sladiv.f revision 7faaa9f3f0df9d23790277834d426c3d992ac3ba 
1*> \brief \b SLADIV
2*
3*  =========== DOCUMENTATION ===========
4*
5* Online html documentation available at
6*            http://www.netlib.org/lapack/explore-html/
7*
8*> \htmlonly
9*> Download SLADIV + dependencies
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11*> [TGZ]</a>
12*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/sladiv.f">
13*> [ZIP]</a>
14*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/sladiv.f">
15*> [TXT]</a>
16*> \endhtmlonly
17*
18*  Definition:
19*  ===========
20*
21*       SUBROUTINE SLADIV( A, B, C, D, P, Q )
22*
23*       .. Scalar Arguments ..
24*       REAL               A, B, C, D, P, Q
25*       ..
26*
27*
28*> \par Purpose:
29*  =============
30*>
31*> \verbatim
32*>
33*> SLADIV performs complex division in  real arithmetic
34*>
35*>                       a + i*b
36*>            p + i*q = ---------
37*>                       c + i*d
38*>
39*> The algorithm is due to Robert L. Smith and can be found
40*> in D. Knuth, The art of Computer Programming, Vol.2, p.195
41*> \endverbatim
42*
43*  Arguments:
44*  ==========
45*
46*> \param[in] A
47*> \verbatim
48*>          A is REAL
49*> \endverbatim
50*>
51*> \param[in] B
52*> \verbatim
53*>          B is REAL
54*> \endverbatim
55*>
56*> \param[in] C
57*> \verbatim
58*>          C is REAL
59*> \endverbatim
60*>
61*> \param[in] D
62*> \verbatim
63*>          D is REAL
64*>          The scalars a, b, c, and d in the above expression.
65*> \endverbatim
66*>
67*> \param[out] P
68*> \verbatim
69*>          P is REAL
70*> \endverbatim
71*>
72*> \param[out] Q
73*> \verbatim
74*>          Q is REAL
75*>          The scalars p and q in the above expression.
76*> \endverbatim
77*
78*  Authors:
79*  ========
80*
81*> \author Univ. of Tennessee
82*> \author Univ. of California Berkeley
83*> \author Univ. of Colorado Denver
84*> \author NAG Ltd.
85*
86*> \date November 2011
87*
88*> \ingroup auxOTHERauxiliary
89*
90*  =====================================================================
91      SUBROUTINE SLADIV( A, B, C, D, P, Q )
92*
93*  -- LAPACK auxiliary routine (version 3.4.0) --
94*  -- LAPACK is a software package provided by Univ. of Tennessee,    --
95*  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
96*     November 2011
97*
98*     .. Scalar Arguments ..
99      REAL               A, B, C, D, P, Q
100*     ..
101*
102*  =====================================================================
103*
104*     .. Local Scalars ..
105      REAL               E, F
106*     ..
107*     .. Intrinsic Functions ..
108      INTRINSIC          ABS
109*     ..
110*     .. Executable Statements ..
111*
112      IF( ABS( D ).LT.ABS( C ) ) THEN
113         E = D / C
114         F = C + D*E
115         P = ( A+B*E ) / F
116         Q = ( B-A*E ) / F
117      ELSE
118         E = C / D
119         F = D + C*E
120         P = ( B+A*E ) / F
121         Q = ( -A+B*E ) / F
122      END IF
123*
124      RETURN
125*
126*     End of SLADIV
127*
128      END
129