std::midpoint
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Numerics library
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Bit manipulation (C++20)
Saturation arithmetic (C++26)
(C++17)
(C++17)
midpoint
(C++20)
(C++20)
(C++17)
(C++17)
(C++17)
(C++17)
(C++17)
(C++17)
(C++26)
Defined in header
<numeric>
template< class T >
constexpr T midpoint( T a, T b ) noexcept;
(1)
(since C++20)
constexpr T midpoint( T a, T b ) noexcept;
template< class T >
constexpr T* midpoint( T* a, T* b );
(2)
(since C++20)
constexpr T* midpoint( T* a, T* b );
Computes the midpoint of the integers, floating-points, or pointers a and b.
1) This overload participates in overload resolution only if
T is an arithmetic type other than bool.2) This overload participates in overload resolution only if
T is an object type. Use of this overload is ill-formed if T is an incomplete type.[edit] Parameters
a, b
-
integers, floating-points, or pointer values
[edit] Return value
1) Half the sum of a and b. No overflow occurs. If a and b have integer type and the sum is odd, the result is rounded towards a. If a and b have floating-point type, at most one inexact operation occurs.
2) If a and b point to, respectively, x[i] and x[j] of the same array object
x (for the purpose of pointer arithmetic), returns a pointer to x[i + (j - i) / 2] (or, equivalently x[std::midpoint(i, j)]) where the division rounds towards zero. If a and b do not point to elements of the same array object, the behavior is undefined.[edit] Exceptions
Throws no exceptions.
[edit] Notes
Overload (2) can be simply implemented as return a + (b - a) / 2; on common platforms. However, such implementation is not guaranteed to be portable, because there may be some platforms where creating an array with number of elements greater than PTRDIFF_MAX is possible, and b - a may result in undefined behavior even if both b and a point to elements in the same array.
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
__cpp_lib_interpolate |
201902L |
(C++20) | std::lerp , std::midpoint
|
[edit] Example
Run this code
#include <cstdint> #include <iostream> #include <limits> #include <numeric> int main() { std::uint32_t a = std::numeric_limits <std::uint32_t >::max(); std::uint32_t b = std::numeric_limits <std::uint32_t >::max() - 2; std::cout << "a: " << a << '\n' << "b: " << b << '\n' << "Incorrect (overflow and wrapping): " << (a + b) / 2 << '\n' << "Correct: " << std::midpoint(a, b) << "\n\n"; auto on_pointers = [](int i, int j) { char const* text = "0123456789"; char const* p = text + i; char const* q = text + j; std::cout << "std::midpoint('" << *p << "', '" << *q << "'): '" << *std::midpoint(p, q) << "'\n"; }; on_pointers(2, 4); on_pointers(2, 5); on_pointers(5, 2); on_pointers(2, 6); }
Output:
a: 4294967295
b: 4294967293
Incorrect (overflow and wrapping): 2147483646
Correct: 4294967294
std::midpoint('2', '4'): '3'
std::midpoint('2', '5'): '3'
std::midpoint('5', '2'): '4'
std::midpoint('2', '6'): '4'[edit] References
- C++23 standard (ISO/IEC 14882:2024):
- 27.10.16 Midpoint [numeric.ops.midpoint]
- C++20 standard (ISO/IEC 14882:2020):
- 25.10.15 Midpoint [numeric.ops.midpoint]