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    1: *> \brief \b DLAISNAN tests input for NaN by comparing two arguments for inequality.
    2: *
    3: *  =========== DOCUMENTATION ===========
    4: *
    5: * Online html documentation available at
    6: *            http://www.netlib.org/lapack/explore-html/
    7: *
    8: *> \htmlonly
    9: *> Download DLAISNAN + dependencies
   10: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dlaisnan.f">
   11: *> [TGZ]</a>
   12: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/dlaisnan.f">
   13: *> [ZIP]</a>
   14: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dlaisnan.f">
   15: *> [TXT]</a>
   16: *> \endhtmlonly
   17: *
   18: *  Definition:
   19: *  ===========
   20: *
   21: *       LOGICAL FUNCTION DLAISNAN( DIN1, DIN2 )
   22: *
   23: *       .. Scalar Arguments ..
   24: *       DOUBLE PRECISION, INTENT(IN) :: DIN1, DIN2
   25: *       ..
   26: *
   27: *
   28: *> \par Purpose:
   29: *  =============
   30: *>
   31: *> \verbatim
   32: *>
   33: *> This routine is not for general use.  It exists solely to avoid
   34: *> over-optimization in DISNAN.
   35: *>
   36: *> DLAISNAN checks for NaNs by comparing its two arguments for
   37: *> inequality.  NaN is the only floating-point value where NaN != NaN
   38: *> returns .TRUE.  To check for NaNs, pass the same variable as both
   39: *> arguments.
   40: *>
   41: *> A compiler must assume that the two arguments are
   42: *> not the same variable, and the test will not be optimized away.
   43: *> Interprocedural or whole-program optimization may delete this
   44: *> test.  The ISNAN functions will be replaced by the correct
   45: *> Fortran 03 intrinsic once the intrinsic is widely available.
   46: *> \endverbatim
   47: *
   48: *  Arguments:
   49: *  ==========
   50: *
   51: *> \param[in] DIN1
   52: *> \verbatim
   53: *>          DIN1 is DOUBLE PRECISION
   54: *> \endverbatim
   55: *>
   56: *> \param[in] DIN2
   57: *> \verbatim
   58: *>          DIN2 is DOUBLE PRECISION
   59: *>          Two numbers to compare for inequality.
   60: *> \endverbatim
   61: *
   62: *  Authors:
   63: *  ========
   64: *
   65: *> \author Univ. of Tennessee
   66: *> \author Univ. of California Berkeley
   67: *> \author Univ. of Colorado Denver
   68: *> \author NAG Ltd.
   69: *
   70: *> \ingroup OTHERauxiliary
   71: *
   72: *  =====================================================================
   73:       LOGICAL FUNCTION DLAISNAN( DIN1, DIN2 )
   74: *
   75: *  -- LAPACK auxiliary routine --
   76: *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
   77: *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
   78: *
   79: *     .. Scalar Arguments ..
   80:       DOUBLE PRECISION, INTENT(IN) :: DIN1, DIN2
   81: *     ..
   82: *
   83: *  =====================================================================
   84: *
   85: *  .. Executable Statements ..
   86:       DLAISNAN = (DIN1.NE.DIN2)
   87:       RETURN
   88:       END