Changes in STRNCMP
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When did STRNCMP change its behaviour?
Matlab 2009a:
strncmp('asd', 'qwe', 0) % >> 0
Matlab 2011b:
strncmp('asd', 'qwe', 0) % >> 1
And in general: What is an efficient way to determine the release, when a function was changed?
[EDITED] 30-Sep-2011, 06:48 UTC
Matlab 2009a:
strncmp('a', 'a', 2) % >> 0
Matlab 2011b:
strncmp('a', 'a', 2) % >> 1
There are good arguments for the one and the other reply. But there are no good arguments for changing the behaviour of such elementary functions. It affects about 40.000 lines of my code, which directly and indirectly depends on the replied values.
I'm trying to migrate from 2009a to 2011b and this first problem stopped the tests after 3 minutes only. And there is no really convenient way to find a description when and why STRNCMP has changed. Even the bug-report is misleading:
STRNCMP and STRNCMPI return FALSE when comparing cell arrays and
considering 0 characters (i.e., with the third input set to zero).
No, it does not concern only cell arrays, but CHAR vectors also.
3 Comments
Accepted Answer
Wayne King
on 29 Sep 2011
Hi Jan, This was a bug fixed in R2010b
Hope that helps, Wayne
6 Comments
Yair Altman
on 29 Oct 2011
@Andreas - most of the respectable software vendors that I know are not ashamed in listing bug fixes when they release new versions, even if the bugs were discovered internally as in this case.
Jan's example is simply one case of many. When I upgrade my clients' software to a new release I depend on the release notes to give me an accurate description of all the changes, so that I could make an informed decision about what to check and possibly fix for the new release. If MathWorks chooses to hide this information from users then I cannot make informed decisions!
I am sorry to say that I am very disappointed with MathWorks for this.
MathWorks reportedly places huge efforts in backward compatibility, and changing things like this, *AND THEN NOT EVEN REPORTING THEM!*, makes a mockery of such efforts.
Andreas Goser
on 15 Nov 2011
I respect and understand your viewpoint and will forward it to the right person. For now, the FAQ for Bug Reports http://www.mathworks.com/support/faq/bugreportsfaq.html mentions: "6.Why aren't all bugs shown? Why isn't the bug I reported showing up? Bugs reported in this system are those that may be of interest to customers, based on general use of our products. Bugs are updated by the development team as more information and releases become available. This includes provisions for any known workarounds or file replacements. Bug report information is available for bugs either exist in or have been fixed in Release 14 SP2 or later. Information is not available for all bugs, known or unknown, including bugs in prior releases. If you feel your bug should appear in this table, contact technical support and ask that your bug be nominated as a bug report."
More Answers (2)
Kelly Kearney
on 7 Oct 2011
On the topic of history, I've requested this as an enhancement multiple times. When I wrote to the Mathworks to ask whether I could get a complete change history of a particular function (in my case, minor updates to datetick that hadn't made the release notes were affecting my code), I was told that the best way to check this was to look at the Revision line in the m-file itself.
Of course, this is only possible if you actually own all releases. I don't, but the Mathworks of does. Assuming they don't already have a centralized database of change histories for all functions, it seems to me it would be a relatively simple endeavor to write a simple file parser that reads out the revision line from each function in each release. Then users could get a clear idea of when each function was introduced, when others were phased out, and when both major and minor changes were made.
Walter Roberson
on 29 Sep 2011
I don't know when the functionality changed, but I observe that the documentation of strncmp and strncmpi were split as of 2011a. The merged 2010b page vs split 2011a page
The only "efficient" way I have found to identify changes is to request searching an older release, and then edit the URL to move between different versions. :(
2 Comments
Walter Roberson
on 29 Sep 2011
Darn. Beta version doesn't give any change history either, and also doesn't have that link near the top to the launchpad for searching specific releases.
Walter Roberson
on 29 Sep 2011
http://www.mathworks.com/help/matlab/ref/strncmp.html
is the beta page.
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