std::midpoint
From cppreference.com
Defined in header <numeric>
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template
<
class T >
constexpr T midpoint( T a, T b ) noexcept ; |
(1) | (since C++20) |
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template
<
class T >
constexpr T* midpoint( T* a, T* b ) ; |
(2) | (since C++20) |
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
Parameters
| a, b | - | integers, floating-points, or pointer values |
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
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
Exceptions
Throws no exceptions.
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
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
__cpp_lib_interpolate |
201902L |
(C++20) | std::lerp, std::midpoint
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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'
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]
See also
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(C++20)
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linear interpolation function (function) |