cat does not convert sparse matrices?

[Francesco Potorti`]

>> octave> a=zeros(3,3,0);
>> octave> b1=zeros(3,3);
>> octave> whos a b1
>> 
>>   Prot Name        Size                     Bytes  Class
>>   ==== ====        ====                     =====  ===== 
>>    rwd a           3x3x0                        0  double
>>    rwd b1          3x3                         72  double
>> 
>> octave> size(cat(3,a,b1))
>> ans =
>> 
>>    3   3   1
>
>Trailing singleton dimensions should be dropped

Should they really be?  This is the first step of a loop where I build a
3d matrix by catenating 2d matrices on the 3rd dim, like this:

a=zeros(3,3,0);
for z=1:Z
    b=rand(3,3);
    a=cat(3,a,b);
endfor

if cat() dropped the trailing singleton dimension, would this loop keep
working?

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