Re: Need test run in Matlab

[John W. Eaton]

On 1/29/19 2:39 PM, Christian Himpe wrote:
> Here is the output of the corrected script.

Thanks.

I'm a bit confused by these results.  Maybe I'm missing something, but I 
don't understand the case of f3(1), which shows that "sigma -1" is 
evaluated as a command.  Compare this with f1(), which fails when there 
is a variable in the local workspace that conflicts with the name of the 
function (sigma).  How does that make sense?

Functions:

function f1 ()
  sigma = svd (1);
  eval ('sigma -1;');
end

function f3 (sigma)
  eval ('sigma -1;');
end

function r = sigma (opt)
  global sigma_call;
  if (nargin == 0)
    sigma_call = 'function';
    r = 1;
  elseif (ischar (opt))
    sigma_call = 'command';
    r = 1;
  else
    sigma_call = 'unexpected';
  end
end

Output you sent for calling f1() and f3(1):

f1: error: Error using f1 (line 3)
Error: "sigma" was previously used as a variable, conflicting with its 
use here as the name of a function or command.
See "How MATLAB Recognizes Command Syntax" in the MATLAB documentation 
for details.
f1 (): none

f3 (1): command

Here are the functions:

function f1 ()
  sigma = svd (1);
  eval ('sigma -1;');
end

function f3 (sigma)
  eval ('sigma -1;');
end

function r = sigma (opt)
  global sigma_call;
  if (nargin == 0)
    sigma_call = 'function';
    r = 1;
  elseif (ischar (opt))
    sigma_call = 'command';
    r = 1;
  else
    sigma_call = 'unexpected';
  end
end

Why should f3(1) succeed in calling sigma as a command-style function 
when f1() fails with an error message about sigma defined as a variable 
and later being used as a command-style function?  Isn't sigma defined 
as a variable in both cases prior to the use as a function?

jwe