#include "mex.h"

void
mexFunction (int nlhs, mxArray* plhs[], int nrhs, 
             const mxArray* prhs[])
{
  mwIndex i;
  mwSize n;
  double *vri, *vro;
  
  if (nrhs != 1 || ! mxIsNumeric (prhs[0]))
    mexErrMsgTxt ("expects matrix");

  n = mxGetNumberOfElements (prhs[0]);
  plhs[0] = (mxArray *) mxCreateNumericArray 
    (mxGetNumberOfDimensions (prhs[0]),
     mxGetDimensions (prhs[0]), mxGetClassID (prhs[0]),
     mxIsComplex (prhs[0]));
  vri = mxGetPr (prhs[0]);
  vro = mxGetPr (plhs[0]);

  if (mxIsComplex (prhs[0]))
    {
      double *vii, *vio;
      vii = mxGetPi (prhs[0]);
      vio = mxGetPi (plhs[0]);

      for (i = 0; i < n; i++)
        {
          vro [i] = vri [i] * vri [i] - vii [i] * vii [i];
          vio [i] = 2 * vri [i] * vii [i];
        }
    }
  else
    {
      for (i = 0; i < n; i++)
        vro [i] = vri [i] * vri [i];
    }
}