1*> \brief \b DLAPY2 returns sqrt(x2+y2).
2*
3*  =========== DOCUMENTATION ===========
4*
5* Online html documentation available at
6*            http://www.netlib.org/lapack/explore-html/
7*
8*> \htmlonly
9*> Download DLAPY2 + dependencies
10*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dlapy2.f">
11*> [TGZ]</a>
12*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/dlapy2.f">
13*> [ZIP]</a>
14*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dlapy2.f">
15*> [TXT]</a>
16*> \endhtmlonly
17*
18*  Definition:
19*  ===========
20*
21*       DOUBLE PRECISION FUNCTION DLAPY2( X, Y )
22*
23*       .. Scalar Arguments ..
24*       DOUBLE PRECISION   X, Y
25*       ..
26*
27*
28*> \par Purpose:
29*  =============
30*>
31*> \verbatim
32*>
33*> DLAPY2 returns sqrt(x**2+y**2), taking care not to cause unnecessary
34*> overflow and unnecessary underflow.
35*> \endverbatim
36*
37*  Arguments:
38*  ==========
39*
40*> \param[in] X
41*> \verbatim
42*>          X is DOUBLE PRECISION
43*> \endverbatim
44*>
45*> \param[in] Y
46*> \verbatim
47*>          Y is DOUBLE PRECISION
48*>          X and Y specify the values x and y.
49*> \endverbatim
50*
51*  Authors:
52*  ========
53*
54*> \author Univ. of Tennessee
55*> \author Univ. of California Berkeley
56*> \author Univ. of Colorado Denver
57*> \author NAG Ltd.
58*
59*> \ingroup OTHERauxiliary
60*
61*  =====================================================================
62      DOUBLE PRECISION FUNCTION DLAPY2( X, Y )
63*
64*  -- LAPACK auxiliary routine --
65*  -- LAPACK is a software package provided by Univ. of Tennessee,    --
66*  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
67*
68*     .. Scalar Arguments ..
69      DOUBLE PRECISION   X, Y
70*     ..
71*
72*  =====================================================================
73*
74*     .. Parameters ..
75      DOUBLE PRECISION   ZERO
76      PARAMETER          ( ZERO = 0.0D0 )
77      DOUBLE PRECISION   ONE
78      PARAMETER          ( ONE = 1.0D0 )
79*     ..
80*     .. Local Scalars ..
81      DOUBLE PRECISION   W, XABS, YABS, Z
82      LOGICAL            X_IS_NAN, Y_IS_NAN
83*     ..
84*     .. External Functions ..
85      LOGICAL            DISNAN
86      EXTERNAL           DISNAN
87*     ..
88*     .. Intrinsic Functions ..
89      INTRINSIC          ABS, MAX, MIN, SQRT
90*     ..
91*     .. Executable Statements ..
92*
93      X_IS_NAN = DISNAN( X )
94      Y_IS_NAN = DISNAN( Y )
95      IF ( X_IS_NAN ) DLAPY2 = X
96      IF ( Y_IS_NAN ) DLAPY2 = Y
97*
98      IF ( .NOT.( X_IS_NAN.OR.Y_IS_NAN ) ) THEN
99         XABS = ABS( X )
100         YABS = ABS( Y )
101         W = MAX( XABS, YABS )
102         Z = MIN( XABS, YABS )
103         IF( Z.EQ.ZERO ) THEN
104            DLAPY2 = W
105         ELSE
106            DLAPY2 = W*SQRT( ONE+( Z / W )**2 )
107         END IF
108      END IF
109      RETURN
110*
111*     End of DLAPY2
112*
113      END
114