 LAPACK 3.11.0 LAPACK: Linear Algebra PACKage
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## ◆ zdrot()

 subroutine zdrot ( integer N, complex*16, dimension( * ) ZX, integer INCX, complex*16, dimension( * ) ZY, integer INCY, double precision C, double precision S )

ZDROT

Purpose:
``` Applies a plane rotation, where the cos and sin (c and s) are real
and the vectors cx and cy are complex.
jack dongarra, linpack, 3/11/78.```
Parameters
 [in] N ``` N is INTEGER On entry, N specifies the order of the vectors cx and cy. N must be at least zero.``` [in,out] ZX ``` ZX is COMPLEX*16 array, dimension at least ( 1 + ( N - 1 )*abs( INCX ) ). Before entry, the incremented array ZX must contain the n element vector cx. On exit, ZX is overwritten by the updated vector cx.``` [in] INCX ``` INCX is INTEGER On entry, INCX specifies the increment for the elements of ZX. INCX must not be zero.``` [in,out] ZY ``` ZY is COMPLEX*16 array, dimension at least ( 1 + ( N - 1 )*abs( INCY ) ). Before entry, the incremented array ZY must contain the n element vector cy. On exit, ZY is overwritten by the updated vector cy.``` [in] INCY ``` INCY is INTEGER On entry, INCY specifies the increment for the elements of ZY. INCY must not be zero.``` [in] C ``` C is DOUBLE PRECISION On entry, C specifies the cosine, cos.``` [in] S ``` S is DOUBLE PRECISION On entry, S specifies the sine, sin.```

Definition at line 97 of file zdrot.f.

98*
99* -- Reference BLAS level1 routine --
100* -- Reference BLAS is a software package provided by Univ. of Tennessee, --
101* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
102*
103* .. Scalar Arguments ..
104 INTEGER INCX, INCY, N
105 DOUBLE PRECISION C, S
106* ..
107* .. Array Arguments ..
108 COMPLEX*16 ZX( * ), ZY( * )
109* ..
110*
111* =====================================================================
112*
113* .. Local Scalars ..
114 INTEGER I, IX, IY
115 COMPLEX*16 CTEMP
116* ..
117* .. Executable Statements ..
118*
119 IF( n.LE.0 )
120 \$ RETURN
121 IF( incx.EQ.1 .AND. incy.EQ.1 ) THEN
122*
123* code for both increments equal to 1
124*
125 DO i = 1, n
126 ctemp = c*zx( i ) + s*zy( i )
127 zy( i ) = c*zy( i ) - s*zx( i )
128 zx( i ) = ctemp
129 END DO
130 ELSE
131*
132* code for unequal increments or equal increments not equal
133* 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 i = 1, n
142 ctemp = c*zx( ix ) + s*zy( iy )
143 zy( iy ) = c*zy( iy ) - s*zx( ix )
144 zx( ix ) = ctemp
145 ix = ix + incx
146 iy = iy + incy
147 END DO
148 END IF
149 RETURN
150*
151* End of ZDROT
152*
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