Re: A question about programming using dynamically linked function

[Paul Thomas]

Find below a slightly different approach to David's.  Like David the 
Array<T> function fortran_vec() is used to point to the first member in 
the complexMatrix.  However, my example uses the C++ standard library 
complex, rather than the octave Complex.  I have commented out a 
transpose that operates directly on the complex matrices and replaced it 
in the next line with the same operation using complex pointers.

Best regards

Paul T

#include <octave/oct.h>
#include <octave/quit.h>
#include <complex>
typedef std::complex<double> dComplex;
DEFUN_DLD (complexdemo, args, ,
"Demonstrate fortran_vec for complex \n\n\
transpose_of_x=complexdemo(x) \n") {
 if ( args.length() !=  1 ) {
   error("this version of matrixdemo omly takes one argument");
   return octave_value( 0 );
 }
 ComplexMatrix xin1( args(0).complex_matrix_value() );
 int ir = xin1.rows();
 int ic = xin1.cols();
 ComplexMatrix xout1(ic,ir);
 dComplex *pin1 = xin1.fortran_vec();
 dComplex *pout1 = xout1.fortran_vec();
 for (int ir1 = 0 ; ir1 < ir ; ir1++)
   for (int ic1 = 0 ; ic1 < ic ; ic1++) {
//      xout1(ic1,ir1) = xin1(ir1,ic1);                //transpose using 
Matrices
      pout1[ic1 + ir1*ic] = pin1[ir1 + ic1*ir];       //transpose using 
pointers
   }
 return octave_value( xout1 );
}  



address@hidden wrote:

> Hi
>
> I am writing dynamically linked functions. In my function, I
> need to copy the data from a complex matrix (in octave_value
> type) to a double buffer. I was wondering if there is a way to
> find a pointer to the real data in the complex matrix (in
> octave_value type), so that I can use memcpy to copy it to my
> own buffer. The similar function can be found in MATLAB which
> is mxGetPr. Does Octave have similar functions like mxGetPr?
>
> Thanks a lot!
>
> Jia
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