On 07/13/2010 07:39 AM, Steven Schveighoffer wrote:
On Mon, 12 Jul 2010 23:48:05 -0400, Andrei Alexandrescu
<seewebsiteforem...@erdani.org> wrote:
I think I figured out a comfortable and all-encompassing means to
define a simplified interface for an input range.
Currently input ranges need to define empty, front, and popFront. That
works but it's a bit heavy for simple input ranges. We've been
discussing simplified interfaces in this group but couldn't find one
that satisfied all use cases.
Consider this:
T* getNext(R, T)(ref R range, ref T item);
Semantics: if the range wants to expose addresses of its elements, it
returns a pointer to the current element and also advances to the next
element. Otherwise (i.e. the range does not have or does not want to
expose addresses of its elements), the range fills "item" with the
current value, again moves on to the next value, and returns &item.
In all cases, when there are no more elements in the range, getNext
returns null.
getNext is easy to define for e.g. arrays and files. How does it
sound? Does it bring significant simplification?
Yes, yes, yes!
A question though -- whenever a pointer occurs, we always cringe,
especially in safeD. will getNext be unsafe?
I need to discuss this with Walter, he mentioned that it wouldn't be
difficult to allow certain uses of pointers in SafeD.
BTW, I like the alloca thingy, that's really cool.
One thing I just thought of, getNext should be split into two functions,
the one you have, and:
ElementType!R *getNext(R)(ref R range)
To avoid having to supply the item or use alloca when the range is going
to give you back a pointer to its internals anyways (tested with a
template constraint).
Yup, good point.
Andrei
