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/**
* \file Math.hpp
* \brief Header for GeographicLib::Math class
*
* Copyright (c) Charles Karney (2008-2019) <charles@karney.com> and licensed
* under the MIT/X11 License. For more information, see
* https://geographiclib.sourceforge.io/
**********************************************************************/
// Constants.hpp includes Math.hpp. Place this include outside Math.hpp's
// include guard to enforce this ordering.
#include "Constants.hpp"
#if !defined(GEOGRAPHICLIB_MATH_HPP)
#define GEOGRAPHICLIB_MATH_HPP 1
/**
* Are C++11 math functions available?
**********************************************************************/
#if !defined(GEOGRAPHICLIB_CXX11_MATH)
// Recent versions of g++ -std=c++11 (4.7 and later?) set __cplusplus to 201103
// and support the new C++11 mathematical functions, std::atanh, etc. However
// the Android toolchain, which uses g++ -std=c++11 (4.8 as of 2014-03-11,
// according to Pullan Lu), does not support std::atanh. Android toolchains
// might define __ANDROID__ or ANDROID; so need to check both. With OSX the
// version is GNUC version 4.2 and __cplusplus is set to 201103, so remove the
// version check on GNUC.
# if defined(__GNUC__) && __cplusplus >= 201103 && \
!(defined(__ANDROID__) || defined(ANDROID) || defined(__CYGWIN__))
# define GEOGRAPHICLIB_CXX11_MATH 1
// Visual C++ 12 supports these functions
# elif defined(_MSC_VER) && _MSC_VER >= 1800
# define GEOGRAPHICLIB_CXX11_MATH 1
# else
# define GEOGRAPHICLIB_CXX11_MATH 0
# endif
#endif
#if !defined(GEOGRAPHICLIB_WORDS_BIGENDIAN)
# define GEOGRAPHICLIB_WORDS_BIGENDIAN 0
#endif
#if !defined(GEOGRAPHICLIB_HAVE_LONG_DOUBLE)
# define GEOGRAPHICLIB_HAVE_LONG_DOUBLE 0
#endif
#if !defined(GEOGRAPHICLIB_PRECISION)
/**
* The precision of floating point numbers used in %GeographicLib. 1 means
* float (single precision); 2 (the default) means double; 3 means long double;
* 4 is reserved for quadruple precision. Nearly all the testing has been
* carried out with doubles and that's the recommended configuration. In order
* for long double to be used, GEOGRAPHICLIB_HAVE_LONG_DOUBLE needs to be
* defined. Note that with Microsoft Visual Studio, long double is the same as
* double.
**********************************************************************/
# define GEOGRAPHICLIB_PRECISION 2
#endif
#include <cmath>
#include <algorithm>
#include <limits>
#if GEOGRAPHICLIB_PRECISION == 4
#include <boost/version.hpp>
#include <boost/multiprecision/float128.hpp>
#include <boost/math/special_functions.hpp>
#elif GEOGRAPHICLIB_PRECISION == 5
#include <mpreal.h>
#endif
#if GEOGRAPHICLIB_PRECISION > 3
// volatile keyword makes no sense for multiprec types
#define GEOGRAPHICLIB_VOLATILE
// Signal a convergence failure with multiprec types by throwing an exception
// at loop exit.
#define GEOGRAPHICLIB_PANIC \
(throw GeographicLib::GeographicErr("Convergence failure"), false)
#else
#define GEOGRAPHICLIB_VOLATILE volatile
// Ignore convergence failures with standard floating points types by allowing
// loop to exit cleanly.
#define GEOGRAPHICLIB_PANIC false
#endif
namespace GeographicLib {
/**
* \brief Mathematical functions needed by %GeographicLib
*
* Define mathematical functions in order to localize system dependencies and
* to provide generic versions of the functions. In addition define a real
* type to be used by %GeographicLib.
*
* Example of use:
* \include example-Math.cpp
**********************************************************************/
class Math {
private:
void dummy(); // Static check for GEOGRAPHICLIB_PRECISION
Math(); // Disable constructor
public:
#if GEOGRAPHICLIB_HAVE_LONG_DOUBLE
/**
* The extended precision type for real numbers, used for some testing.
* This is long double on computers with this type; otherwise it is double.
**********************************************************************/
typedef long double extended;
#else
typedef double extended;
#endif
#if GEOGRAPHICLIB_PRECISION == 2
/**
* The real type for %GeographicLib. Nearly all the testing has been done
* with \e real = double. However, the algorithms should also work with
* float and long double (where available). (<b>CAUTION</b>: reasonable
* accuracy typically cannot be obtained using floats.)
**********************************************************************/
typedef double real;
#elif GEOGRAPHICLIB_PRECISION == 1
typedef float real;
#elif GEOGRAPHICLIB_PRECISION == 3
typedef extended real;
#elif GEOGRAPHICLIB_PRECISION == 4
typedef boost::multiprecision::float128 real;
#elif GEOGRAPHICLIB_PRECISION == 5
typedef mpfr::mpreal real;
#else
typedef double real;
#endif
/**
* @return the number of bits of precision in a real number.
**********************************************************************/
static int digits();
/**
* Set the binary precision of a real number.
*
* @param[in] ndigits the number of bits of precision.
* @return the resulting number of bits of precision.
*
* This only has an effect when GEOGRAPHICLIB_PRECISION = 5. See also
* Utility::set_digits for caveats about when this routine should be
* called.
**********************************************************************/
static int set_digits(int ndigits);
/**
* @return the number of decimal digits of precision in a real number.
**********************************************************************/
static int digits10();
/**
* Number of additional decimal digits of precision for real relative to
* double (0 for float).
**********************************************************************/
static int extra_digits();
/**
* true if the machine is big-endian.
**********************************************************************/
static const bool bigendian = GEOGRAPHICLIB_WORDS_BIGENDIAN;
/**
* @tparam T the type of the returned value.
* @return π.
**********************************************************************/
template<typename T> static T pi() {
using std::atan2;
static const T pi = atan2(T(0), T(-1));
return pi;
}
/**
* A synonym for pi<real>().
**********************************************************************/
static real pi() { return pi<real>(); }
/**
* @tparam T the type of the returned value.
* @return the number of radians in a degree.
**********************************************************************/
template<typename T> static T degree() {
static const T degree = pi<T>() / 180;
return degree;
}
/**
* A synonym for degree<real>().
**********************************************************************/
static real degree() { return degree<real>(); }
/**
* Square a number.
*
* @tparam T the type of the argument and the returned value.
* @param[in] x
* @return <i>x</i><sup>2</sup>.
**********************************************************************/
template<typename T> static T sq(T x)
{ return x * x; }
/**
* The hypotenuse function avoiding underflow and overflow.
*
* @tparam T the type of the arguments and the returned value.
* @param[in] x
* @param[in] y
* @return sqrt(<i>x</i><sup>2</sup> + <i>y</i><sup>2</sup>).
**********************************************************************/
template<typename T> static T hypot(T x, T y);
/**
* exp(\e x) − 1 accurate near \e x = 0.
*
* @tparam T the type of the argument and the returned value.
* @param[in] x
* @return exp(\e x) − 1.
**********************************************************************/
template<typename T> static T expm1(T x);
/**
* log(1 + \e x) accurate near \e x = 0.
*
* @tparam T the type of the argument and the returned value.
* @param[in] x
* @return log(1 + \e x).
**********************************************************************/
template<typename T> static T log1p(T x);
/**
* The inverse hyperbolic sine function.
*
* @tparam T the type of the argument and the returned value.
* @param[in] x
* @return asinh(\e x).
**********************************************************************/
template<typename T> static T asinh(T x);
/**
* The inverse hyperbolic tangent function.
*
* @tparam T the type of the argument and the returned value.
* @param[in] x
* @return atanh(\e x).
**********************************************************************/
template<typename T> static T atanh(T x);
/**
* Copy the sign.
*
* @tparam T the type of the argument.
* @param[in] x gives the magitude of the result.
* @param[in] y gives the sign of the result.
* @return value with the magnitude of \e x and with the sign of \e y.
*
* This routine correctly handles the case \e y = −0, returning
* &minus|<i>x</i>|.
**********************************************************************/
template<typename T> static T copysign(T x, T y);
/**
* The cube root function.
*
* @tparam T the type of the argument and the returned value.
* @param[in] x
* @return the real cube root of \e x.
**********************************************************************/
template<typename T> static T cbrt(T x);
/**
* The remainder function.
*
* @tparam T the type of the arguments and the returned value.
* @param[in] x
* @param[in] y
* @return the remainder of \e x/\e y in the range [−\e y/2, \e y/2].
**********************************************************************/
template<typename T> static T remainder(T x, T y);
/**
* The remquo function.
*
* @tparam T the type of the arguments and the returned value.
* @param[in] x
* @param[in] y
* @param[out] n the low 3 bits of the quotient
* @return the remainder of \e x/\e y in the range [−\e y/2, \e y/2].
**********************************************************************/
template<typename T> static T remquo(T x, T y, int* n);
/**
* The round function.
*
* @tparam T the type of the argument and the returned value.
* @param[in] x
* @return \e x round to the nearest integer (ties round away from 0).
**********************************************************************/
template<typename T> static T round(T x);
/**
* The lround function.
*
* @tparam T the type of the argument.
* @param[in] x
* @return \e x round to the nearest integer as a long int (ties round away
* from 0).
*
* If the result does not fit in a long int, the return value is undefined.
**********************************************************************/
template<typename T> static long lround(T x);
/**
* Fused multiply and add.
*
* @tparam T the type of the arguments and the returned value.
* @param[in] x
* @param[in] y
* @param[in] z
* @return <i>xy</i> + <i>z</i>, correctly rounded (on those platforms with
* support for the <code>fma</code> instruction).
*
* On platforms without the <code>fma</code> instruction, no attempt is
* made to improve on the result of a rounded multiplication followed by a
* rounded addition.
**********************************************************************/
template<typename T> static T fma(T x, T y, T z);
/**
* Normalize a two-vector.
*
* @tparam T the type of the argument and the returned value.
* @param[in,out] x on output set to <i>x</i>/hypot(<i>x</i>, <i>y</i>).
* @param[in,out] y on output set to <i>y</i>/hypot(<i>x</i>, <i>y</i>).
**********************************************************************/
template<typename T> static void norm(T& x, T& y)
{ T h = hypot(x, y); x /= h; y /= h; }
/**
* The error-free sum of two numbers.
*
* @tparam T the type of the argument and the returned value.
* @param[in] u
* @param[in] v
* @param[out] t the exact error given by (\e u + \e v) - \e s.
* @return \e s = round(\e u + \e v).
*
* See D. E. Knuth, TAOCP, Vol 2, 4.2.2, Theorem B. (Note that \e t can be
* the same as one of the first two arguments.)
**********************************************************************/
template<typename T> static T sum(T u, T v, T& t);
/**
* Evaluate a polynomial.
*
* @tparam T the type of the arguments and returned value.
* @param[in] N the order of the polynomial.
* @param[in] p the coefficient array (of size \e N + 1).
* @param[in] x the variable.
* @return the value of the polynomial.
*
* Evaluate <i>y</i> = ∑<sub><i>n</i>=0..<i>N</i></sub>
* <i>p</i><sub><i>n</i></sub> <i>x</i><sup><i>N</i>−<i>n</i></sup>.
* Return 0 if \e N < 0. Return <i>p</i><sub>0</sub>, if \e N = 0 (even
* if \e x is infinite or a nan). The evaluation uses Horner's method.
**********************************************************************/
template<typename T> static T polyval(int N, const T p[], T x)
// This used to employ Math::fma; but that's too slow and it seemed not to
// improve the accuracy noticeably. This might change when there's direct
// hardware support for fma.
{ T y = N < 0 ? 0 : *p++; while (--N >= 0) y = y * x + *p++; return y; }
/**
* Normalize an angle.
*
* @tparam T the type of the argument and returned value.
* @param[in] x the angle in degrees.
* @return the angle reduced to the range (−180°, 180°].
*
* The range of \e x is unrestricted.
**********************************************************************/
template<typename T> static T AngNormalize(T x) {
x = remainder(x, T(360)); return x != -180 ? x : 180;
}
/**
* Normalize a latitude.
*
* @tparam T the type of the argument and returned value.
* @param[in] x the angle in degrees.
* @return x if it is in the range [−90°, 90°], otherwise
* return NaN.
**********************************************************************/
template<typename T> static T LatFix(T x)
{ using std::abs; return abs(x) > 90 ? NaN<T>() : x; }
/**
* The exact difference of two angles reduced to
* (−180°, 180°].
*
* @tparam T the type of the arguments and returned value.
* @param[in] x the first angle in degrees.
* @param[in] y the second angle in degrees.
* @param[out] e the error term in degrees.
* @return \e d, the truncated value of \e y − \e x.
*
* This computes \e z = \e y − \e x exactly, reduced to
* (−180°, 180°]; and then sets \e z = \e d + \e e where \e d
* is the nearest representable number to \e z and \e e is the truncation
* error. If \e d = −180, then \e e > 0; If \e d = 180, then \e e
* ≤ 0.
**********************************************************************/
template<typename T> static T AngDiff(T x, T y, T& e) {
T t, d = AngNormalize(sum(remainder(-x, T(360)),
remainder( y, T(360)), t));
// Here y - x = d + t (mod 360), exactly, where d is in (-180,180] and
// abs(t) <= eps (eps = 2^-45 for doubles). The only case where the
// addition of t takes the result outside the range (-180,180] is d = 180
// and t > 0. The case, d = -180 + eps, t = -eps, can't happen, since
// sum would have returned the exact result in such a case (i.e., given t
// = 0).
return sum(d == 180 && t > 0 ? -180 : d, t, e);
}
/**
* Difference of two angles reduced to [−180°, 180°]
*
* @tparam T the type of the arguments and returned value.
* @param[in] x the first angle in degrees.
* @param[in] y the second angle in degrees.
* @return \e y − \e x, reduced to the range [−180°,
* 180°].
*
* The result is equivalent to computing the difference exactly, reducing
* it to (−180°, 180°] and rounding the result. Note that
* this prescription allows −180° to be returned (e.g., if \e x
* is tiny and negative and \e y = 180°).
**********************************************************************/
template<typename T> static T AngDiff(T x, T y)
{ T e; return AngDiff(x, y, e); }
/**
* Coarsen a value close to zero.
*
* @tparam T the type of the argument and returned value.
* @param[in] x
* @return the coarsened value.
*
* The makes the smallest gap in \e x = 1/16 − nextafter(1/16, 0) =
* 1/2<sup>57</sup> for reals = 0.7 pm on the earth if \e x is an angle in
* degrees. (This is about 1000 times more resolution than we get with
* angles around 90°.) We use this to avoid having to deal with near
* singular cases when \e x is non-zero but tiny (e.g.,
* 10<sup>−200</sup>). This converts −0 to +0; however tiny
* negative numbers get converted to −0.
**********************************************************************/
template<typename T> static T AngRound(T x);
/**
* Evaluate the sine and cosine function with the argument in degrees
*
* @tparam T the type of the arguments.
* @param[in] x in degrees.
* @param[out] sinx sin(<i>x</i>).
* @param[out] cosx cos(<i>x</i>).
*
* The results obey exactly the elementary properties of the trigonometric
* functions, e.g., sin 9° = cos 81° = − sin 123456789°.
* If x = −0, then \e sinx = −0; this is the only case where
* −0 is returned.
**********************************************************************/
template<typename T> static void sincosd(T x, T& sinx, T& cosx);
/**
* Evaluate the sine function with the argument in degrees
*
* @tparam T the type of the argument and the returned value.
* @param[in] x in degrees.
* @return sin(<i>x</i>).
**********************************************************************/
template<typename T> static T sind(T x);
/**
* Evaluate the cosine function with the argument in degrees
*
* @tparam T the type of the argument and the returned value.
* @param[in] x in degrees.
* @return cos(<i>x</i>).
**********************************************************************/
template<typename T> static T cosd(T x);
/**
* Evaluate the tangent function with the argument in degrees
*
* @tparam T the type of the argument and the returned value.
* @param[in] x in degrees.
* @return tan(<i>x</i>).
*
* If \e x = ±90°, then a suitably large (but finite) value is
* returned.
**********************************************************************/
template<typename T> static T tand(T x);
/**
* Evaluate the atan2 function with the result in degrees
*
* @tparam T the type of the arguments and the returned value.
* @param[in] y
* @param[in] x
* @return atan2(<i>y</i>, <i>x</i>) in degrees.
*
* The result is in the range (−180° 180°]. N.B.,
* atan2d(±0, −1) = +180°; atan2d(−ε,
* −1) = −180°, for ε positive and tiny;
* atan2d(±0, +1) = ±0°.
**********************************************************************/
template<typename T> static T atan2d(T y, T x);
/**
* Evaluate the atan function with the result in degrees
*
* @tparam T the type of the argument and the returned value.
* @param[in] x
* @return atan(<i>x</i>) in degrees.
**********************************************************************/
template<typename T> static T atand(T x);
/**
* Evaluate <i>e</i> atanh(<i>e x</i>)
*
* @tparam T the type of the argument and the returned value.
* @param[in] x
* @param[in] es the signed eccentricity = sign(<i>e</i><sup>2</sup>)
* sqrt(|<i>e</i><sup>2</sup>|)
* @return <i>e</i> atanh(<i>e x</i>)
*
* If <i>e</i><sup>2</sup> is negative (<i>e</i> is imaginary), the
* expression is evaluated in terms of atan.
**********************************************************************/
template<typename T> static T eatanhe(T x, T es);
/**
* tanχ in terms of tanφ
*
* @tparam T the type of the argument and the returned value.
* @param[in] tau τ = tanφ
* @param[in] es the signed eccentricity = sign(<i>e</i><sup>2</sup>)
* sqrt(|<i>e</i><sup>2</sup>|)
* @return τ′ = tanχ
*
* See Eqs. (7--9) of
* C. F. F. Karney,
* <a href="https://doi.org/10.1007/s00190-011-0445-3">
* Transverse Mercator with an accuracy of a few nanometers,</a>
* J. Geodesy 85(8), 475--485 (Aug. 2011)
* (preprint
* <a href="https://arxiv.org/abs/1002.1417">arXiv:1002.1417</a>).
**********************************************************************/
template<typename T> static T taupf(T tau, T es);
/**
* tanφ in terms of tanχ
*
* @tparam T the type of the argument and the returned value.
* @param[in] taup τ′ = tanχ
* @param[in] es the signed eccentricity = sign(<i>e</i><sup>2</sup>)
* sqrt(|<i>e</i><sup>2</sup>|)
* @return τ = tanφ
*
* See Eqs. (19--21) of
* C. F. F. Karney,
* <a href="https://doi.org/10.1007/s00190-011-0445-3">
* Transverse Mercator with an accuracy of a few nanometers,</a>
* J. Geodesy 85(8), 475--485 (Aug. 2011)
* (preprint
* <a href="https://arxiv.org/abs/1002.1417">arXiv:1002.1417</a>).
**********************************************************************/
template<typename T> static T tauf(T taup, T es);
/**
* Test for finiteness.
*
* @tparam T the type of the argument.
* @param[in] x
* @return true if number is finite, false if NaN or infinite.
**********************************************************************/
template<typename T> static bool isfinite(T x);
/**
* The NaN (not a number)
*
* @tparam T the type of the returned value.
* @return NaN if available, otherwise return the max real of type T.
**********************************************************************/
template<typename T> static T NaN();
/**
* A synonym for NaN<real>().
**********************************************************************/
static real NaN() { return NaN<real>(); }
/**
* Test for NaN.
*
* @tparam T the type of the argument.
* @param[in] x
* @return true if argument is a NaN.
**********************************************************************/
template<typename T> static bool isnan(T x);
/**
* Infinity
*
* @tparam T the type of the returned value.
* @return infinity if available, otherwise return the max real.
**********************************************************************/
template<typename T> static T infinity();
/**
* A synonym for infinity<real>().
**********************************************************************/
static real infinity() { return infinity<real>(); }
/**
* Swap the bytes of a quantity
*
* @tparam T the type of the argument and the returned value.
* @param[in] x
* @return x with its bytes swapped.
**********************************************************************/
template<typename T> static T swab(T x) {
union {
T r;
unsigned char c[sizeof(T)];
} b;
b.r = x;
for (int i = sizeof(T)/2; i--; )
std::swap(b.c[i], b.c[sizeof(T) - 1 - i]);
return b.r;
}
};
} // namespace GeographicLib
#endif // GEOGRAPHICLIB_MATH_HPP