[Scilab-Dev] empty sparse: sparse([]) vs sparse([],[],[0 0])

[Samuel Gougeon]

Le 22/01/2019 à 17:56, Samuel Gougeon a écrit :
> Le 22/01/2019 à 17:40, Stéphane Mottelet a écrit :
>> Le 22/01/2019 à 17:06, Samuel Gougeon a écrit :
>>> Le 22/01/2019 à 16:34, Stéphane Mottelet a écrit :
>>>> Le 22/01/2019 à 16:25, Samuel Gougeon a écrit :
>>>>> Hello Stéphane,
>>>>>
>>>>> Le 17/01/2019 à 08:37, Stéphane Mottelet a écrit :
>>>>>> Hello Samuel,
>>>>>>
>>>>>> I have initially voted for this behavior (sparse([]) == (  0,  0) 
>>>>>> zero sparse matrix ) but your remark on numerous occurences of 
>>>>>> "sparse([])" in scilab prevented to do so.
>>>>>
>>>>> Why? My remark aimed to bring the attention to existing 
>>>>> occurrences and to prevent merging the commit without updating 
>>>>> them, not to prevent updating them.
>>>>> Then these occurrences changed your opinion and vote, not mine.
>>>>>
>>>>> Best regards
>>>>> Samuel
>>>>
>>>> Please see comment #8:
>>>>
>>>> Anyway, *as bug #15758 is not related to sparse([]) being not 
>>>> sparse*, and considered the numerous side effects, I will restore 
>>>> sparse([]) == double empty matrix. *If you find necessary to have 
>>>> sparse([]) == sparse empty matrix, please file a bug/whish on BZ.*
>>>>
>>>
>>> Yes, and neither you -- that voted for it -- nor me did it.
>>> And finally we agree: keeping sparse([])==[] was your decision.
>>> Changing this could be done later if it proves to be better.
>>> For the time being, the situation is the following:
>>>
>>> *Scilab 6.0.1*:
>>> --> sparse([])
>>>  ans  =
>>>     []
>>>
>>> --> sparse([],[])
>>>  ans  =
>>> (  0,  0) zero sparse matrix
>>>
>>> --> sparse([],[],[0,2])
>>>  ans  =
>>>     []
>>>
>>> *Scilab 6.0.2-* after https://codereview.scilab.org/20492 :
>>> --> sparse([])      // unchanged
>>>  ans  =
>>>     []
>>>
>>> --> sparse([],[])   // unchanged
>>>  ans  =
>>> (  0,  0) zero sparse matrix
>>>
>>> --> sparse([],[],[0,2])  // *CHANGED*
>>>  ans  =
>>> (  0,  0) zero sparse matrix
>>>
>>> while i don't think that this last change is intentional.
>>
>> it is. To me,
>>
>> sparse([],[]) <=> sparse([],[],[0,0]) by getting dims implicitely 
>> defined in first two arguments (ij,v), so explicit size definition in 
>> sparse([],[],[2,0]) should give the same output
>>
>
> Yes
>
>> (2x0 == empty matrix);
>>
>
> No. Since both other syntaxes yielded [], [] should be returned. What 
> would make a consistent answer for *all* empty inputs.

I mean: Changing

--> sparse([],[])
  ans  =
(  0,  0) zero sparse matrix

into

--> sparse([],[])
  ans  =
    []

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