bugGNU Octave - Bugs: bug #53425, factor.m: Octave producing neither...

 
 

bug #53425: factor.m: Octave producing neither error nor correct result

Submitted by:  Dildar Sk <hodor123456>
Submitted on:  Thu 22 Mar 2018 06:22:55 PM UTC  
 
Category:  Octave Function Severity:  3 - Normal
Priority:  5 - Normal Item Group:  Missed Error or Warning
Status:  Fixed Assigned to:  None
Originator Name:  Dildar Sk Open/Closed:  Closed
Release:  dev Operating System:  Any

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Tue 17 Apr 2018 12:40:09 AM UTC, comment #5: 

I used the first patch, i.e., not allowing negative numbers as inputs which is just what Matlab does.  I modified it to put all of the validation conditions into a single if block because it is clearer that way.  The final changeset is here http://hg.savannah.gnu.org/hgweb/octave/rev/cac96fd5310d.

Marking as fixed and closing report.

Rik <rik5>
Project Administrator
Fri 23 Mar 2018 05:54:07 PM UTC, comment #4: 

If that is the case,
I am providing another patch following,
which will just switch to positive number if it's negative number.
So,I submitted two patches(different method) and whatever Octave community thinks good can choose.But as per MATLAB compatibility
it should throw an error which I submitted first.Another patch attached.

(file #43652)

Dildar Sk <hodor123456>
Fri 23 Mar 2018 04:20:06 PM UTC, comment #3: 

Again, Octave tries to be a superset of Matlab.  We could simply emit an error, as Matlab does.  Alternatively, for negative integers (-N) we could produce factor (N) and then reverse the sign of the first factor.  Sample code:

neg_q = false;
if (q < 0)
  neg_q = true;
  q = -q;
endif

...
normal algorithm
...

if (neg_q)
  pf(1) = -pf(1);
endif

I'm not a number theory person so I don't know which option is preferred.  You could ask on the Octave-Maintainers list and maybe that is someone's area of expertise.

Rik <rik5>
Project Administrator
Fri 23 Mar 2018 08:05:22 AM UTC, comment #2: 

According to the present documentation and stable implementation, a prime number as defined by Octave's isprime need not be positive. This should be made consistent.

Michael Leitner <mleitner>
Thu 22 Mar 2018 06:28:39 PM UTC, comment #1: 

I changed the warning,error message.
Updated the function and added a test.
Patch attached.

(file #43634)

Dildar Sk <hodor123456>
Thu 22 Mar 2018 06:22:55 PM UTC, original submission:  

When I am trying on MATLAB,

>> factor(-20)

Error using factor (line 23)
N must be a real nonnegative integer.

>> factor(-35)

Error using factor (line 23)
N must be a real nonnegative integer.

Where on Octave,

>> factor(-20)

ans = -20

>> factor(-40)

ans = -40

>>


So,neither the answers are correct nor it's giving any error,warnings.

Dildar Sk <hodor123456>

 

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Attach Files:
   
   
Comment:
   

Attached Files
file #43634:  factor.patch added by hodor123456 (1KiB - text/x-patch)

 

Depends on the following items: None found

Items that depend on this one: None found

 

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    Follow 7 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2018-04-23 rik5 StatusConfirmed => Fixed
        Open/ClosedOpen => Closed
    2018-03-23 hodor123456 Attached File- => Added factor_another_method.patch, #43652
    2018-03-22 philipnienhuis StatusNone => Confirmed
        Operating SystemGNU/Linux => Any
        SummaryOctave producing neither producing error nor correct result where MATLAB is doing => factor.m: Octave producing neither error nor correct result
    2018-03-22 hodor123456 Attached File- => Added factor.patch, #43634

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