Comments on: Convenient nargout Behavior

By: OysterEngineer

OysterEngineer — Tue, 17 Nov 2009 22:39:24 +0000

That helps some. I see how the numel([c{1:0}0] is 0.

But, I haven’t been able to invent a function, f, with no outputs such that nargout(’f') or nargout(@f)is also 0. I keep getting -1.

By: Loren

Loren — Tue, 17 Nov 2009 19:24:32 +0000

OysterEngineer-

When MATLAB goes to calcualate [c{1:0}] = f(…),
it is finding 0 elements on the left side (numel([c{1:0}]) IS 0) which IS nargout(f), and therefore f gets called as if nargout is 0.

–Loren

By: OysterEngineer

OysterEngineer — Tue, 17 Nov 2009 19:18:49 +0000

I understand that 1:0 is an empty matrix.

But, by what is happening with [c{1:0}] = f(…)

Is it really doing something like: [c{1:0}] = [] ?

Also, what do you mean when you say, “when called with an nargout is zero . . . ?” The FRP is nicely clear in explaining that it can be called without an input argument to return the number of output arguments a user has supplied. Or, it can be called with a function handle or a function name as an input argument to return the number of output arguments the function was written to provide. So, which use are you referring to?

By: Loren

Loren — Fri, 24 Apr 2009 16:35:23 +0000

I’m delighted that several of you find good use in this nargout behavior.

–Loren

By: Kieran

Kieran — Thu, 23 Apr 2009 15:13:14 +0000

Thanks Loren. This code really helped me in using subsref in my classes. I wanted to only change some subsref functionality and call the builtin version for the rest, but ran into output argument issues. I ended up doing something like:

function varargout = subsref(this, s)
use_built_in = true;
% Add custom subsref here and set use_built_in to false.

% Use default subsref for others.
if use_built_in
[varargout{1:nargout}] = builtin(’subsref’, this, s);
end
end

By: Sung Soo

Sung Soo — Tue, 21 Apr 2009 00:35:06 +0000

I use similar technique to access subfunctions because I don’t want to have many small functions in different m-files though ‘class’ can solve this too.

By: Oliver Woodford

Oliver Woodford — Wed, 15 Apr 2009 15:41:46 +0000

Useful. It allowed me to change:

str = sprintf('"%s" %s', xpdf_path, cmd);
if nargout
    [varargout{:}] = system(str);
else
    system(str);
end

to:

[varargout{1:nargout}] = system(sprintf('"%s" %s', xpdf_path, cmd));

Oliver