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Add 3-arg hypot #914

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Add 3-arg hypot #914

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824f03d
Add 3-arg hypot
mborland Jan 9, 2023
b298d71
Remove float128 testing
mborland Jan 10, 2023
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63 changes: 63 additions & 0 deletions include/boost/math/ccmath/hypot.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,7 @@
#include <boost/math/ccmath/abs.hpp>
#include <boost/math/ccmath/isinf.hpp>
#include <boost/math/ccmath/isnan.hpp>
#include <boost/math/ccmath/fmax.hpp>
#include <boost/math/ccmath/detail/swap.hpp>

namespace boost::math::ccmath {
Expand All @@ -44,6 +45,20 @@ constexpr T hypot_impl(T x, T y) noexcept
return x * boost::math::ccmath::sqrt(1 + rat * rat);
}

template <typename T>
constexpr T hypot_impl(T x, T y, T z) noexcept
{
x = boost::math::ccmath::abs(x);
y = boost::math::ccmath::abs(y);
z = boost::math::ccmath::abs(z);

T a = boost::math::ccmath::fmax(boost::math::ccmath::fmax(x, y), z);

return a * boost::math::ccmath::sqrt((x / a) * (x / a)
+ (y / a) * (y / a)
+ (z / a) * (z / a));
}

} // Namespace detail

template <typename Real, std::enable_if_t<!std::is_integral_v<Real>, bool> = true>
Expand Down Expand Up @@ -109,6 +124,54 @@ constexpr long double hypotl(long double x, long double y) noexcept
}
#endif

template <typename Real, std::enable_if_t<!std::is_integral_v<Real>, bool> = true>
constexpr auto hypot(Real x, Real y, Real z) noexcept
{
if (BOOST_MATH_IS_CONSTANT_EVALUATED(x))
{
if (boost::math::ccmath::isinf(x) || boost::math::ccmath::isinf(y) || boost::math::ccmath::isinf(z))
{
return std::numeric_limits<Real>::infinity();
}
else if (boost::math::ccmath::isnan(x))
{
return x;
}
else if (boost::math::ccmath::isnan(y))
{
return y;
}
else if (boost::math::ccmath::isnan(z))
{
return z;
}

return detail::hypot_impl(x, y, z);
}
else
{
using std::hypot;
return hypot(x, y, z);
}
}

template <typename T1, typename T2, typename T3>
constexpr auto hypot(T1 x, T2 y, T3 z) noexcept
{
if (BOOST_MATH_IS_CONSTANT_EVALUATED(x))
{
using promoted_type = tools::promote_args_t<T1, T2, T3>;
return boost::math::ccmath::hypot(static_cast<promoted_type>(x),
static_cast<promoted_type>(y),
static_cast<promoted_type>(z));
}
else
{
using std::hypot;
return hypot(x, y, z);
}
}

} // Namespaces

#endif // BOOST_MATH_CCMATH_HYPOT_HPP
47 changes: 47 additions & 0 deletions test/ccmath_hypot_test.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -54,6 +54,46 @@ constexpr void test()
static_assert(boost::math::ccmath::hypot(T(2), T(2)) == boost::math::ccmath::sqrt(T(8)));
}

template <typename T>
constexpr void test_3_arg()
{
constexpr T tol = 5 * std::numeric_limits<T>::epsilon();

// Error Handling
if constexpr (std::numeric_limits<T>::has_quiet_NaN)
{
static_assert(boost::math::ccmath::isnan(boost::math::ccmath::hypot(std::numeric_limits<T>::quiet_NaN(), T(1), T(1))), "If x is NaN, NaN is returned");
static_assert(boost::math::ccmath::isnan(boost::math::ccmath::hypot(T(1), std::numeric_limits<T>::quiet_NaN(), T(1))), "If y is NaN, NaN is returned");
static_assert(boost::math::ccmath::isnan(boost::math::ccmath::hypot(T(1), T(1), std::numeric_limits<T>::quiet_NaN())), "If z is NaN, NaN is returned");
}

static_assert(boost::math::ccmath::isinf(boost::math::ccmath::hypot(std::numeric_limits<T>::infinity(), T(1), T(1))));
static_assert(boost::math::ccmath::isinf(boost::math::ccmath::hypot(-std::numeric_limits<T>::infinity(), T(1), T(1))));
static_assert(boost::math::ccmath::isinf(boost::math::ccmath::hypot(T(1), std::numeric_limits<T>::infinity(), T(1))));
static_assert(boost::math::ccmath::isinf(boost::math::ccmath::hypot(T(1), -std::numeric_limits<T>::infinity(), T(1))));
static_assert(boost::math::ccmath::isinf(boost::math::ccmath::hypot(T(1), T(1), std::numeric_limits<T>::infinity())));
static_assert(boost::math::ccmath::isinf(boost::math::ccmath::hypot(T(1), T(1), -std::numeric_limits<T>::infinity())));

// Correct promoted types
if constexpr (!std::is_same_v<T, float>)
{
constexpr auto test_type = boost::math::ccmath::hypot(T(1), T(1), 1.0f);
static_assert(std::is_same_v<T, std::remove_cv_t<decltype(test_type)>>);
}
else
{
constexpr auto test_type = boost::math::ccmath::hypot(1.0f, 1, 1);
static_assert(std::is_same_v<double, std::remove_cv_t<decltype(test_type)>>);
}

// Functionality
static_assert(boost::math::ccmath::hypot(T(1), T(1), T(1)) == boost::math::ccmath::sqrt(T(3)));
static_assert(boost::math::ccmath::hypot(T(-1), T(1), T(1)) == boost::math::ccmath::sqrt(T(3)));
static_assert(boost::math::ccmath::hypot(T(2), T(2), T(1)) == T(3));
static_assert(boost::math::ccmath::hypot(T(2), T(-2), T(1)) == T(3));
static_assert(boost::math::ccmath::abs(boost::math::ccmath::hypot(T(1), T(2), T(3)) - boost::math::ccmath::sqrt(T(14))) < tol);
}

int main()
{
test<float>();
Expand All @@ -67,6 +107,13 @@ int main()
test<boost::multiprecision::float128>();
#endif

test_3_arg<float>();
test_3_arg<double>();

#ifndef BOOST_MATH_NO_LONG_DOUBLE_MATH_FUNCTIONS
test_3_arg<long double>();
#endif

return 0;
}
#else
Expand Down