std::erase, std::erase_if(std::hive)
From cppreference.com
| Defined in header <hive>
|
||
template< class T, class Allocator, class U = T >
typename hive<T, Allocator>::size_type
erase( hive<T, Allocator>& c, const U& value );
|
(1) | (since C++26) |
template< class T, class Allocator, class Predicate >
typename hive<T, Allocator>::size_type
erase_if( hive<T, Allocator>& c, Predicate pred );
|
(2) | (since C++26) |
1) Erases all elements that compare equal to
value from the container. Equivalent to
return std::erase_if(c, [&](const auto& elem) -> bool { return elem == value; });
2) Erases all elements that satisfy the predicate
pred from the container. Equivalent to
auto original_size = c.size();
for (auto i = c.begin(); i != c.end(); )
if (pred(*i))
i = c.erase(i);
else
++i;
return original_size - c.size();
Parameters
| c | - | container from which to erase |
| value | - | value to be removed |
| pred | - | unary predicate which returns true if the element should be erased. The expression |
Return value
The number of erased elements.
Complexity
Linear.
Example
Run this code
#include <complex>
#include <numeric>
#include <print>
#include <hive>
template<typename T>
struct std::formatter<std::complex<T>, char>
{
template<class ParseContext>
constexpr ParseContext::iterator parse(ParseContext& ctx)
{
return ctx.begin();
}
template<class FmtContext>
FmtContext::iterator format(const auto& s, FmtContext& ctx) const
{
auto out{std::format("({},{})", s.real(), s.imag())};
return std::ranges::copy(std::move(out), ctx.out()).out;
}
};
int main()
{
std::hive<char> cnt(10);
std::iota(cnt.begin(), cnt.end(), '0');
std::println("Initially, cnt = {}", cnt);
std::erase(cnt, '3');
std::println("After erase '3', cnt = {}", cnt);
auto erased = std::erase_if(cnt, [](char x) { return (x - '0') % 2 == 0; });
std::println("After erase all even numbers, cnt = {}", cnt);
std::println("Erased even numbers: {}", erased);
std::hive<std::complex<double>> nums{{2, 2}, {4, 2}, {4, 8}, {4, 2}};
#ifdef __cpp_lib_algorithm_default_value_type
std::erase(nums, {4, 2});
#else
std::erase(nums, std::complex<double>{4, 2});
#endif
std::println("After erase {{4, 2}}, nums = {}", nums);
}
Output:
Initially, cnt = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
After erase '3', cnt = [0, 1, 2, 4, 5, 6, 7, 8, 9]
After erase all even numbers, cnt = [1, 5, 7, 9]
Erased even numbers: 5
After erase {4, 2}, nums = [(2,2), (4,8)]
See also
| erases elements (public member function) | |
| removes elements satisfying specific criteria (function template & algorithm function object) | |
(C++20)(C++20) |