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

Since C++26

Header: <string>

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;

# Declarations

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

(since C++20) (until C++26)

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

(since C++26)

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

(since C++20)

# 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 pred(v) must be convertible to bool for every argument v of 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.

# Notes

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

# Example

#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';
 
#if __cpp_lib_algorithm_default_value_type
    std::erase(word, {'g'});
    std::cout << "After erase {'g'}: " << std::quoted(word) << '\n';
#endif
}