Add noexcept and fix is_representable for signed types

boostorg · Mar 17, 2023 · 8b9727a · 8b9727a
1 parent 5284fb7
commit 8b9727a
Showing 1 changed file with 6 additions and 3 deletions.
diff --git a/include/boost/math/special_functions/round.hpp b/include/boost/math/special_functions/round.hpp
@@ -24,7 +24,7 @@ namespace detail{
 
 // https://stackoverflow.com/questions/8905246/how-to-check-if-float-can-be-exactly-represented-as-an-integer/17822304#17822304
 template <typename T, typename ResultType>
-inline ResultType float_to_int(T x)
+inline ResultType float_to_int(T x) noexcept
 {
    BOOST_MATH_STD_USING
 
@@ -45,10 +45,13 @@ inline ResultType float_to_int(T x)
 }
 
 template <typename T, typename TargetType>
-inline bool is_representable(T x)
+inline bool is_representable(T x) noexcept
 {
    BOOST_MATH_STD_USING
-   return (floor(x) == x && x >= static_cast<T>(0.0L) && x < ldexp(static_cast<T>(1.0L), sizeof(TargetType) * CHAR_BIT));
+   constexpr int sign = std::is_signed<ResultType>::value ? -1 : 0;
+   return (floor(x) == x && 
+           x >= static_cast<T>(0.0L) && 
+           x < (ldexp(static_cast<T>(1.0L), (sizeof(TargetType) * CHAR_BIT) + sign) + sign));
 }
 
 template <class T, class Policy>