[Octave-bug-tracker] [bug #33221] subsasgn without LHS should do in-place assignment for performance

[Daniel Molina García]

Follow-up Comment #3, bug #33221 (project octave):

It is not only a Matlab compatibility issue, but apparently an inconsistency
with Octave documentation.


octave:1> help subsasgn
[...]
          val = magic (3);
          idx.type = "()";
          idx.subs = {":", 1:2};
          subsasgn (val, idx, 0)
               =>  [ 0   0   6
                     0   0   7
                     0   0   2 ]

     Note that this is the same as writing 'val(:, 1:2) = 0'.


However, last sentence is not correct (val is not assigned after subsasgn
call). Example that shows it:


octave:1> val = magic (3);
octave:2> idx.type = "()";
octave:3> idx.subs = {":", 1:2};
octave:4> 
octave:4> subsasgn (val, idx, 0)
ans =

   0   0   6
   0   0   7
   0   0   2

octave:5> val
val =

   8   1   6
   3   5   7
   4   9   2

octave:6> val(:, 1:2) = 0
val =

   0   0   6
   0   0   7
   0   0   2

octave:7> val
val =

   0   0   6
   0   0   7
   0   0   2



If I understand it correctly, documentation should be modified/clarified or
subsasgn implementation modified.

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