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    1: *> \brief \b ZROT applies a plane rotation with real cosine and complex sine to a pair of complex vectors.
    2: *
    3: *  =========== DOCUMENTATION ===========
    4: *
    5: * Online html documentation available at
    6: *            http://www.netlib.org/lapack/explore-html/
    7: *
    8: *> \htmlonly
    9: *> Download ZROT + dependencies
   10: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/zrot.f">
   11: *> [TGZ]</a>
   12: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/zrot.f">
   13: *> [ZIP]</a>
   14: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/zrot.f">
   15: *> [TXT]</a>
   16: *> \endhtmlonly
   17: *
   18: *  Definition:
   19: *  ===========
   20: *
   21: *       SUBROUTINE ZROT( N, CX, INCX, CY, INCY, C, S )
   22: *
   23: *       .. Scalar Arguments ..
   24: *       INTEGER            INCX, INCY, N
   25: *       DOUBLE PRECISION   C
   26: *       COMPLEX*16         S
   27: *       ..
   28: *       .. Array Arguments ..
   29: *       COMPLEX*16         CX( * ), CY( * )
   30: *       ..
   31: *
   32: *
   33: *> \par Purpose:
   34: *  =============
   35: *>
   36: *> \verbatim
   37: *>
   38: *> ZROT   applies a plane rotation, where the cos (C) is real and the
   39: *> sin (S) is complex, and the vectors CX and CY are complex.
   40: *> \endverbatim
   41: *
   42: *  Arguments:
   43: *  ==========
   44: *
   45: *> \param[in] N
   46: *> \verbatim
   47: *>          N is INTEGER
   48: *>          The number of elements in the vectors CX and CY.
   49: *> \endverbatim
   50: *>
   51: *> \param[in,out] CX
   52: *> \verbatim
   53: *>          CX is COMPLEX*16 array, dimension (N)
   54: *>          On input, the vector X.
   55: *>          On output, CX is overwritten with C*X + S*Y.
   56: *> \endverbatim
   57: *>
   58: *> \param[in] INCX
   59: *> \verbatim
   60: *>          INCX is INTEGER
   61: *>          The increment between successive values of CX.  INCX <> 0.
   62: *> \endverbatim
   63: *>
   64: *> \param[in,out] CY
   65: *> \verbatim
   66: *>          CY is COMPLEX*16 array, dimension (N)
   67: *>          On input, the vector Y.
   68: *>          On output, CY is overwritten with -CONJG(S)*X + C*Y.
   69: *> \endverbatim
   70: *>
   71: *> \param[in] INCY
   72: *> \verbatim
   73: *>          INCY is INTEGER
   74: *>          The increment between successive values of CY.  INCX <> 0.
   75: *> \endverbatim
   76: *>
   77: *> \param[in] C
   78: *> \verbatim
   79: *>          C is DOUBLE PRECISION
   80: *> \endverbatim
   81: *>
   82: *> \param[in] S
   83: *> \verbatim
   84: *>          S is COMPLEX*16
   85: *>          C and S define a rotation
   86: *>             [  C          S  ]
   87: *>             [ -conjg(S)   C  ]
   88: *>          where C*C + S*CONJG(S) = 1.0.
   89: *> \endverbatim
   90: *
   91: *  Authors:
   92: *  ========
   93: *
   94: *> \author Univ. of Tennessee
   95: *> \author Univ. of California Berkeley
   96: *> \author Univ. of Colorado Denver
   97: *> \author NAG Ltd.
   98: *
   99: *> \ingroup complex16OTHERauxiliary
  100: *
  101: *  =====================================================================
  102:       SUBROUTINE ZROT( N, CX, INCX, CY, INCY, C, S )
  103: *
  104: *  -- LAPACK auxiliary routine --
  105: *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
  106: *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
  107: *
  108: *     .. Scalar Arguments ..
  109:       INTEGER            INCX, INCY, N
  110:       DOUBLE PRECISION   C
  111:       COMPLEX*16         S
  112: *     ..
  113: *     .. Array Arguments ..
  114:       COMPLEX*16         CX( * ), CY( * )
  115: *     ..
  116: *
  117: * =====================================================================
  118: *
  119: *     .. Local Scalars ..
  120:       INTEGER            I, IX, IY
  121:       COMPLEX*16         STEMP
  122: *     ..
  123: *     .. Intrinsic Functions ..
  124:       INTRINSIC          DCONJG
  125: *     ..
  126: *     .. Executable Statements ..
  127: *
  128:       IF( N.LE.0 )
  129:      $   RETURN
  130:       IF( INCX.EQ.1 .AND. INCY.EQ.1 )
  131:      $   GO TO 20
  132: *
  133: *     Code for unequal increments or equal increments not equal to 1
  134: *
  135:       IX = 1
  136:       IY = 1
  137:       IF( INCX.LT.0 )
  138:      $   IX = ( -N+1 )*INCX + 1
  139:       IF( INCY.LT.0 )
  140:      $   IY = ( -N+1 )*INCY + 1
  141:       DO 10 I = 1, N
  142:          STEMP = C*CX( IX ) + S*CY( IY )
  143:          CY( IY ) = C*CY( IY ) - DCONJG( S )*CX( IX )
  144:          CX( IX ) = STEMP
  145:          IX = IX + INCX
  146:          IY = IY + INCY
  147:    10 CONTINUE
  148:       RETURN
  149: *
  150: *     Code for both increments equal to 1
  151: *
  152:    20 CONTINUE
  153:       DO 30 I = 1, N
  154:          STEMP = C*CX( I ) + S*CY( I )
  155:          CY( I ) = C*CY( I ) - DCONJG( S )*CX( I )
  156:          CX( I ) = STEMP
  157:    30 CONTINUE
  158:       RETURN
  159:       END