constexpr modf

doc/sf/ccmath.qbk

@@ -109,6 +109,9 @@ All of the following functions require C++17 or greater.
         template <typename Integer>
         inline constexpr double trunc(Integer arg) noexcept
 
+        template <typename Real>
+        inline constexpr Real modf(Real x, Real* iptr) noexcept
+
     } // Namespaces
 
 [endsect] [/section:ccmath Constexpr CMath]

include/boost/math/ccmath/ccmath.hpp

@@ -24,5 +24,6 @@
 #include <boost/math/ccmath/floor.hpp>
 #include <boost/math/ccmath/ceil.hpp>
 #include <boost/math/ccmath/trunc.hpp>
+#include <boost/math/ccmath/modf.hpp>
 
 #endif // BOOST_MATH_CCMATH_HPP

include/boost/math/ccmath/modf.hpp

@@ -0,0 +1,77 @@
+//  (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)
+
+#ifndef BOOST_MATH_CCMATH_MODF_HPP
+#define BOOST_MATH_CCMATH_MODF_HPP
+
+#include <cmath>
+#include <limits>
+#include <type_traits>
+#include <boost/math/tools/is_constant_evaluated.hpp>
+#include <boost/math/ccmath/abs.hpp>
+#include <boost/math/ccmath/isinf.hpp>
+#include <boost/math/ccmath/isnan.hpp>
+#include <boost/math/ccmath/trunc.hpp>
+
+namespace boost::math::ccmath {
+
+namespace detail {
+
+template <typename Real>
+inline constexpr Real modf_error_impl(Real x, Real* iptr)
+{
+    *iptr = x;
+    return boost::math::ccmath::abs(x) == Real(0) ? x :
+           x > Real(0) ? Real(0) : -Real(0);
+}
+
+template <typename Real>
+inline constexpr Real modf_nan_impl(Real x, Real* iptr)
+{
+    *iptr = x;
+    return x;
+}
+
+template <typename Real>
+inline constexpr Real modf_impl(Real x, Real* iptr)
+{
+    *iptr = boost::math::ccmath::trunc(x);
+    return (x - *iptr);
+}
+
+} // Namespace detail
+
+template <typename Real>
+inline constexpr Real modf(Real x, Real* iptr)
+{
+    if(BOOST_MATH_IS_CONSTANT_EVALUATED(x))
+    {
+        return boost::math::ccmath::abs(x) == Real(0) ? detail::modf_error_impl(x, iptr) :
+               boost::math::ccmath::isinf(x) ? detail::modf_error_impl(x, iptr) :
+               boost::math::ccmath::isnan(x) ? detail::modf_nan_impl(x, iptr) :
+               boost::math::ccmath::detail::modf_impl(x, iptr);
+    }
+    else
+    {
+        using std::modf;
+        return modf(x, iptr);
+    }
+}
+
+inline constexpr float modff(float x, float* iptr)
+{
+    return boost::math::ccmath::modf(x, iptr);
+}
+
+#ifndef BOOST_MATH_NO_LONG_DOUBLE_MATH_FUNCTIONS
+inline constexpr long double modfl(long double x, long double* iptr)
+{
+    return boost::math::ccmath::modf(x, iptr);
+}
+#endif
+
+} // Namespaces
+
+#endif // BOOST_MATH_CCMATH_MODF_HPP

test/Jamfile.v2

@@ -138,6 +138,7 @@ test-suite special_fun :
    [ run ccmath_floor_test.cpp ../../test/build//boost_unit_test_framework : : : [ requires cxx17_if_constexpr ] ]
    [ run ccmath_ceil_test.cpp ../../test/build//boost_unit_test_framework : : : [ requires cxx17_if_constexpr ] ]
    [ run ccmath_trunc_test.cpp ../../test/build//boost_unit_test_framework : : : [ requires cxx17_if_constexpr ] ]
+   [ run ccmath_modf_test.cpp ../../test/build//boost_unit_test_framework : : : [ requires cxx17_if_constexpr ] ]
    [ run log1p_expm1_test.cpp test_instances//test_instances pch_light ../../test/build//boost_unit_test_framework  ]
    [ run powm1_sqrtp1m1_test.cpp test_instances//test_instances pch_light ../../test/build//boost_unit_test_framework  ]
    [ run special_functions_test.cpp ../../test/build//boost_unit_test_framework  ]

test/ccmath_modf_test.cpp

@@ -0,0 +1,98 @@
+//  (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)
+
+#include <cmath>
+#include <cfloat>
+#include <cstdint>
+#include <limits>
+#include <utility>
+#include <type_traits>
+#include <boost/math/ccmath/modf.hpp>
+#include <boost/math/ccmath/isnan.hpp>
+#include <boost/math/ccmath/isinf.hpp>
+
+#ifdef BOOST_HAS_FLOAT128
+#include <boost/multiprecision/float128.hpp>
+#endif
+
+template <typename T>
+inline constexpr T floating_point_value(const T val)
+{
+    T i = 0;
+    const T ans = boost::math::ccmath::modf(val, &i);
+
+    return ans;
+}
+
+template <typename T>
+inline constexpr T integral_value(const T val)
+{
+    T i = 0;
+    boost::math::ccmath::modf(val, &i);
+
+    return i;
+}
+
+template <typename T>
+inline constexpr std::pair<T, T> pair_value(const T val)
+{
+    T i = 0;
+    T ans = boost::math::ccmath::modf(val, &i);
+
+    return std::make_pair(i, ans);
+}
+
+template <typename T>
+constexpr void test()
+{
+    if constexpr (std::numeric_limits<T>::has_quiet_NaN)
+    {
+        constexpr std::pair<T, T> NaN_val = pair_value(std::numeric_limits<T>::quiet_NaN());
+        static_assert(boost::math::ccmath::isnan(NaN_val.first));
+        static_assert(boost::math::ccmath::isnan(NaN_val.second));
+    }
+
+    // if x is +-0, +-0 is returned and +-0 is stored in *iptr
+    static_assert(floating_point_value(T(0)) == 0);
+    static_assert(floating_point_value(-T(0)) == -0);
+    static_assert(integral_value(T(0)) == 0);
+    static_assert(integral_value(-T(0)) == -0);
+
+    // if x is +- inf, +-0 is returned and +-inf is stored in *iptr
+    static_assert(floating_point_value(std::numeric_limits<T>::infinity()) == 0);
+    static_assert(floating_point_value(-std::numeric_limits<T>::infinity()) == -0);
+    static_assert(integral_value(std::numeric_limits<T>::infinity()) == std::numeric_limits<T>::infinity());
+    static_assert(integral_value(-std::numeric_limits<T>::infinity()) == -std::numeric_limits<T>::infinity());
+
+    // The returned value is exact, the current rounding mode is ignored
+    // The return value and *iptr each have the same type and sign as x
+    static_assert(integral_value(T(123.45)) == 123);
+    static_assert(integral_value(T(-234.56)) == -234);
+    static_assert(floating_point_value(T(1.0/2)) == T(1.0/2));
+    static_assert(floating_point_value(T(-1.0/3)) == T(-1.0/3));
+}
+
+#if !defined(BOOST_MATH_NO_CONSTEXPR_DETECTION) && !defined(BOOST_MATH_USING_BUILTIN_CONSTANT_P)
+int main()
+{
+    test<float>();
+    test<double>();
+
+    #ifndef BOOST_MATH_NO_LONG_DOUBLE_MATH_FUNCTIONS
+    test<long double>();
+    #endif
+
+    #ifdef BOOST_HAS_FLOAT128
+    test<boost::multiprecision::float128>();
+    #endif
+
+    return 0;
+}
+#else
+int main()
+{
+    return 0;
+}
+#endif

test/compile_test/ccmath_modf_incl_test.cpp

@@ -0,0 +1,21 @@
+//  (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)
+
+#include <boost/math/ccmath/modf.hpp>
+#include "test_compile_result.hpp"
+
+void compile_and_link_test()
+{
+   float i_f;
+   check_result<float>(boost::math::ccmath::modf(1.0f, &i_f));
+
+   double i_d;
+   check_result<double>(boost::math::ccmath::modf(1.0, &i_d));
+
+#ifndef BOOST_MATH_NO_LONG_DOUBLE_MATH_FUNCTIONS
+   long double i_ld;
+   check_result<long double>(boost::math::ccmath::modf(1.0l, &i_ld));
+#endif
+}