slctes.f

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*> \brief \b SLCTES
*
*  =========== DOCUMENTATION ===========
*
* Online html documentation available at
*            http://www.netlib.org/lapack/explore-html/
*
*  Definition:
*  ===========
*
*       LOGICAL          FUNCTION SLCTES( ZR, ZI, D )
*
*       .. Scalar Arguments ..
*       REAL               D, ZI, ZR
*       ..
*
*
*> \par Purpose:
*  =============
*>
*> \verbatim
*>
*> SLCTES returns .TRUE. if the eigenvalue (ZR/D) + sqrt(-1)*(ZI/D)
*> is to be selected (specifically, in this subroutine, if the real
*> part of the eigenvalue is negative), and otherwise it returns
*> .FALSE..
*>
*> It is used by the test routine SDRGES to test whether the driver
*> routine SGGES successfully sorts eigenvalues.
*> \endverbatim
*
*  Arguments:
*  ==========
*
*> \param[in] ZR
*> \verbatim
*>          ZR is REAL
*>          The numerator of the real part of a complex eigenvalue
*>          (ZR/D) + i*(ZI/D).
*> \endverbatim
*>
*> \param[in] ZI
*> \verbatim
*>          ZI is REAL
*>          The numerator of the imaginary part of a complex eigenvalue
*>          (ZR/D) + i*(ZI).
*> \endverbatim
*>
*> \param[in] D
*> \verbatim
*>          D is REAL
*>          The denominator part of a complex eigenvalue
*>          (ZR/D) + i*(ZI/D).
*> \endverbatim
*
*  Authors:
*  ========
*
*> \author Univ. of Tennessee
*> \author Univ. of California Berkeley
*> \author Univ. of Colorado Denver
*> \author NAG Ltd.
*
*> \ingroup single_eig
*
*  =====================================================================
      LOGICAL          FUNCTION slctes( ZR, ZI, D )
*
*  -- LAPACK test routine --
*  -- LAPACK is a software package provided by Univ. of Tennessee,    --
*  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
*
*     .. Scalar Arguments ..
      REAL               d, zi, zr
*     ..
*
*  =====================================================================
*
*     .. Parameters ..
      REAL               zero, one
      parameter( zero = 0.0e+0, one = 1.0e+0 )
*     ..
*     .. Intrinsic Functions ..
      INTRINSIC          sign
*     ..
*     .. Executable Statements ..
*
      IF( d.EQ.zero ) THEN
         slctes = ( zr.LT.zero )
      ELSE
         slctes = ( sign( one, zr ).NE.sign( one, d ) )
      END IF
*
      RETURN
*
*     End of SLCTES
*
      END