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

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< cpp‎ | container‎ | inplace vector

Defined in header `<inplace_vector>` |  |
template< class T, std::size_t N, class U = T > constexpr typename std::inplace_vector <T, N>::size_type erase( std::inplace_vector <T, N>& c, const U& value ); | (1) | (since C++26)
template< class T, std::size_t N, class Pred > constexpr typename std::inplace_vector <T, N>::size_type erase_if( std::inplace_vector <T, N>& c, Pred pred ); | (2) | (since C++26)

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 <cassert>
    #include <complex>
    #include <inplace_vector>
    #include <numeric>
    #include <print>

    int main()
    {
        std::inplace_vector<int, 10> v(10, 0);
        std::ranges::iota(v, 0);
        std::println("Initially, v = {}", v);

        auto erased = std::erase(v, 3);
        std::println("After erase(v, 3), v = {}", v);
        assert(erased == 1);

        erased = std::erase_if(v, [](int x) { return x % 2 == 0; });
        std::println("After erasing all even numbers, v = {}", v);
        std::println("Erased even numbers: {}", erased);

        std::inplace_vector<std::complex<double>> nums{{2, 2}, {4, 2}, {4, 8}, {4, 2}};
        std::erase(nums, {4, 2}); // since U = T, the value type can be ommited
        std::println("After erase {4, 2}, nums = {}", nums);
    }

Output:

    Initially, v = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
    After erase(v, 3), v = [0, 1, 2, 4, 5, 6, 7, 8, 9]
    After erasing all even numbers, v = [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)
ranges::removeranges::remove_if (C++20)(C++20) | removes elements satisfying specific criteria (algorithm function object)

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