Added thirdparty: boost library

thirdparty/include/boost/math/ccmath/sqrt.hpp

@@ -0,0 +1,80 @@
+//  (C) Copyright Matt Borland 2021.
+//  Use, modification and distribution are subject to the
+//  Boost Software License, Version 1.0. (See accompanying file
+//  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+//  Constexpr implementation of sqrt function
+
+#ifndef BOOST_MATH_CCMATH_SQRT
+#define BOOST_MATH_CCMATH_SQRT
+
+#include <boost/math/ccmath/detail/config.hpp>
+
+#ifdef BOOST_MATH_NO_CCMATH
+#error "The header <boost/math/sqrt.hpp> can only be used in C++17 and later."
+#endif
+
+#include <boost/math/ccmath/abs.hpp>
+#include <boost/math/ccmath/isnan.hpp>
+#include <boost/math/ccmath/isinf.hpp>
+#include <boost/math/tools/is_constant_evaluated.hpp>
+
+namespace boost::math::ccmath { 
+
+namespace detail {
+
+template <typename Real>
+constexpr Real sqrt_impl_2(Real x, Real s, Real s2)
+{
+    return !(s < s2) ? s2 : sqrt_impl_2(x, (x / s + s) / 2, s);
+}
+
+template <typename Real>
+constexpr Real sqrt_impl_1(Real x, Real s)
+{
+    return sqrt_impl_2(x, (x / s + s) / 2, s);
+}
+
+template <typename Real>
+constexpr Real sqrt_impl(Real x)
+{
+    return sqrt_impl_1(x, x > 1 ? x : Real(1));
+}
+
+} // namespace detail
+
+template <typename Real, std::enable_if_t<!std::is_integral_v<Real>, bool> = true>
+constexpr Real sqrt(Real x)
+{
+    if(BOOST_MATH_IS_CONSTANT_EVALUATED(x))
+    {
+        if (boost::math::ccmath::isnan(x) || 
+           (boost::math::ccmath::isinf(x) && x > 0) ||
+            boost::math::ccmath::abs(x) == Real(0))
+        {
+            return x;
+        }
+        // Domain error is implementation defined so return NAN
+        else if (boost::math::ccmath::isinf(x) && x < 0)
+        {
+            return std::numeric_limits<Real>::quiet_NaN();
+        }
+
+        return detail::sqrt_impl<Real>(x);
+    }
+    else
+    {
+        using std::sqrt;
+        return sqrt(x);
+    }
+}
+
+template <typename Z, std::enable_if_t<std::is_integral_v<Z>, bool> = true>
+constexpr double sqrt(Z x)
+{
+    return detail::sqrt_impl<double>(static_cast<double>(x));
+}
+
+} // Namespaces
+
+#endif // BOOST_MATH_CCMATH_SQRT