NAME¶

std::div_sat - std::div_sat

Synopsis¶

Defined in header <numeric>
template< class T > (since C++26)
constexpr T div_sat( T x, T y ) noexcept;

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.

Parameters¶

x, y - integer values

Return value¶

Saturated x / y.

Exceptions¶

Throws no exceptions.

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

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;
}

Example¶

Can be previewed on Compiler Explorer.

// Run this code

#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() {}

See also¶

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

External links¶

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