std::div_sat

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.

Parameters

x, y

-

integer values

Return value

Saturated x / y.

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() {}

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

External links

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

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