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[CLJ-1117] Partition does not follow docs Created: 29/Nov/12  Updated: 17/May/13

Status: Open
Project: Clojure
Component/s: None
Affects Version/s: Release 1.6
Fix Version/s: None

Type: Defect Priority: Minor
Reporter: Timothy Baldridge Assignee: Unassigned
Resolution: Unresolved Votes: 0
Labels: None
Environment:

OS X, 10.8

Attachments: Text File clj-1117.patch    
Patch: Code

 Description   

The doc for partition states "In case there are not enough padding elements, return a partition with less than n items."

However, the behavior of this function is as follows:

user=> (partition 3 (range 10))
((0 1 2) (3 4 5) (6 7 8))
user=> (partition 4 (range 10))
((0 1 2 3) (4 5 6 7))
user=> (partition 5 (range 10))
((0 1 2 3 4) (5 6 7 8 9))

Either the doc should be updated to make it clear that not providing a pad will mean that items are dropped, or the functionality of partition should be fixed to the following:

user=> (partition 3 (range 10))
((0 1 2) (3 4 5) (6 7 8) (9))

 Comments   
Comment by Andy Fingerhut [ 29/Nov/12 2:15 PM ]

That would be a potentially breaking change for some people's code that uses partition. partition-all behaves as you wish.

Also, your concern with the documentation is for when there are padding elements specified as an argument, but your examples don't specify any padding elements.

Comment by Timothy Baldridge [ 29/Nov/12 2:55 PM ]

I agree, but I think the docs should then explicitly state: "if no padding is given, not all input elements may be returned in the output partitions" or something to that line.

Comment by Andy Fingerhut [ 29/Nov/12 4:43 PM ]

More precise documentation of current behavior is always welcome in my opinion.

Comment by Gabriel Horner [ 17/May/13 10:14 AM ]

I've uploaded a patch that calls out when and how partition drops tail elements:
"If a pad collection is not supplied, any tail elements that remain from dividing the input collection length by n will not be included in a partition."

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