There is no really good way to do this now. I will enter an enhancement request.

–Loren

Is there any way to do this? to cause an error to occur in the caller?

thanks much,

I would recommend reading up on MExceptions (which weren’t available when I wrote this post). Also, check out throw (and maybe rethrow or throwAsCaller) which allows some control of the stack.

–Loren

What I have tried to do was:

(start of code snippet)

switch error_type
case 1
error_text=’??? Some error text’;
case 2
error_text=’??? Some error text’;
…
end

%Make the error structure that will be displayed.
serror=struct(‘message’, error_text, ‘identifier’, ”,…
‘stack’, struct(‘file’, ”, ‘name’, ‘Standard Structure’, ‘line’, 1));

%Throw the actual error.
error(serror);

(end of code snippet)

On my computer at work, the code does what I want it to do. But, when I try it at home, the stack information is still being displayed when I use the error function.

Is there some kind of setting that needs to be set?

I’ve even tried:

dbstack=struct(‘file’, ”, ‘name’, ‘Standard Structure’, ‘line’, 1);

serror=struct(‘message’, error_text, ‘identifier’, ”,…
‘stack’, dbstack);

but I get the same problem.

Any ideas?

There is no analogous try-catch way to catch a warning. You would need to interrogate using the lastwarn function just after you issue the command that might warn.

–Loren

Ken, you are right, this is what I want. In essence I’d like
to write out to a file the calling parameters of a function,
from within the function itself.

Ken’s suggestion is a good one, I checked inputname, and it
“almost” does what I want… The problem is that I get the
name of the variable in the caller’s space, and if it’s an
evaluated expression I get nothing at all.

What I’d really really like would be the evaluated arguments that the function got when it was called…
I think i can explain that as a kind of “stack trace”.
For example, if I use,

function myplot(x,varargin)
plot(x,varargin{:})
magic_argument_printing_to_file_command;
return

then when I call myplot as,

myplot(sin(0:.1:1),’color’,[.5 .7 .3],’linestyle’,':’)

I’d like to see this written out to a file,
calling parameters for function MYPLOT =>
sin(0:.1:1)
‘color’
[.5 .7 .3]
‘linestyle’
‘:’
Now, assuming that sin(0:.1:1) has already been evaluated within myplot(), i still would find it useful to have the
actual vector written to the file, so that I could recompute all function calls a posteriori…

Loren’s suggestion is interesting, but won’t help me here, I think.

Thanks for any suggestion!

It sounds to me like you want to know what args were used by the caller, but from inside the called function. If so, you can use inputname, a built-in matlab function, inside the calling function.

-Ken

It would be nice if MATLAB had a more natural way for you to find out the argument list. For now, you can try this:

dbtype yourfunction 1

will show you the first line of the M-file. If it’s the usual function line, you can see the argument list there.

–Loren

Putting it another way, how do I access the arguments of a function call in matlab as a string, without knowing a priori the type/number of the parameters ? I’d like to record in a file the calling argv (argument vector) for every function call, so that I can try to find problems with some optimization results, where things diverge long after some function was called with erroneous values…

dbstack returns a structure that *almost* has what I need…

I hope someone reading this blog can make me a size matlab programmer!