slartgs.f3

!>
!> SLARTGS generates a plane rotation designed to introduce a bulge in
!> Golub-Reinsch-style implicit QR iteration for the bidiagonal SVD
!> problem. X and Y are the top-row entries, and SIGMA is the shift.
!> The computed CS and SN define a plane rotation satisfying
!>
!>    [  CS  SN  ]  .  [ X^2 - SIGMA ]  =  [ R ],
!>    [ -SN  CS  ]     [    X * Y    ]     [ 0 ]
!>
!> with R nonnegative.  If X^2 - SIGMA and X * Y are 0, then the
!> rotation is by PI/2.
!> 

X

!>          X is REAL
!>          The (1,1) entry of an upper bidiagonal matrix.
!> 

Y

!>          Y is REAL
!>          The (1,2) entry of an upper bidiagonal matrix.
!> 

SIGMA

!>          SIGMA is REAL
!>          The shift.
!> 

CS

!>          CS is REAL
!>          The cosine of the rotation.
!> 

SN

!>          SN is REAL
!>          The sine of the rotation.
!> 

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