W = evalin('caller','who global') returns an error

The command

evalin('caller','who global')

correctly returns the global variables in the caller workspace, but

W = evalin('caller','who global')

returns the error message

Error: illegal use of the reserved keyword global

Yet the syntax of the line that throws the error is consistent with the prescribed use of evalin. Is this a bug? What's the workaround? Thanks

[Steven Lord]

That code is basically equivalent to running this code in the caller's workspace.

W = who global

You can't use command form when you want to get an output argument from the function that you're calling.

Walter has shown you one way to perform this call. But in general, both evalin and global are discouraged. Can you say a little more about why your function is reaching up into its caller's workspace and why you're using global variables? We may be able to offer some alternatives.

[Leo Simon]

Thanks Steven, here's an mwe, illustrating how I use the evalin syntax. I have decades of globals scattered all over the place, and backward compatibility means that I need a solution (Walter's works perfectly well). But if you have suggestions about alternatives to my use of evalin, I'd be most interested in hearing them.

function parent
global delta
child('gamma',5,'delta',6);

function child(varargin);
W = evalin('caller','who("global")');
for ii=1:2:numel(varargin);
	Variable	= varargin{ii};
	if ~isempty(strmatch(W,Variable));
		disp([ Variable ' is a global variable but you passed it as an argument to varargin; don''t do that']);
		keyboard;
	end;
end

[Walter Roberson]

I would disagree on that checking. You want to encourage migration to passing variables as parameters, to reduce the reliance on global variables.

Answer 1

[Walter Roberson]

W = evalin('caller','who("global")')