Re: difference of cell arrays behavior between octave-3.0.5 and octave-3.4.2

[Ben Abbott]

On Aug 1, 2011, at 12:07 PM, Sergei Steshenko wrote:

> --- On Mon, 8/1/11, Ben Abbott <address@hidden> wrote:
> 
>> From: Ben Abbott <address@hidden>
>> Subject: Re: difference of cell arrays behavior between octave-3.0.5 and 
>> octave-3.4.2
>> To: "Sergei Steshenko" <address@hidden>
>> Cc: address@hidden
>> Date: Monday, August 1, 2011, 5:07 AM
>> 
>> On Aug 1, 2011, at 5:31 AM, Sergei Steshenko wrote:
>> 
>>> In octave-3.0.5 I have:
>>> 
>>> "
>>> octave:1> foo{1}(:) = []
>>> foo =
>>> 
>>> {
>>>   [1,1] = [](0x0)
>>> }
>>> 
>>> octave:2> foo{2}(:) = [2;3]
>>> foo =
>>> 
>>> {
>>>   [1,1] = [](0x0)
>>>   [1,2] =
>>> 
>>>      2   3
>>> 
>>> }
>>> 
>>> octave:3> 
>>> ".
>>> 
>>> In octave-3.4.2 I have:
>>> 
>>> "
>>> foo{1}(:) = []
>>> foo =
>>> {
>>>   [1,1] = [](0x0)
>>> }
>>> octave:2> foo{2}(:) = [2;3]
>>> error: A(I) = X: X must have the same size as I
>>> octave:2>
>>> ".
>>> 
>>> 
>>> Why is it so that in octave-3.4.2 I have an error ?
>>> 
>>> Why at all size checking kicks in - "foo{2}(:)"
>> doesn't yet have size,
>>> it should be created according to RHS.
>>> 
>>> Which of the two behaviors is nominally correct
>> (Matlab) ?
>> 
>>>> clear all
>>>> foo{1}(:) = []
>> 
>> foo = 
>> 
>>     {[]}
>> 
>>>> foo{2}(:) = [2;3]
>> ???  In an assignment  A(:) = B, the number of
>> elements in A and B
>> must be the same.
>> 
>>>> foo{2}(1:2) = [2;3]
>> 
>> foo = 
>> 
>>     []    [1x2 double]
>> 
>> I compared with the developers sources (default branch) and
>> see that his last command works there as well.
>> 
>> Ben
>> 
>> 
>> 
> 
> So, do I understand correctly - your screen session is from Matlab and
> it doesn't accept
> 
> foo{2}(:) = [2;3]
> 
> like I experienced ?

Yes. ML did not accept that syntax.

> octave:1> foo{1}(:) = []
> foo =
> {
>  [1,1] = [](0x0)
> }
> octave:2> foo{2}(:) = [2;3]
> error: A(I) = X: X must have the same size as I
> octave:2>              
> ".
> 
> So, a practical question - how do I achieve what I want ? Isn't cell array
> supposed to hold values of possibly different sizes per index ?
> 
> Thanks,
>  Sergei.

The error isn't actually related to cells. For example, ...

        a(:) = [1;2];
        error: A(I) = X: X must have the same size as I

The syntax that works is just ...

        a = [1;2];

For you cell, you can just write ...

        foo{2} = [2;3];

Ben