static double[] addVector(double[] x, double[] y, double c, double[] reuse) {
    if (reuse == null) {
      reuse = new double[x.length];
    }
    for (int i = 0; i < x.length; i++) {
      reuse[i] = x[i] + c * y[i];
    }
    return reuse;
  }
static double [ ] addVector ( double [ ] x , double [ ] y , double c , double [ ] reuse ) { if ( reuse == null ) { reuse = new double [ x . length ] ; } for ( int i = 0 ; i < x . length ; i ++ ) { reuse [ i ] = x [ i ] + c * y [ i ] ; } return reuse ; }
Performs x + cy