nan.hpp

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# ifndef CPPAD_UTILITY_NAN_HPP
# define CPPAD_UTILITY_NAN_HPP

/* --------------------------------------------------------------------------
CppAD: C++ Algorithmic Differentiation: Copyright (C) 2003-17 Bradley M. Bell

CppAD is distributed under multiple licenses. This distribution is under
the terms of the
                    Eclipse Public License Version 1.0.

A copy of this license is included in the COPYING file of this distribution.
Please visit http://www.coin-or.org/CppAD/ for information on other licenses.
-------------------------------------------------------------------------- */
/*
$begin nan$$
$spell
     hasnan
     cppad
     hpp
     CppAD
     isnan
     bool
     const
$$

$section Obtain Nan or Determine if a Value is Nan$$

$head Syntax$$
$codei%# include <cppad/utility/nan.hpp>
%$$
$icode%b% = isnan(%s%)
%$$
$icode%b% = hasnan(%v%)%$$

$head Purpose$$
It obtain and check for the value not a number $code nan$$.
The IEEE standard specifies that a floating point value $icode a$$
is $code nan$$ if and only if the following returns true
$codei%
     %a% != %a%
%$$

$head Include$$
The file $code cppad/nan.hpp$$ is included by $code cppad/cppad.hpp$$
but it can also be included separately with out the rest of
the $code CppAD$$ routines.

$subhead Macros$$
Some C++ compilers use preprocessor symbols called $code nan$$
and $code isnan$$.
These preprocessor symbols will no longer be defined after
this file is included.

$head isnan$$
This routine determines if a scalar value is $code nan$$.

$subhead s$$
The argument $icode s$$ has prototype
$codei%
     const %Scalar% %s%
%$$

$subhead b$$
The return value $icode b$$ has prototype
$codei%
     bool %b%
%$$
It is true if the value $icode s$$ is $code nan$$.

$head hasnan$$
This routine determines if a
$cref SimpleVector$$ has an element that is $code nan$$.

$subhead v$$
The argument $icode v$$ has prototype
$codei%
     const %Vector% &%v%
%$$
(see $cref/Vector/nan/Vector/$$ for the definition of $icode Vector$$).

$subhead b$$
The return value $icode b$$ has prototype
$codei%
     bool %b%
%$$
It is true if the vector $icode v$$ has a $code nan$$.


$head nan(zero)$$

$subhead Deprecated 2015-10-04$$
This routine has been deprecated, use CppAD numeric limits
$cref/quiet_NaN/numeric_limits/quiet_NaN/$$ in its place.

$subhead Syntax$$
$icode%s% = nan(%z%)
%$$

$subhead z$$
The argument $icode z$$ has prototype
$codei%
     const %Scalar% &%z%
%$$
and its value is zero
(see $cref/Scalar/nan/Scalar/$$ for the definition of $icode Scalar$$).

$subhead s$$
The return value $icode s$$ has prototype
$codei%
     %Scalar% %s%
%$$
It is the value $code nan$$ for this floating point type.

$head Scalar$$
The type $icode Scalar$$ must support the following operations;
$table
$bold Operation$$ $cnext $bold Description$$  $rnext
$icode%a% / %b%$$ $cnext
     division operator (returns a $icode Scalar$$ object)
$rnext
$icode%a% == %b%$$ $cnext
     equality operator (returns a $code bool$$ object)
$rnext
$icode%a% != %b%$$ $cnext
     not equality operator (returns a $code bool$$ object)
$tend
Note that the division operator will be used with $icode a$$ and $icode b$$
equal to zero. For some types (e.g. $code int$$) this may generate
an exception. No attempt is made to catch any such exception.

$head Vector$$
The type $icode Vector$$ must be a $cref SimpleVector$$ class with
elements of type $icode Scalar$$.

$children%
     example/utility/nan.cpp
%$$
$head Example$$
The file $cref nan.cpp$$
contains an example and test of this routine.
It returns true if it succeeds and false otherwise.

$end
*/

# include <cstddef>
# include <cppad/core/cppad_assert.hpp>

// needed before one can use CPPAD_ASSERT_FIRST_CALL_NOT_PARALLEL
# include <cppad/utility/thread_alloc.hpp>

/*
# define nan There must be a define for every CppAD undef
*/
# ifdef nan
# undef nan
# endif

/*
# define isnan There must be a define for every CppAD undef
*/
# ifdef isnan
# undef isnan
# endif

namespace CppAD { // BEGIN CppAD namespace

template <class Scalar>
inline bool isnan(const Scalar &s)
{    return (s != s);
}

template <class Vector>
bool hasnan(const Vector &v)
{
     bool found_nan;
     size_t i;
     i   = v.size();
     found_nan = false;
     // on MS Visual Studio 2012, CppAD required in front of isnan ?
     while(i--)
          found_nan |= CppAD::isnan(v[i]);
     return found_nan;
}

template <class Scalar>
inline Scalar nan(const Scalar &zero)
{    return zero / zero;
}

} // End CppAD namespace

# endif