digitalmars.D.learn - Transform a sorted range to a range of ranges of equal elements
- Tobias Pankrath (12/12) Dec 01 2014 Basically I need std.algorithm.uniq or std.algorithm.group, but
- H. S. Teoh via Digitalmars-d-learn (9/25) Dec 01 2014 Phobos git HEAD has a new range adaptor called groupBy that does what
- Tobias Pankrath (5/12) Dec 01 2014 Thanks! I wonder if this works with all input ranges. As I see
- H. S. Teoh via Digitalmars-d-learn (9/25) Dec 01 2014 The current implementation actually does work with input ranges (i.e.,
Basically I need std.algorithm.uniq or std.algorithm.group, but instead of a single element or an element and a number I want ranges that each contain consecutive elements considered equal. Example: [1,1, 2,2,2,3,4,4] -> [1, 1], [2,2,2], [3], [4,4]. Let's call this uniqRange. This way std.algorithm.uniq could be implemented as auto uniq(R, pred)(R input) { return uniqRange!pred(R).map!(r => r.front)); } Is there any elegant way to do this with using phobos? Or do I need to write my own range?
Dec 01 2014
On Mon, Dec 01, 2014 at 06:37:13PM +0000, Tobias Pankrath via Digitalmars-d-learn wrote:Basically I need std.algorithm.uniq or std.algorithm.group, but instead of a single element or an element and a number I want ranges that each contain consecutive elements considered equal. Example: [1,1, 2,2,2,3,4,4] -> [1, 1], [2,2,2], [3], [4,4]. Let's call this uniqRange. This way std.algorithm.uniq could be implemented as auto uniq(R, pred)(R input) { return uniqRange!pred(R).map!(r => r.front)); } Is there any elegant way to do this with using phobos? Or do I need to write my own range?Phobos git HEAD has a new range adaptor called groupBy that does what you want: assert([1,1,2,2,2,3,4,4].groupBy!((a)=>a).equal( [[1,1], [2,2,2], [3], [4,4]] )) T -- You have to expect the unexpected. -- RL
Dec 01 2014
Phobos git HEAD has a new range adaptor called groupBy that does what you want: assert([1,1,2,2,2,3,4,4].groupBy!((a)=>a).equal( [[1,1], [2,2,2], [3], [4,4]] )) TThanks! I wonder if this works with all input ranges. As I see it, every implementation will have to iterate the original range twice (if fully consumed). One iteration by the subranges and one to move subrange range forward. It only skimmed the code, but I'd thought that would at least require forward ranges or a buffer.
Dec 01 2014
On Tue, Dec 02, 2014 at 01:03:12AM +0000, Tobias Pankrath via Digitalmars-d-learn wrote:The current implementation actually does work with input ranges (i.e., non-forward), but with the caveat that advancing the parent range will also consume the subrange, so you have to process the subrange before advancing the parent range. It is thus single-pass for non-forward input ranges, as required (otherwise a forward range would be necessary). T -- Not all rumours are as misleading as this one.Phobos git HEAD has a new range adaptor called groupBy that does what you want: assert([1,1,2,2,2,3,4,4].groupBy!((a)=>a).equal( [[1,1], [2,2,2], [3], [4,4]] )) TThanks! I wonder if this works with all input ranges. As I see it, every implementation will have to iterate the original range twice (if fully consumed). One iteration by the subranges and one to move subrange range forward. It only skimmed the code, but I'd thought that would at least require forward ranges or a buffer.
Dec 01 2014