Matlab Bug? cell array of containers.Map

I have two expressions. In my opinion, both are equal. But one works, the other causes a matlab error.

for your info: obj.TabData is a 2×1 cell array [103×1 containers.Map] [163×1 containers.Map]

expression 1)

mapObj = obj.TabData{1}

causes "Expected one output from a curly brace or dot indexing expression, but there were 3 results."

expression 2)

temp = obj.TabData;
mapObj = temp{1};

works. mapObj is Map with properties: Count: 103 KeyType: char ValueType: any afterwards.

Is this a Matlab Bug? Or can anyone explain this behavior, please?

Answer 1

[Stephen23]

"In my opinion, both are equal"

They aren't.

"Is this a Matlab Bug?"

No.

"Or can anyone explain this behavior, please?"

https://www.mathworks.com/help/matlab/matlab_prog/comma-separated-lists.html

https://www.mathworks.com/matlabcentral/answers/320713-how-to-operate-on-comma-separated-lists

Your code does what I would expect if obj was not scalar. Basically you are doing this:

>> obj = struct('blah',{{1,1},{2,2},{3,3}})
obj = 
1x3 struct array with fields:
    blah
>> x = obj.blah{1} % cell indexing into comma-separated list -> error
Field reference for multiple structure elements that is followed by more reference blocks is an error. 
>> x = obj.blah % take first output of comma-separated list -> no error
x = 
    [1]    [1]
>> x{1}
ans =
     1

Read this to know why the second example works:

https://www.mathworks.com/matlabcentral/answers/344486-generate-comma-separated-list-in-single-line-of-code

[Christian Stöhr]

Thank you very much!