bugGNU Octave - Bugs: bug #48693, classdef subsref method is not...


bug #48693: classdef subsref method is not called with correct nargout value

Submitted by:  Mike Miller <mtmiller>
Submitted on:  Wed 03 Aug 2016 10:02:56 PM UTC  
Category:  Interpreter Severity:  3 - Normal
Priority:  5 - Normal Item Group:  Matlab Compatibility
Status:  None Assigned to:  None
Originator Name:  Open/Closed:  Open
Release:  dev Operating System:  Any

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Wed 03 Aug 2016 10:02:56 PM UTC, original submission:  

In a classdef handle class, the subsref method is supposed to be called with `nargout` set to the number of values that the indexing argument addresses.

This works for old-style struct-based classes, but not for classdef classes.

Given the following constructor

classdef foo < handle

and the following simple definition of subsref

function varargout = subsref (x, idx)
  varargout = num2cell (zeros (size (idx(1).subs{1})));

Then the following only returns a single value, even though the indexing operation is over a range of 10 values, and nargout should be set accordingly to capture 10 values:

>> x = foo;
>> x{1:10}
ans = 0
>> y = {x{1:10}}
y =
  [1,1] = 0

but, assigning to the right number of output values gets the correct output

[y{1:10}] = x{1:10}

If foo is changed to be a struct-based class with the following constructor, but the subsref method is left exactly the same,

function y = foo ()
  y = class (struct (), "foo");

then nargout is set correctly and the indexing examples work as expected.

This is a difference in how subsref is implemented in the octave_class vs octave_classdef classes.

Mike Miller <mtmiller>
Project Administrator


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Follows 1 latest change.

Date Changed by Updated Field Previous Value => Replaced by
2019-02-26 mtmiller Carbon-CopyRemoved 80942 => -

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