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Showing content from https://en.cppreference.com/w/cpp/language/../algorithm/../numeric/midpoint.html below:

std::midpoint - cppreference.com

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

.

[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.

[edit] Example 
#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
[edit] See also linear interpolation function
(function) [edit]

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