[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: how to define a function handle in oct-files

From: Evan
Subject: Re: how to define a function handle in oct-files
Date: Fri, 11 Jan 2008 22:36:36 +0800

On Jan 10, 2008 9:24 PM, Evan <address@hidden> wrote:
> I want to define a function like the following in an oct-file
> function y=fun(f)
>   g=@(x) 1./f(x);
>   y=quad(g, 0, 1);
> endfunction
> what should I write for the sentence "g=@(x) 1./f(x);"?
> thanks in advance

I still don't know if there is any standard method to do this, but
after look through the head files of Octave, I figure out a way as

      octave_value_list f = feval("func2str", args(0), 1);
      std::string fcn = f(0).string_value ();
      std::string newfcn = "@(x) 1./( (" + fcn + ")(x))";
      int status;
      octave_value_list nf = eval_string (newfcn, true, status, 1);

in "parse.h"
     extern OCTINTERP_API octave_value_list
     eval_string (const std::string&, bool silent, int& parse_status,
int hargout);
I think "hargout" is a typo for "nargout". I wonder what is
"parse_status" for. It seems that it is always zero whether the string
is evaluated successfully or not.

ps. When trying these things, I encounter another thing I don't understand i.e.

octave:1> @(x) 1./( (@(y) 1./y) (x) )
ans =

@(x) 1 ./ ((@(y) 1 ./ y;
) (x))

octave:2> func2str(  @(x) 1./( (@(y) 1./y) (x) )  )
ans = @(x) 1 ./ ((@(y) 1 ./ y;
) (x))

Why there are semicolons in the output?

reply via email to

[Prev in Thread] Current Thread [Next in Thread]