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*> \brief \b SLAPY2 returns sqrt(x2+y2).
*
* =========== DOCUMENTATION ===========
*
* Online html documentation available at
* http://www.netlib.org/lapack/explore-html/
*
*> \htmlonly
*> Download SLAPY2 + dependencies
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/slapy2.f">
*> [TGZ]</a>
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/slapy2.f">
*> [ZIP]</a>
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/slapy2.f">
*> [TXT]</a>
*> \endhtmlonly
*
* Definition:
* ===========
*
* REAL FUNCTION SLAPY2( X, Y )
*
* .. Scalar Arguments ..
* REAL X, Y
* ..
*
*
*> \par Purpose:
* =============
*>
*> \verbatim
*>
*> SLAPY2 returns sqrt(x**2+y**2), taking care not to cause unnecessary
*> overflow and unnecessary underflow.
*> \endverbatim
*
* Arguments:
* ==========
*
*> \param[in] X
*> \verbatim
*> X is REAL
*> \endverbatim
*>
*> \param[in] Y
*> \verbatim
*> Y is REAL
*> X and Y specify the values x and y.
*> \endverbatim
*
* Authors:
* ========
*
*> \author Univ. of Tennessee
*> \author Univ. of California Berkeley
*> \author Univ. of Colorado Denver
*> \author NAG Ltd.
*
*> \ingroup OTHERauxiliary
*
* =====================================================================
REAL FUNCTION SLAPY2( X, Y )
*
* -- LAPACK auxiliary routine --
* -- LAPACK is a software package provided by Univ. of Tennessee, --
* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
*
* .. Scalar Arguments ..
REAL X, Y
* ..
*
* =====================================================================
*
* .. Parameters ..
REAL ZERO
PARAMETER ( ZERO = 0.0E0 )
REAL ONE
PARAMETER ( ONE = 1.0E0 )
* ..
* .. Local Scalars ..
REAL W, XABS, YABS, Z, HUGEVAL
LOGICAL X_IS_NAN, Y_IS_NAN
* ..
* .. External Functions ..
LOGICAL SISNAN
EXTERNAL SISNAN
* ..
* .. External Subroutines ..
REAL SLAMCH
* ..
* .. Intrinsic Functions ..
INTRINSIC ABS, MAX, MIN, SQRT
* ..
* .. Executable Statements ..
*
X_IS_NAN = SISNAN( X )
Y_IS_NAN = SISNAN( Y )
IF ( X_IS_NAN ) SLAPY2 = X
IF ( Y_IS_NAN ) SLAPY2 = Y
HUGEVAL = SLAMCH( 'Overflow' )
*
IF ( .NOT.( X_IS_NAN.OR.Y_IS_NAN ) ) THEN
XABS = ABS( X )
YABS = ABS( Y )
W = MAX( XABS, YABS )
Z = MIN( XABS, YABS )
IF( Z.EQ.ZERO .OR. W.GT.HUGEVAL ) THEN
SLAPY2 = W
ELSE
SLAPY2 = W*SQRT( ONE+( Z / W )**2 )
END IF
END IF
RETURN
*
* End of SLAPY2
*
END
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