On 6/8/2015 9:55 AM, Dennis Ritchie wrote:
On Monday, 8 June 2015 at 00:42:12 UTC, Mike Parker wrote:
When implementing a custom range, is it correct to say that
consecutive calls to r.front with no intervening calls to popFront
should return the same value?
Yes. For examle:
import std.stdio, std.range;
template foo(T) {
auto foo(R)(R range) {
while (!range.empty) {
writeln(range.front);
// .front --> the first element of the range
range.popFront;
// .popFront --> to extract the first element of the range
}
}
}
void main() {
foo!(int[])([1, 2, 3]);
}
I know how to use a range :) What I'm asking about is a requirement on
implementing front on a custom range. Is there a rule that says when I
implement my own range, consecutive calls to front must return the same
value until popFront is called?
Example:
Is this a valid implementation of front?
auto front() { return _member++; }
Or must it be this:
auto front() { return _member; }
void popFront() { ++_member; }
My current understanding is that the former is incorrect, but I'm
looking for confirmation of that. I can't find it written down anywhere.
