SLARTGP generates a plane rotation so that


    [  CS  SN  ]  .  [ F ]  =  [ R ]   where CS**2 + SN**2 = 1.


    [ -SN  CS  ]     [ G ]     [ 0 ]


 This is a slower, more accurate version of the Level 1 BLAS routine SROTG,


 with the following other differences:


    F and G are unchanged on return.


    If G=0, then CS=(+/-)1 and SN=0.


    If F=0 and (G .ne. 0), then CS=0 and SN=(+/-)1.


 The sign is chosen so that R >= 0.

F

          F is REAL


          The first component of vector to be rotated.

G

          G is REAL


          The second component of vector to be rotated.

CS

          CS is REAL


          The cosine of the rotation.

SN

          SN is REAL


          The sine of the rotation.

R

          R is REAL


          The nonzero component of the rotated vector.


  This version has a few statements commented out for thread safety


  (machine parameters are computed on each entry). 10 feb 03, SJH.

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December 2016