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

From cppreference.com

Defined in header `<string>`
	(1)
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 ) ;		(2)	(since C++20)

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
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.

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

Possible output:

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

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Null-terminated strings
Byte strings
Multibyte strings
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Classes
basic_string
basic_string_view (C++17)
char_traits

remove remove_if	removes elements satisfying specific criteria (function template)
ranges::remove ranges::remove_if (C++20) (C++20)	removes elements satisfying specific criteria (algorithm function object)