Re: Testing for function handles

[Juan Pablo Carbajal]

On Wed, Nov 9, 2011 at 9:18 AM, Dr. Alexander Klein
<address@hidden> wrote:
> Good morning,
>
> is there any preferred way to check whether a given parameter or variable 
> contains a function handle?
>
> I find myself strcmp'ing the result of typeinfo quite often, but this is 
> really clumsy. Then again, ishandle only checks for graphics handles ...
>
> Best regards,
>
>        Alex
>
> --
>          Dr. Alexander Klein, Diplom-Mathematiker
>
> Physiologisches Institut       |               TransMIT Zentrum
> Raum 543                       |        für Numerische Methoden
> Aulweg 129                     |          Heinrich-Buff-Ring 44
> 35392 Giessen                  |                  35392 Giessen
>
>

Running
grep -i -r --exclude-dir=".hg" --include="*.cc" function_handle .

in the root of octave repository you will see that octave_values
already have a field is_function_handle that can be used to check if
they are function handles at C++ level.
Would be a matter of creating a DEFUN to return the value of that
field to get the functionality at interpreter level (I just can't find
that implemented, my apologies if it is) as is done, for example, in
src/strfns.cc line 297

You can use
!isnumeric(f) && (check that is not any non-numeric classes)

but is much slower than strcmp(typeinfo(f),"function_handle") or
strcmp(class(f),"function_handle")

my two cents.


-- 
M. Sc. Juan Pablo Carbajal
-----
PhD Student
University of Zürich
http://ailab.ifi.uzh.ch/carbajal/