Re: How do you pass two Octave functions to an .oct function?

[David Grundberg]

babelproofreader skrev:
> > I'd think these messages are pretty understandable.
> > You simply can't pass a raw double * pointer (the local buffer) to
> > feval, because it can't handle it. You need to create a valid
> > octave_value from it. Declare rolling_vector as ColumnVector and it
> > will likely work.
> >     
>
> I have stripped my code down to the bare minimum, declared the input as
> ColumnVector, and it still fails on compile. My revised code is 
>
> #include <octave/oct.h>
> #include <octave/dColVector.h>
> #include <octave/parse.h>
>      
> DEFUN_DLD (rollingfft, args, , "Help String")
> {
> octave_value_list retval;
> octave_value_list fft_result_vector;
> octave_value_list ifft_result_vector;
> octave_value_list real_result_vector;
>
>  octave_function *fcn1 = args(0).function_value ();                               
> // supply Octave "fft" function
>  octave_function *fcn2 = args(1).function_value ();                               
> // supply Octave "ifft" function
>  octave_function *fcn3 = args(2).function_value ();                               
> // supply Octave "real" function
>  ColumnVector input_vector = args(3).column_vector_value ();
>  ColumnVector output_vector = args(3).column_vector_value ();
>
>  fft_result_vector = feval( fcn1 , input_vector );
>  ifft_result_vector = feval( fcn2 , fft_result_vector ); 
>  real_result_vector = feval( fcn3 , ifft_result_vector );
>  retval = real_result_vector;                                                                        
>
> return retval;                                                                       
> }
>
> and the error message is 
>
> octave:1> mkoctfile rollingfft.cc
> rollingfft.cc: In function ‘octave_value_list Frollingfft(const
> octave_value_list&, int)’:
> rollingfft.cc:18: error: no matching function for call to
> ‘feval(octave_function*&, ColumnVector&)’
> /usr/include/octave-3.0.1/octave/parse.h:118: note: candidates are:
> octave_value_list feval(const std::string&, const octave_value_list&, int)
> /usr/include/octave-3.0.1/octave/parse.h:123: note:                
> octave_value_list feval(octave_function*, const octave_value_list&, int)
> /usr/include/octave-3.0.1/octave/parse.h:126: note:                
> octave_value_list feval(const octave_value_list&, int)
>  
>   

I don't understand under which circumstances you'd want to replace the 
fourier transform functions. Passing the functions like arguments makes 
me suspect you haven't looked at the API. Also, naming a variable of 
type octave_value_list "vector" is confusing, so I removed that.

Have you tried implementing this in Octave code (.m)?


#include <octave/oct.h>
#include <octave/dColVector.h>
#include <octave/parse.h>

DEFUN_DLD (rollingfft, args, , "Help String")
{
 octave_value_list retval;
 octave_value_list fft_result;
 ComplexColumnVector freq_rep;
 octave_value_list ifft_result;
 octave_value_list real_result;

 fft_result = feval ("fft", args (0), 1);
 freq_rep = fft_result (0).complex_column_vector_value ();
 ifft_result = feval ("ifft", octave_value (freq_rep), 1);
 real_result = feval ("real", ifft_result, 1);
 retval = real_result;

 return retval;
}