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std::div_sat

From cppreference.com
< cpp‎ | numeric
 
 
 
Defined in header <numeric>
template< class T >
constexpr T div_sat( T x, T y ) noexcept;
(since C++26)

Computes the saturating division x / y. If T is a signed integer type, x is the smallest (most negative) value of T, and y == -1, returns the greatest value of T; otherwise, returns x / y.

y must not be 0, otherwise the behavior is undefined. The function call is not a core constant expression if undefined behavior happens.

This overload participates in overload resolution only if T is an integer type, that is: signed char, short, int, long, long long, an extended signed integer type, or an unsigned version of such types. In particular, T must not be (possibly cv-qualified) bool, char, wchar_t, char8_t, char16_t, and char32_t, as these types are not intended for arithmetic.

Contents

[edit] Parameters

x, y - integer values

[edit] Return value

Saturated x / y.

[edit] Exceptions

Throws no exceptions.

[edit] Notes

Unlike the built-in arithmetic operators on integers, the integral promotion does not apply to the x and y arguments.

If two arguments of different type are passed, the call fails to compile, i.e. the behavior relative to template argument deduction is the same as for std::min or std::max.

Most modern hardware architectures have efficient support for saturation arithmetic on SIMD vectors, including SSE2 for x86 and NEON for ARM.

Feature-test macro Value Std Feature
__cpp_lib_saturation_arithmetic 202311L (C++26) Saturation arithmetic

[edit] Possible implementation

namespace detail {
template<class T>
concept standard_or_extended_integral =
     std::is_integral_v<T> &&
    !std::is_same_v<std::remove_cv_t<T>, bool> &&
    !std::is_same_v<std::remove_cv_t<T>, char> &&
    !std::is_same_v<std::remove_cv_t<T>, char8_t> &&
    !std::is_same_v<std::remove_cv_t<T>, char16_t> &&
    !std::is_same_v<std::remove_cv_t<T>, char32_t> &&
    !std::is_same_v<std::remove_cv_t<T>, wchar_t>;
} // namespace detail
 
template<detail::standard_or_extended_integral T>
constexpr T div_sat( T x, T y ) noexcept
{
    if constexpr (std::is_signed_v<T>)
        if (x == std::numeric_limits<T>::min() && y == -1)
            return std::numeric_limits<T>::max();
    return x / y;
}

[edit] Example

Can be previewed on Compiler Explorer.

#include <climits>
#include <numeric>
 
static_assert
(""
    && (std::div_sat<int>(6, 3) == 2) // not saturated
    && (std::div_sat<int>(INT_MIN, -1) == INT_MAX) // saturated
    && (std::div_sat<unsigned>(6, 3) == 2) // not saturated
);
 
int main() {}

[edit] See also

(C++26)
saturating addition operation on two integers
(function template) [edit]
(C++26)
saturating subtraction operation on two integers
(function template) [edit]
(C++26)
saturating multiplication operation on two integers
(function template) [edit]
returns an integer value clamped to the range of a another integer type
(function template) [edit]
(C++17)
clamps a value between a pair of boundary values
(function template) [edit]
(C++20)
checks if an integer value is in the range of a given integer type
(function template) [edit]
[static]
returns the smallest finite value of the given type
(public static member function of std::numeric_limits<T>) [edit]
[static]
returns the largest finite value of the given type
(public static member function of std::numeric_limits<T>) [edit]

[edit] External links

1.  A branch-free implementation of saturation arithmetic — Locklessinc.com, 2012