NAME¶

std::erase_if(std::flat_set) - std::erase_if(std::flat_set)

Synopsis¶

Defined in header <flat_set>
template< class Key, class Compare, class KeyContainer,

class Pred >
std::flat_set<Key, Compare, KeyContainer>::size_type (since C++23)
erase_if( std::flat_set<Key, Compare, KeyContainer>& c,

Pred pred );

Erases all elements that satisfy the predicate pred from c.

The predicate pred is satisfied if the expression bool(pred(std::as_const(e))) is
true, where e is some element in c.

Key must be MoveAssignable. Otherwise, the behavior is undefined.

Parameters¶

c - container adaptor from which to erase
pred - predicate that returns true if the element should be erased

Return value¶

The number of erased elements.

Complexity¶

Exactly c.size() applications of the predicate pred.

Exceptions¶

If erase_if throws, c remains in valid but unspecified (maybe empty) state.

Notes¶

The algorithm is stable, that is, the order of elements that are not deleted remains
unchanged.

Example¶

// Run this code

#include <iostream>
#include <flat_set>

void println(auto rem, auto const& container)
{
std::cout << rem << '{';
for (char sep[]{0, ' ', 0}; const auto& item : container)
std::cout << sep << item, *sep = ',';
std::cout << "}\n";
}

int main()
{
std::flat_set data{3, 3, 4, 5, 5, 6, 6, 7, 2, 1, 0};
println("Original:\n", data);

auto divisible_by_3 = [](auto const& x) { return (x % 3) == 0; };

const auto count = std::erase_if(data, divisible_by_3);

println("Erase all items divisible by 3:\n", data);
std::cout << count << " items erased.\n";
}

Output:¶

Original:
{0, 1, 2, 3, 4, 5, 6, 7}
Erase all items divisible by 3:
{1, 2, 4, 5, 7}
3 items erased.

See also¶

remove removes elements satisfying specific criteria
remove_if (function template)