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std::midpoint(3) C++ Standard Libary std::midpoint(3) NAME std::midpoint - std::midpoint Synopsis Defined in header <numeric> template< class T > (1) (since C++20) constexpr T midpoint( T a, T b ) noexcept; template< class T > (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. 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 in- teger type and the sum is odd, the result is rounded towards a. If a and b have float- ing-point type, at most one inexact operation occurs. 2) If a and b point to, respectively, x[i] and x[j] of the same ar- ray 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 to- wards zero. If a and b do not point to elements of the same array object, the behav- ior is undefined. 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 be- havior even if both b and a point to elements in the same array. Feature-test macro: __cpp_lib_interpolate Example // Run this code #include <cstdint> #include <limits> #include <numeric> #include <iostream> 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++20 standard (ISO/IEC 14882:2020): * 25.10.15 Midpoint [numeric.ops.midpoint] See also lerp linear interpolation function (C++20) (function) http://cppreference.com 2022.07.31 std::midpoint(3)
NAME | Synopsis | Parameters | Return value | Exceptions | Notes | Example | Output: | References | See also
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