61 lines
1.8 KiB
C++
61 lines
1.8 KiB
C++
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/**
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* Copyright 2020 Jonathan Bayless
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*
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* Use of this source code is governed by an MIT-style license that can be found
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* in the LICENSE file or at https://opensource.org/licenses/MIT.
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*/
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#ifndef _MATH_UTILS_HPP_
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#define _MATH_UTILS_HPP_
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#include <cmath>
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#include <iostream>
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namespace squiggles {
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/**
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* Returns the sign value of the given value.
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*
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* @return 1 if the value is positive, -1 if the value is negative, and 0 if
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* the value is 0.
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*/
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template <class T> inline int sgn(T v) {
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return (v > T(0)) - (v < T(0));
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}
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inline bool
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nearly_equal(const double& a, const double& b, double epsilon = 1e-5) {
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return std::fabs(a - b) < epsilon;
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}
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} // namespace squiggles
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namespace std {
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// Copied from https://github.com/emsr/cxx_linear
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template <typename _Float>
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constexpr std::enable_if_t<
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std::is_floating_point_v<_Float> &&
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__cplusplus <= 201703L, // Only defines this function if C++ standard < 20
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_Float>
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lerp(_Float __a, _Float __b, _Float __t) {
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if (std::isnan(__a) || std::isnan(__b) || std::isnan(__t))
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return std::numeric_limits<_Float>::quiet_NaN();
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else if ((__a <= _Float{0} && __b >= _Float{0}) ||
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(__a >= _Float{0} && __b <= _Float{0}))
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// ab <= 0 but product could overflow.
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#ifndef FMA
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return __t * __b + (_Float{1} - __t) * __a;
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#else
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return std::fma(__t, __b, (_Float{1} - __t) * __a);
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#endif
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else if (__t == _Float{1})
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return __b;
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else { // monotonic near t == 1.
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#ifndef FMA
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const auto __x = __a + __t * (__b - __a);
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#else
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const auto __x = std::fma(__t, __b - __a, __a);
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#endif
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return (__t > _Float{1}) == (__b > __a) ? std::max(__b, __x)
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: std::min(__b, __x);
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}
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}
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} // namespace std
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#endif
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