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https://issues.apache.org/jira/browse/LANG-1627?focusedWorklogId=768903&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-768903
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ASF GitHub Bot logged work on LANG-1627:
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Author: ASF GitHub Bot
Created on: 11/May/22 08:42
Start Date: 11/May/22 08:42
Worklog Time Spent: 10m
Work Description: kinow commented on PR #890:
URL: https://github.com/apache/commons-lang/pull/890#issuecomment-1123372654
> Hi, I'm happy to merge them. It was purely because they seemed to two
distinct things. One improving the existing javadoc, and one adding additional
functionality.
Thanks, that's definitely good to try to split into separate pull requests
when there are multiple tasks within an issue, but I think it should be fine to
include the documentation/Javadoc clarification in the same PR. They can be
squashed as a single commit too :+1:
Issue Time Tracking
-------------------
Worklog Id: (was: 768903)
Time Spent: 0.5h (was: 20m)
> BooleanUtils.xor not behaving as expected with any odd number of true's
> -----------------------------------------------------------------------
>
> Key: LANG-1627
> URL: https://issues.apache.org/jira/browse/LANG-1627
> Project: Commons Lang
> Issue Type: Bug
> Affects Versions: 3.11
> Reporter: Alberto Scotto
> Priority: Major
> Time Spent: 0.5h
> Remaining Estimate: 0h
>
> Hi,
> I was expecting a xor function that takes a variable number of arguments to
> *return true if and only if exactly one among all of the arguments is true*,
> regardless of the number of arguments.
> This holds true given three false's:
> {code:java}
> @Test
> public void threeFalse() {
> boolean[] bools = new boolean[]{Boolean.FALSE, Boolean.FALSE, Boolean.FALSE};
> assertFalse(BooleanUtils.xor(bools));
> }{code}
>
> It also holds true given 4 true's, as well as for any even number of trues.
> {code:java}
> @Test
> public void fourTrue() {
> boolean[] bools = new boolean[]{Boolean.TRUE, Boolean.TRUE,
> Boolean.TRUE, Boolean.TRUE};
> assertFalse(BooleanUtils.xor(bools));
> }
> {code}
> The above tests pass.
> But with any odd number of true's that doesn't hold anymore:
>
> {code:java}
> @Test
> public void threeTrue() {
> boolean[] bools = new boolean[]{Boolean.TRUE, Boolean.TRUE, Boolean.TRUE};
> assertFalse(BooleanUtils.xor(bools));
> }
> {code}
> This test fails.
> That was totally unexpected to me.
> But as it turns out, even
> {noformat}
> true ^ true ^ true{noformat}
> evaluates to true. That was unexpected too to me, at a first sight.
> The thing is that xor (I mean the original boolean operator) is a binary
> operator, so if you want to make it n-ary, one simple solution is to apply it
> in two by two: ((a ^ b) ^ c) ^ d
> And that's what is done in the implementation of the method BooleanUtils#xor.
> But that brings to BooleanUtils.xor(true, true, true) == true, and at the
> same time BooleanUtils.xor(true, true, true, true) == false, which just
> doesn't sound right to me.
> Whether or not you agree with me that that is a bug of the method, please at
> least update the Javadoc, because right now it is not providing the user
> enough information. Look:
> {code:java}
> Performs an xor on a set of booleans.
> BooleanUtils.xor(true, true) = false
> BooleanUtils.xor(false, false) = false
> BooleanUtils.xor(true, false) = true
> {code}
>
> Thanks.
> Cheers
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