praat/external/gsl/gsl_cblas__source_rotm.h

/* blas/source_rotmg.h
 * 
 * Copyright (C) 1996, 1997, 1998, 1999, 2000, 2007 Brian Gough
 * 
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or (at
 * your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 */

{
  INDEX n;
  INDEX i = OFFSET(N, incX);
  INDEX j = OFFSET(N, incY);

  BASE h11, h21, h12, h22;

  if (P[0] == -1.0) {
    h11 = P[1];
    h21 = P[2];
    h12 = P[3];
    h22 = P[4];
  } else if (P[0] == 0.0) {
    h11 = 1.0;
    h21 = P[2];
    h12 = P[3];
    h22 = 1.0;
  } else if (P[0] == 1.0) {
    h11 = P[1];
    h21 = -1.0;
    h12 = 1.0;
    h22 = P[4];
  } else if (P[0] == -2.0) {
    return;
  } else {
    BLAS_ERROR("unrecognized value of P[0]");
    return;
  }

  for (n = 0; n < N; n++) {
    const BASE w = X[i];
    const BASE z = Y[j];
    X[i] = h11 * w + h12 * z;
    Y[j] = h21 * w + h22 * z;
    i += incX;
    j += incY;
  }

}