NAME¶

std::erase,std::erase_if(std::basic_string) - std::erase,std::erase_if(std::basic_string)

Synopsis¶

Defined in header <string>
template< class CharT, class Traits, class Alloc, class U >

constexpr typename (1) (since C++20)
std::basic_string<CharT,Traits,Alloc>::size_type

erase( std::basic_string<CharT,Traits,Alloc>& c, const U& value );
template< class CharT, class Traits, class Alloc, class Pred >

constexpr typename (2) (since C++20)
std::basic_string<CharT,Traits,Alloc>::size_type

erase_if( std::basic_string<CharT,Traits,Alloc>& c, Pred pred );

1) Erases all elements that compare equal to value from the container. Equivalent to

auto it = std::remove(c.begin(), c.end(), value);
auto r = std::distance(it, c.end());
c.erase(it, c.end());
return r;

2) Erases all elements that satisfy the predicate pred from the container.
Equivalent to

auto it = std::remove_if(c.begin(), c.end(), pred);
auto r = std::distance(it, c.end());
c.erase(it, c.end());
return r;

Parameters¶

c - container from which to erase
value - value to be removed
unary predicate which returns true if the element should be erased.

The expression pred(v) must be convertible to bool for every argument v of
pred - type (possibly const) CharT, regardless of value category, and must not
modify v. Thus, a parameter type of CharT&is not allowed
, nor is CharT unless for CharT a move is equivalent to a copy
(since C++11).

Return value¶

The number of erased elements.

Complexity¶

Linear.

Example¶

// Run this code

#include <iostream>
#include <numeric>
#include <string_view>
#include <string>

void print_container(std::string_view comment, const std::string& c)
{
std::cout << comment << "{ ";
for (auto x : c) {
std::cout << x << ' ';
}
std::cout << "}\n";
}

int main()
{
std::string cnt(10, ' ');
std::iota(cnt.begin(), cnt.end(), '0');
print_container("Initially, cnt = ", cnt);

std::erase(cnt, '3');
print_container("After erase '3', cnt = ", cnt);

auto erased = std::erase_if(cnt, [](char x) { return (x - '0') % 2 == 0; });
print_container("After erase all even numbers, cnt = ", cnt);
std::cout << "Erased even numbers: " << erased << '\n';
}

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

See also¶

remove removes elements satisfying specific criteria
remove_if (function template)