On Sun, Mar 21, 2010 at 10:28 AM, David Bateman <[email protected]> wrote:
> Michael Creel wrote:
>> Internally, __bfgsmin.c uses feval to compute the function value. Perhaps
>> that could be changed to work with anonymous functions. I think that this
>> would be the hardest part of making the change.
>>
>>
> Here is a code snippet that is needed to accept a function as the first
> argument in an oct-file as a function handle or inline functio. String
> functions are accepted and converted internally into an anonymous
> function handle. The code then calls the function on an internally
> created list of arguments and gets the results in another
> octave_value_list.. If a string was passed, the internally created
> function handle is cleared when you leave the oct-file..
>
>
> octave_function *opt_fcn;
> std::string fcn_name;
>
> .....
>
> if (args(0).is_function_handle () || args(0).is_inline_function ())
> opt_fcn = args(0).function_value ();
Using function_value on a function handle is not the best idea,
because that will ignore overloads of a named handle. It is better to
call directly do_multi_index_op on the octave_value holding the
handle. This works on inline functions, too.
> else
> {
> fcn_name = unique_symbol_name ("__opt_fcn_");
> std::string fname = "function y = ";
> fname.append (fcn_name);
> fname.append ("(x) y = ");
> opt_fcn = extract_function (args(0), "mle_estimate", fcn_name,
> fname,
> "; endfunction");
> }
>
> .....
>
> octave_value_list in_args;
> in_args(0) = x;
> octave_value_list out_args = opt_fcn->do_multi_index_op (1, in_args);
>
> ....
>
> if (fcn_name.length ())
> clear_unction (fcn_name);
>
I'd advise against doing this at all. It is not a good idea to inject
identifiers into function scope, as these can potentially confuse you,
and you may forget to clear them up. Besides, it will only allow a
single parameter named x, and will conflict if you also want to allow
passing a function name. I suggest you only allow the latter, and
simply look up the function through the symbol table. Passing the body
as a string has no advantages whatsoever over anonymous functions.
Regarding the use of function_value, I advise you against doing it
unless necessary and just work directly with octave_values instead.
--
RNDr. Jaroslav Hajek, PhD
computing expert & GNU Octave developer
Aeronautical Research and Test Institute (VZLU)
Prague, Czech Republic
url: www.highegg.matfyz.cz
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