digitalmars.D.bugs - [Issue 11097] New: Add version of std.algorithm.group that returns group ranges
- d-bugmail puremagic.com (41/41) Sep 22 2013 http://d.puremagic.com/issues/show_bug.cgi?id=11097
- d-bugmail puremagic.com (12/12) Sep 22 2013 http://d.puremagic.com/issues/show_bug.cgi?id=11097
- d-bugmail puremagic.com (11/11) Sep 22 2013 http://d.puremagic.com/issues/show_bug.cgi?id=11097
http://d.puremagic.com/issues/show_bug.cgi?id=11097 Summary: Add version of std.algorithm.group that returns group ranges Product: D Version: D2 Platform: All OS/Version: All Status: NEW Severity: enhancement Priority: P2 Component: Phobos AssignedTo: nobody puremagic.com ReportedBy: peter.alexander.au gmail.com 05:58:50 PDT --- std.algorithm.group returns a range of (elem, count) tuples: int[] arr = [ 1, 2, 2, 2, 2, 3, 4, 4, 4, 5 ]; assert(equal(group(arr), [ tuple(1, 1u), tuple(2, 4u), tuple(3, 1u), tuple(4, 3u), tuple(5, 1u) ][])); This is fine when the predicate is equality, but when the predicate is something else, the tuple is less useful. Here's an example of grouping strings by first character: string[] arr = [ "Alice", "Andrew", "Ben", "Bob" ]; assert(equal(group!("a.front == b.front")(arr), [ tuple("Alice", 2), tuple("Ben", 2) ])); This isn't very useful because there aren't two Alice's and two Ben's. Alice and Ben are just one element from the group (btw, the documentation doesn't indicate that it is always the first element in the group that is returned). It would be nice if there was a version of the algorithm that returned the groups themselves, working like this: string[] arr = [ "Alice", "Andrew", "Ben", "Bob" ]; assert(equal(groups!("a.front == b.front")(arr), [ ["Alice", "Andrew"], ["Ben", "Bob"] ])); I have used the identifier "groups" here. I'm not bothered what it is called. Once implemented, group may be elegantly implemented in terms of groups: auto group(alias f, R)(R r) { return groups!(f)(r).map!(g => tuple(g.front, g.walkLength)); } -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Sep 22 2013
http://d.puremagic.com/issues/show_bug.cgi?id=11097 bearophile_hugs eml.cc changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |bearophile_hugs eml.cc This good idea (that makes group more similar to the Python groupby) was discussed several times in past (even by Andrei), so I suggest you to search if this is already in Bugzilla. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Sep 22 2013
http://d.puremagic.com/issues/show_bug.cgi?id=11097 Peter Alexander <peter.alexander.au gmail.com> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|NEW |RESOLVED Resolution| |DUPLICATE 07:17:04 PDT --- *** This issue has been marked as a duplicate of issue 5968 *** -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Sep 22 2013