digitalmars.D.bugs - [Issue 12583] New: Allow user defined "retro" range
- d-bugmail puremagic.com (32/32) Apr 15 2014 https://issues.dlang.org/show_...
https://issues.dlang.org/show_bug.cgi?id=12583 Issue ID: 12583 Summary: Allow user defined "retro" range Product: D Version: D2 Hardware: All OS: All Status: NEW Severity: enhancement Priority: P1 Component: Phobos Assignee: nobody puremagic.com Reporter: monarchdodra gmail.com I have a use case, where I have a range [*] "Range myRange" whose behavior is biased in favor of forwards iteration. Backwards iteration is also possible, but more costly. That said, I have a RetroRange, that iterates the same thing as my Range, but in reverse order, and more efficiently than what I'd get with "retro(myRange)". I've implemented the "retro()" member functions on both these ranges, so flipping iteration scheme is as simple as calling ".retro()". I think the "retro()" member function should be a range trait that is recognized by std.range.retro. This way, one can write either of "myRange.retro()" or "retro(myRange)" and have the same, customized high performance result. -------- [*] These kinds of range are usually those that iterate over containers, where it is most efficient to store _first and _pastTheEnd elements. In particular, linked list or binary trees. Other ranges could also benefit from this approach. For example, zip: finding the back of zip is no trivial operation. However, a type specifically designed to zip backwards could be *much* more efficient. --
Apr 15 2014