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[CLJ-428] subseq, rsubseq enhancements to support priority maps? Created: 20/Aug/10  Updated: 14/Feb/14

Status: Open
Project: Clojure
Component/s: None
Affects Version/s: Backlog
Fix Version/s: None

Type: Enhancement Priority: Minor
Reporter: Assembla Importer Assignee: Unassigned
Resolution: Unresolved Votes: 2
Labels: None

Attachments: File clj-428-v4.diff    
Patch: Code and Test

 Description   

See dev thread at http://groups.google.com/group/clojure-dev/browse_thread/thread/fdb000cae4f66a95.

Note: subseq currently returns () instead of nil in some situations. If the rest of this idea dies we might still want to fix that.



 Comments   
Comment by Assembla Importer [ 24/Aug/10 10:10 AM ]

Converted from http://www.assembla.com/spaces/clojure/tickets/428

Comment by Andy Fingerhut [ 28/Apr/13 2:14 AM ]

Patch clj-428-change-Sorted-seqFrom-to-take-inclusive-patch-v1.txt dated Apr 28 2013 was written by Mark Engelberg in July 2010, and was attached to a message he sent to the dev thread linked in the description. The approach he takes is described by him in that thread, copied here:

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Meanwhile, to initiate discussion on how to modify subseq, I've attached a proposed patch. This patch works by modifying the seqFrom method of the Sorted interface to take an additional "inclusive" parameter (i.e., <= and >= are inclusive, < and > are not).

In this patch, I do not address one issue I raised before, which is whether subseq implies by its name that it should return a seq rather than a sequence (in other words nil rather than ()). If seq behavior is desired, it would be necessary to wrap a call to seq around the calls to take-while. But for now, I'm just making the behavior match the current behavior.

Although I think this is the cleanest way to address the extensibility issue with subseq, the change to seqFrom will break anyone who currently is overriding that method. I didn't see any such classes in clojure.contrib, so I don't think it's an issue, but if this is a concern, my other idea is to fix the problem entirely within subseq by changing the calls to next into calls to drop-while. I have coded this to confirm that it works, and can provide that alternative patch if desired.
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I can also supply a patch that uses drop-while in clojure.core/subseq and rsubseq if such an approach is preferred to the one in this patch.

Comment by Andy Fingerhut [ 28/Apr/13 12:12 PM ]

clj-428-change-Sorted-seqFrom-to-take-inclusive-patch-v2.txt dated Apr 28 2013 is same as clj-428-change-Sorted-seqFrom-to-take-inclusive-patch-v1.txt (soon to be deleted), except it adds tests for subseq and rsubseq, and corrects a bug in that patch. The approach is the same as described above for that patch.

Comment by Andy Fingerhut [ 01/May/13 2:44 AM ]

Patch clj-428-change-Sorted-seqFrom-to-take-inclusive-patch-v3.txt dated May 1 2013 is the same as clj-428-change-Sorted-seqFrom-to-take-inclusive-patch-v1.txt, still with the bug fix mentioned for -v2, but with some unnecessary changes removed from the patch. The comments for -v1.txt on the approach still apply.

Comment by Andy Fingerhut [ 14/Feb/14 12:20 PM ]

Patch clj-428-v4.diff is identical to clj-428-change-Sorted-seqFrom-to-take-inclusive-patch-v3.txt described in an earlier comment, except it updates some diff context lines so that it applies cleanly to the latest Clojure master as of today.

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