On 10/2/15 6:57 PM, Walter Bright wrote:
On 10/2/2015 10:49 AM, Eric Niebler wrote:
On Thursday, 1 October 2015 at 21:03:16 UTC, Walter Bright wrote:
I don't see evidence that C++ had ranges before D. Boost ranges are
not what
we think of as ranges.
Why not?
Because it returns iterators. It should expose functions (or operators)
that do this:
front
popFront
empty
not iterators. Instead, it has:
begin
end
empty
The begin and end are iterators, and don't encapsulate (i.e. constrain)
what can be done with those iterators. For example, begin can return an
iterator that can be used to increment right on past the end. The
iterator itself has no knowledge of where the end is.
The solution to this is cursors. i.e. ranges that point at exactly one
element.
All dcollection ranges have begin and end accessors for cursors to the
first and one beyond the last element, but unlike iterators you cannot
do anything dangerous with them.
What you CAN do, is construct ranges from them safely (there is a slight
cost for this). The interface is much superior IMO to how containers do
ranges in std.container.
There is a deficiency in ranges in that they are very fragile when it
comes to pointing at one element. Iterators are much better in this regard.
-Steve
