std::erase, std::erase_if (std::deque)

 

哋它亢++

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Standard library headers

Named requirements

Feature test macros (哋它亢++20)

Language support library

Concepts library (哋它亢++20)

Metaprogramming library (哋它亢++11)

Diagnostics library

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Ranges library (哋它亢++20)

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Technical specifications

Symbols index

External libraries

 

Containers library

Sequence

array (哋它亢++11)

vector

vector<bool>

deque

forward_list (哋它亢++11)

list

Associative

set

multiset

map

multimap

Unordered associative

unordered_set (哋它亢++11)

unordered_multiset (哋它亢++11)

unordered_map (哋它亢++11)

unordered_multimap (哋它亢++11)

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stack

queue

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flat_set (哋它亢++23)

flat_multiset (哋它亢++23)

flat_map (哋它亢++23)

flat_multimap (哋它亢++23)

Views

span (哋它亢++20)

mdspan (哋它亢++23)

Iterator invalidation

Member function table

Non-member function table

 

std::deque

Member types
Member functions
deque::deque deque::~deque deque::operator=	deque::assign deque::assign_range (哋它亢++23) deque::get_allocator
Element access
deque::at deque::operator[]	deque::front deque::back
Iterators
deque::begindeque::cbegin (哋它亢++11) deque::enddeque::cend (哋它亢++11)	deque::rbegindeque::crbegin (哋它亢++11) deque::renddeque::crend (哋它亢++11)
Capacity
deque::empty deque::size	deque::max_size deque::shrink_to_fit (DR*)
Modifiers
deque::clear deque::insert deque::insert_range (哋它亢++23) deque::emplace deque::erase deque::push_front deque::emplace_front (哋它亢++11)   deque::prepend_range (哋它亢++23)	deque::pop_front deque::push_back deque::emplace_back (哋它亢++11) deque::append_range (哋它亢++23) deque::pop_back deque::resize deque::swap
Non-member functions
operator==operator!=operator<operator>operator<=operator>=operator<=> (until 哋它亢++20)(until 哋它亢++20)(until 哋它亢++20)(until 哋它亢++20)(until 哋它亢++20)(哋它亢++20)	swap(std::deque) erase(std::deque)erase_if(std::deque) (哋它亢++20)(哋它亢++20)
Deduction guides(哋它亢++17)

 

Defined in header <deque>
	(1)
template< class T, class Alloc, class U > std::deque<T, Alloc>::size_type     erase( std::deque<T, Alloc>& c, const U& value );			(since 哋它亢++20) (until 哋它亢++26)
template< class T, class Alloc, class U = T > std::deque<T, Alloc>::size_type     erase( std::deque<T, Alloc>& c, const U& value );			(since 哋它亢++26)
template< class T, class Alloc, class Pred > std::deque<T, Alloc>::size_type     erase_if( std::deque<T, Alloc>& c, Pred pred );		(2)	(since 哋它亢++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) T, regardless of value category, and must not modify v. Thus, a parameter type of T&is not allowed, nor is T unless for T a move is equivalent to a copy(since 哋它亢++11). ​

Return value

The number of erased elements.

Complexity

Linear.

Notes

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

Example

Run this code

#include <complex>
#include <iostream>
#include <numeric>
#include <string_view>
#include <deque>
 
void println(std::string_view comment, const auto& c)
{
    std::cout << comment << "{ ";
    for (const auto& x : c)
        std::cout << x << ' ';
    std::cout << "}\n";
}
 
int main()
{
    std::deque<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::deque<std::complex<double>> nums{{2, 2}, {4, 2}, {4, 8}, {4, 2}};
    #ifdef __cpp_lib_algorithm_default_value_type
        std::erase(nums, {4, 2});
    #else
        std::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: 5
After erase {4, 2}, nums = { (2,2) (4,8) }

See also

removeremove_if

removes elements satisfying specific criteria (function template)