bugGNU Octave - Bugs: bug #56629, 'inverse' is referenced in a few...


bug #56629: 'inverse' is referenced in a few places, but is an undocumented alias for 'inv'

Submitted by:  Mike Miller <mtmiller>
Submitted on:  Sun 14 Jul 2019 07:40:58 PM UTC  
Category:  Documentation Severity:  2 - Minor
Priority:  5 - Normal Item Group:  Documentation
Status:  Fixed Assigned to:  None
Originator Name:  Open/Closed:  Closed
Release:  5.1.0 Operating System:  Any

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Tue 16 Jul 2019 05:24:06 PM UTC, comment #4: 

Looks good to me, thanks

Mike Miller <mtmiller>
Project Administrator
Mon 15 Jul 2019 09:00:59 PM UTC, comment #3: 

Easy enough.  I changed all instances of "inverse (" to "inv (" in m-files and documentation.  I added an example calling form "inverse" to the documentation for inv() and also a note explaining that "inverse" is an alias for "inv".  This also has the effect of adding an entry for "inverse" in the function index.  See https://hg.savannah.gnu.org/hgweb/octave/rev/7f5008aec7a1.

Marking as Ready for Test.

Rik <rik5>
Project Administrator
Mon 15 Jul 2019 06:36:49 PM UTC, comment #2: 

Personally I find the use of a widely accepted identifier for a well-known mathematical concept like "inverse" for some IMO relatively obscure function in some toolbox not so very appropriate. I think it's a poor, unpractical and perhaps careless choice, to say the least. But of course, this is Matlab.

FWIW, in Matlab r2019b prerelease (w/o toolboxes), "doc inverse" brings up an overview of the docs for inv, asinh, ifft, atanh, and many more "inverse" functions (87 in total), but no mention of "inverse" as a function name.

I wouldn't mind (also in my role as OF mapping package maintainer) to use "inverse" in the docs where appropriate to refer to the linear algebra operation and inverse functions in core Octave's documentation, but avoid using it as a function name proper, similar to what Matlab does. So, apart from:

>> which inverse
'inverse' is a built-in function from the file libinterp/corefcn/inv.cc

... I think Octave is already OK.

Probably it'll be quite some time before "inverse" gets implemented in the mapping package anyway.

Philip Nienhuis <philipnienhuis>
Project Member
Mon 15 Jul 2019 04:40:08 PM UTC, comment #1: 

Maybe to not get in conflict with future attempts to be compatible to some Matlab function "inverse" from some "map.geodesy.authaliclatitudeconverter" class of the Mapping toolbox


Octave should avoid this alias and not further document or populate it.

Currently the OF mapping package does not implement this function or class https://octave.sourceforge.io/mapping/overview.html

Kai Torben Ohlhus <siko1056>
Project Member
Sun 14 Jul 2019 07:40:58 PM UTC, original submission:  

The 'inv' function is well-known and documented. The 'inverse' name is a simple alias for 'inv', but it is completely undocumented in the user manual. 'help inverse' shows the docstring for 'inv', but 'doc inverse' falls back to the concept index and lands on 'pinv'.

Do we want 'doc inverse' to work, or for 'inverse' to appear in the function index? Or do we want it to be omitted from the manual intentionally?

Aside from that question, at a minimum I think we should change 'inverse' to 'inv' in the two files expr.txi and invhilb.m.

This bug report was inspired by a question in #octave by Labu.

Mike Miller <mtmiller>
Project Administrator


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    Follow 5 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2019-07-16 mtmiller StatusReady For Test => Fixed
        Open/ClosedOpen => Closed
    2019-07-15 rik5 StatusNeed Info => Ready For Test
    2019-07-15 siko1056 StatusNone => Need Info
    2019-07-14 mtmiller Carbon-CopyRemoved 80942 => -

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