for
lower_bound. I plan to return a different type from lower_bound when an
input or forward range are passed: a lazy range of unknown length that
makes progress until it hits the sought element, at which point it
stops. That would make lower_bound more general than iterator_based STL
because it can operate on input ranges (iterator-based STL requires at
least forward ranges)>
Andrei
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