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 std::basic_string<CharT, Traits, Alloc>::size_type (since C++20)
(until C++26)
erase( std::basic_string<CharT, Traits, Alloc>& c, const
U& value );
template< class CharT, class Traits, class Alloc, class U =
CharT >

constexpr std::basic_string<CharT, Traits, Alloc>::size_type (1) (since C++26)

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

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

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 = c.end() - it;
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 = c.end() - it;
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.

Notes¶

Feature-test macro Value Std Feature
__cpp_lib_algorithm_default_value_type 202403 (C++26) List-initialization for
algorithm (1)

Example¶

// Run this code

#include <iomanip>
#include <iostream>
#include <string>

int main()
{
std::string word{"startling"};
std::cout << "Initially, word = " << std::quoted(word) << '\n';

std::erase(word, 'l');
std::cout << "After erase 'l': " << std::quoted(word) << '\n';

auto erased = std::erase_if(word, [](char x)
{
return x == 'a' or x == 'r' or x == 't';
});

std::cout << "After erase all 'a', 'r', and 't': " << std::quoted(word) << '\n';
std::cout << "Erased symbols count: " << erased << '\n';
}

Output:¶

Initially, word = "startling"
After erase 'l', word = "starting"
After erase all 'a', 'r', and 't': "sing"
Erased symbols count: 4

See also¶

remove removes elements satisfying specific criteria
remove_if (function template)