[Octave-bug-tracker] [bug #58953] Error with 'end' in index expression with nested function calls

[Fernando]

Follow-up Comment #38, bug #58953 (project octave):

It seems that you are almost there. However, there is some confusion between
builtin and custom methods for subsref and END.

I defined yet another class, which redefines both subsref and END methods:


classdef myclass2 < handle
  properties
    data
  end
  methods
    function obj = myclass2(data)
      obj.data = data;
    end
    function r = subsref(obj,S)
      fprintf('-----------------\n')
      S.type
      S.subs
      fprintf('-----------------\n')
      % You can use () directly on obj to access data property
      if strcmp(S(1).type,'()')
        S = [struct('type','.','subs','data'), S(1:end)];
      end
      r = builtin('subsref',obj,S);
    end
    function r = end(obj,k,n)
      fprintf('''end'' called with index=%d of %d\n',k,n);
      r = builtin('end',obj.data,k,n)-1;
    end
  end
end


In Matlab, I got:


>> obj=myclass2(1:5)
obj = 
  myclass2 with properties:
    data: [1 2 3 4 5]
>> a=obj.data(end)
-----------------
ans =
    '.'
ans =
    'data'
-----------------
-----------------
ans =
    '.'
ans =
    '()'
ans =
    'data'
ans =
  1×1 cell array
    {[5]}
-----------------
a =
     5
>> b=obj(end)
'end' called with index=1 of 1
-----------------
ans =
    '()'
ans =
  1×1 cell array
    {[4]}
-----------------
b =
     4


but in Octave I got:


octave:1> obj=myclass2(1:5)
obj =
  myclass2 object with properties:
      data: [1x5 double]
octave:2> a=obj.data(end)
'end' called with index=1 of 1
-----------------
ans = .
ans = ()
ans = data
ans =
{
  [1,1] = 4
}
-----------------
a = 4
octave:3> b=obj(end)
'end' called with index=1 of 1
-----------------
ans = ()
ans =
{
  [1,1] = 0
}
-----------------
error: index (0): subscripts must be either integers 1 to (2^63)-1 or
logicals
error: called from
    subsref at line 17 column 9


When evaluating the instruction a=obj.data(end), the END method should be
evaluated for obj.data, which is an array and not an object, so the builtin
END should be used.

When evaluating b=obj(end), the redefined END method calls the builtin END
method for obj.data, but it seems that Octave's builtin END just ignores the
arguments of that call.

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