# csrot.f

          SUBROUTINE CSROT (N, CX, INCX, CY, INCY, C, S)
    C***BEGIN PROLOGUE  CSROT
    C***PURPOSE  Apply a plane Givens rotation.
    C***LIBRARY   SLATEC (BLAS)
    C***CATEGORY  D1B10
    C***TYPE      COMPLEX (SROT-S, DROT-D, CSROT-C)
    C***KEYWORDS  BLAS, GIVENS ROTATION, GIVENS TRANSFORMATION,
    C             LINEAR ALGEBRA, PLANE ROTATION, VECTOR
    C***AUTHOR  Dongarra, J., (ANL)
    C***DESCRIPTION
    C
    C     CSROT applies the complex Givens rotation
    C
    C          (X)   ( C S)(X)
    C          (Y) = (-S C)(Y)
    C
    C     N times where for I = 0,...,N-1
    C
    C          X = CX(LX+I*INCX)
    C          Y = CY(LY+I*INCY),
    C
    C     where LX = 1 if INCX .GE. 0, else LX = 1+(1-N)*INCX, and LY is
    C     defined in a similar way using INCY.
    C
    C     Argument Description
    C
    C        N      (integer)  number of elements in each vector
    C
    C        CX     (complex array)  beginning of one vector
    C
    C        INCX   (integer)  memory spacing of successive elements
    C               of vector CX
    C
    C        CY     (complex array)  beginning of the other vector
    C
    C        INCY   (integer)  memory spacing of successive elements
    C               of vector CY
    C
    C        C      (real)  cosine term of the rotation
    C
    C        S      (real)  sine term of the rotation.
    C
    C***REFERENCES  J. J. Dongarra, J. R. Bunch, C. B. Moler, and G. W.
    C                 Stewart, LINPACK Users' Guide, SIAM, 1979.
    C***ROUTINES CALLED  (NONE)
    C***REVISION HISTORY  (YYMMDD)
    C   810223  DATE WRITTEN
    C   890831  Modified array declarations.  (WRB)
    C   890831  REVISION DATE from Version 3.2
    C   891214  Prologue converted to Version 4.0 format.  (BAB)
    C   920310  Corrected definition of LX in DESCRIPTION.  (WRB)
    C   920501  Reformatted the REFERENCES section.  (WRB)
    C***END PROLOGUE  CSROT