Empty array gets added to. (Or not)

Andr? — Fri, 16 Oct 2009 09:56:03 -0400

Hi.

I discovered that

a=[];
b=4;
a=a+b;

will not yield an error message as would

a = a+4;

(without first assigning a). Yet it also does not give a=4... I knew that Nan+4 =NaN, but why is []+4=[] ? Is there more 'black hole beahviour' i should know about?

Thank you.

Andr

Re: Empty array gets added to. (Or not)

Loren Shure — Fri, 16 Oct 2009 12:05:29 -0400

In article <hb9fvj$i37$1@fred.mathworks.com>, bukwyrm@googlemail.com
says...
> Hi.
>
> I discovered that
>
> a=[];
> b=4;
> a=a+b;
>
> will not yield an error message as would
>
> a = a+4;
>
> (without first assigning a). Yet it also does not give a=4... I knew that Nan+4 =NaN, but why is []+4=[] ? Is there more 'black hole beahviour' i should know about?
>
> Thank you.
>
> Andr
>

b is a scalar and MATLAB addition adheres to the scalar expansion rule,
i.e., anything + scalar is size of anything. Hence you get empty as the
output for a in your example.

--
Loren
http://blogs.mathworks.com/loren

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Empty array gets added to. (Or not)

Re: Empty array gets added to. (Or not)