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

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< cpp‎ | container‎ | deque

Defined in header `<deque>` |  |
template< class T, class Alloc, class U > typename std::deque<T, Alloc>::size_type erase( std::deque<T, Alloc>& c, const U& value ); | (1) | (since C++20)
template< class T, class Alloc, class Pred > typename std::deque<T, Alloc>::size_type erase_if( std::deque<T, 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 = std::distance(it, c.end());
    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 = std::distance(it, c.end());
    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 C++11). ​

### Return value

The number of erased elements.

### Complexity

Linear.

### Example

Run this code

    #include <iostream>
    #include <numeric>
    #include <string_view>
    #include <deque>

    void print_container(std::string_view comment, const std::deque<char>& c)
    {
        std::cout << comment << "{ ";
        for (char x : c)
            std::cout << x << ' ';
        std::cout << "}\n";
    }

    int main()
    {
        std::deque<char> cnt(10);
        std::iota(cnt.begin(), cnt.end(), '0');
        print_container("Initially, cnt = ", cnt);

        std::erase(cnt, '3');
        print_container("After erase '3', cnt = ", cnt);

        auto erased = std::erase_if(cnt, [](char x) { return (x - '0') % 2 == 0; });
        print_container("After erase all even numbers, cnt = ", cnt);
        std::cout << "Erased even numbers: " << erased << '\n';
    }

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

### See also

remove remove_if | removes elements satisfying specific criteria (function template)

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