std:: midpoint
|
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 .
T
is an arithmetic type other than
bool
.
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
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.
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 point to elements in the same array.
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
__cpp_lib_interpolate
|
201902L | (C++20) |
std::lerp
,
std::midpoint
|
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'
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
|
(C++20)
|
linear interpolation function
(function) |