std::midpoint
From cppreference.com
Defined in header <numeric> | ||
template<class T > constexpr T midpoint( T a, T b )noexcept; | (1) | (since C++20) |
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.Contents |
[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){charconst* text ="0123456789";charconst* p = text + i;charconst* 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]
[edit]See also
(C++20) | linear interpolation function (function) |
