std::erase,std::erase_if(std::list)

From cppreference.com

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

[edit]

Containers library

node-handle (C++17)
Sequence
array (C++11)
vector
vector<bool>
inplace_vector (C++26)
hive (C++26)
deque
forward_list (C++11)
list
Associative
set
multiset
map
multimap
Unordered associative
unordered_set (C++11)
unordered_multiset (C++11)
unordered_map (C++11)
unordered_multimap (C++11)
Adaptors
stack
queue
priority_queue
flat_set (C++23)
flat_multiset (C++23)
flat_map (C++23)
flat_multimap (C++23)
Views
span (C++20)
mdspan (C++23)
Tables
Iterator invalidation
Member function table
Non-member function table

[edit]

std::list

Member functions

list::list
list::~list
list::operator=
list::assign
list::assign_range (C++23)
list::get_allocator
Element access
list::front
list::back
Iterators
list::beginlist::cbegin (C++11)
list::endlist::cend (C++11)
list::rbeginlist::crbegin (C++11)
list::rendlist::crend (C++11)
Capacity
list::size
list::empty
list::max_size

Modifiers
list::clear
list::insert
list::insert_range (C++23)
list::emplace (C++11)
list::erase
list::push_front
list::emplace_front (C++11)
list::prepend_range (C++23)
list::pop_front
list::push_back
list::emplace_back (C++11)
list::append_range (C++23)
list::pop_back
list::resize
list::swap
Operations
list::merge
list::splice
list::removelist::remove_if
list::reverse
list::unique
list::sort

Non-member functions

operator==operator<=> (C++20)
swap(std::list)
erase(std::list)erase_if(std::list) (C++20)(C++20)

operator!=operator<operator>operator<=operator>=

(until C++20)(until C++20)(until C++20)(until C++20)(until C++20)

Deduction guides(C++17)

[edit]

Defined in header`<list>`
	(1)
template<class T,class Alloc,class U> typenamestd::list<T, Alloc>::size_type erase(std::list<T, Alloc>& c,const U& value);			(since C++20) (until C++26)
template<class T,class Alloc,class U= T> constexprtypenamestd::list<T, Alloc>::size_type erase(std::list<T, Alloc>& c,const U& value);			(since C++26)
template<class T,class Alloc,class Pred> typenamestd::list<T, Alloc>::size_type erase_if(std::list<T, Alloc>& c, Pred pred);		(2)	(since C++20) (constexpr since C++26)

1) Erases all elements that compare equal tovalue from the containerc. Equivalent toreturn c.remove_if([&](constauto& elem)->bool{return elem== value;});.

2) Erases all elements that satisfy the predicatepred from the containerc. Equivalent toreturn c.remove_if(pred);.

[edit]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 expressionpred(v) must be convertible tobool for every argument`v` of type (possibly const)`T`, regardless ofvalue category, and must not modify`v`. Thus, a parameter type ofT&is not allowed, nor isT unless for`T` a move is equivalent to a copy(since C++11).

[edit]Return value

The number of erased elements.

[edit]Complexity

Linear.

Notes

Unlikestd::list::remove,erase accepts heterogeneous types and does not force a conversion to the container's value type before invoking the== operator.

Feature-test macro	Value	Std	Feature
`__cpp_lib_algorithm_default_value_type`	`202403`	(C++26)	List-initialization for`std::erase`

[edit]Example

Run this code

#include <complex>#include <iostream>#include <numeric>#include <string_view>#include <list> void println(std::string_view comment,constauto& c){std::cout<< comment<<'[';bool first{true};for(constauto& x: c)std::cout<<(first? first=false,"":", ")<< x;std::cout<<"]\n";} int main(){std::list<char> cnt(10);std::iota(cnt.begin(), cnt.end(),'0');    println("Initially, cnt = ", cnt); std::erase(cnt,'3');    println("After erase '3', cnt = ", cnt); auto erased=std::erase_if(cnt,[](char x){return(x-'0')%2==0;});    println("After erase all even numbers, cnt = ", cnt);std::cout<<"Erased even numbers: "<< erased<<'\n'; std::list<std::complex<double>> nums{{2,2},{4,2},{4,8},{4,2}};#ifdef __cpp_lib_algorithm_default_value_typestd::erase(nums,{4,2});#elsestd::erase(nums,std::complex<double>{4,2});#endif    println("After erase {4, 2}, nums = ", nums);}

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: 5After erase {4, 2}, nums = [(2,2), (4,8)]

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
LWG 4135	C++20	the return type of the lambda predicate used was deduced from predicate arguments	the return type is explicitly specified asbool

[edit]See also

removeremove_if	removes elements satisfying specific criteria (function template)[edit]
ranges::removeranges::remove_if (C++20)(C++20)	removes elements satisfying specific criteria (algorithm function object)[edit]
removeremove_if	removes elements satisfying specific criteria (public member function)[edit]