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

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros(C++20)

Language support library

Concepts library(C++20)

Diagnostics library

Memory management library

Metaprogramming library(C++11)

General utilities library

Containers library

Iterators library

Ranges library(C++20)

Algorithms library

Strings library

Text processing library

Numerics library

Date and time library

Input/output library

Filesystem library(C++17)

Concurrency support library(C++11)

Execution control library(C++26)

Technical specifications

Symbols index

External libraries

 

Strings library

Classes

basic_string

basic_string_view (C++17)

char_traits

 

std::basic_string

Member functions basic_string::basic_string basic_string::~basic_string basic_string::operator= basic_string::assign basic_string::assign_range (C++23)   basic_string::get_allocator Element access basic_string::at basic_string::operator[] basic_string::front (DR*) basic_string::back (DR*) basic_string::data basic_string::c_str basic_string::operator  basic_string_view (C++17) Iterators basic_string::beginbasic_string::cbegin (C++11) basic_string::endbasic_string::cend (C++11) basic_string::rbeginbasic_string::crbegin (C++11) basic_string::rendbasic_string::crend (C++11) Search basic_string::find basic_string::rfind basic_string::find_first_of basic_string::find_first_not_of basic_string::find_last_of basic_string::find_last_not_of

Modifiers basic_string::clear basic_string::insert basic_string::insert_range (C++23) basic_string::erase basic_string::push_back basic_string::pop_back (DR*) basic_string::append basic_string::append_range (C++23) basic_string::operator+= basic_string::replace basic_string::replace_with_range (C++23) basic_string::copy basic_string::resize basic_string::resize_and_overwrite (C++23)  basic_string::swap Capacity basic_string::empty basic_string::sizebasic_string::length basic_string::max_size basic_string::reserve basic_string::capacity basic_string::shrink_to_fit (DR*) Operations basic_string::compare basic_string::starts_with (C++20) basic_string::ends_with (C++20) basic_string::contains (C++23) basic_string::substr

Constants basic_string::npos Non-member functions operator+ swap(std::basic_string) erase(std::basic_string)erase_if(std::basic_string) (C++20)(C++20) I/O operator<<operator>> getline Comparison operator==operator!=operator<operator>operator<=operator>=operator<=> (until C++20)(until C++20)(until C++20)(until C++20)(until C++20)(C++20) Numeric conversions stoistolstoll (C++11)(C++11)(C++11) stoulstoull (C++11)(C++11)  stofstodstold (C++11)(C++11)(C++11) to_string (C++11) to_wstring (C++11) Literals operator""s (C++14) Helper classes hash<std::basic_string> (C++11) Deduction guides(C++17)

 

Defined in header <string>
	(1)
template<class CharT, class Traits, class Alloc, class U > constexprstd::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 > constexprstd::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 > constexprstd::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_typestd::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"

See also

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