std::midpoint - cppreference.com (original) (raw)

Defined in header
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

#include #include #include #include   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

[edit] See also

| | linear interpolation function (function) [edit] | | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |