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NAME
     dlanv2 - compute the Schur factorization of  a  real  2-by-2
     nonsymmetric matrix in standard form

SYNOPSIS
     SUBROUTINE DLANV2( A, B, C, D, RT1R, RT1I, RT2R,  RT2I,  CS,
               SN )

     DOUBLE PRECISION A, B, C, CS, D, RT1I, RT1R, RT2I, RT2R, SN



     #include <sunperf.h>

     void dlanv2(double *da, double *db, double *dc,  double  *d,
               double  *rt1r,  double *rt1i, double *rt2r, double
               *rt2i, double *cs, double *sn) ;

PURPOSE
     DLANV2 computes the Schur factorization  of  a  real  2-by-2
     nonsymmetric matrix in standard form:

          [ A  B ] = [ CS -SN ] [ AA  BB ] [ CS  SN ]
          [ C  D ]   [ SN  CS ] [ CC  DD ] [-SN  CS ]

     where either
     1) CC = 0 so that AA and DD  are  real  eigenvalues  of  the
     matrix,  or  2)  AA  =  DD  and BB*CC < 0, so that AA + or -
     sqrt(BB*CC) are complex conjugate eigenvalues.


ARGUMENTS
     A         (input/output) DOUBLE PRECISION
               B         (input/output)   DOUBLE   PRECISION    C
               (input/output)       DOUBLE       PRECISION      D
               (input/output) DOUBLE PRECISION On entry, the ele-
               ments  of  the  input  matrix.   On exit, they are
               overwritten by the elements  of  the  standardised
               Schur form.

     RT1R      (output) DOUBLE PRECISION
               RT1I    (output) DOUBLE PRECISION RT2R    (output)
               DOUBLE PRECISION RT2I    (output) DOUBLE PRECISION
               The real and imaginary parts of  the  eigenvalues.
               If  the  eigenvalues  are  both real, abs(RT1R) >=
               abs(RT2R); if the eigenvalues are a complex conju-
               gate pair, RT1I > 0.

     CS        (output) DOUBLE PRECISION
               SN      (output) DOUBLE  PRECISION  Parameters  of
               the rotation matrix.

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