std::forward_list::resize(3)

💖 std::forward_list::resize(3) 💖

okay so bestie, welcome to the C++ Standard Libary page for std::forward_list::resize 💅 this one is lowkey simple but you will understand it, fr fr.

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✨ NAME ✨

std::forward_list::resize — std::forward_list::resize

like yes, the name is literally the name. iconic behavior tbh 🎀

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🦋 Synopsis 🦋

two overloads, both since C++11, no cap:

void resize( size_type count );                          (1) (since C++11)
void resize( size_type count, const value_type& value ); (2) (since C++11)

So this resizes the container so it holds count elements. If count == std::distance(begin(), end()) — basically if count already equals the current size — it does absolutely nothing, periodt.

If the current size is greater than count, the container gets reduced to its first count elements.

If the current size is less than count:

1. additional default-inserted elements are appended.
2. additional copies of value are appended.

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🌸 Parameters 🌸

• count — new size of the container
• value — the value to initialize the new elements with

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💜 Type requirements 💜

• T must meet the requirements of DefaultInsertable in order to use overload (1).
• T must meet the requirements of CopyInsertable in order to use overload (2).

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🫶 Return value 🫶

(none)

like, nothing. empty. no notes. 💀

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🔥 Complexity 🔥

Linear in the difference between the current size and count. Additional complexity possible due to list traversal to reach the first element to erase/the end position to insert.

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🌈 Notes 🌈

If value-initialization in overload (1) is undesirable — for example, if the elements are of non-class type and zeroing out is not needed — it can be avoided by providing a custom Allocator::construct. slay, customization 💅

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🎀 Example 🎀

// Run this code

#include <forward_list>
#include <iostream>

void print(auto rem, const std::forward_list<int>& c)
{
    for (std::cout << rem; const int el : c)
        std::cout << el << ' ';
    std::cout << '\n';
}

int main()
{
    std::forward_list<int> c = {1, 2, 3};
    print("The forward_list holds: ", c);

    c.resize(5);
    print("After resize up to 5: ", c);

    c.resize(2);
    print("After resize down to 2: ", c);

    c.resize(6, 4);
    print("After resize up to 6 (initializer = 4): ", c);
}

Output

The forward_list holds: 1 2 3
After resize up to 5: 1 2 3 0 0
After resize down to 2: 1 2
After resize up to 6 (initializer = 4): 1 2 4 4 4 4

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👑 See also 👑

• insert_after — inserts elements after an element (public member function)
• erase_after — erases an element after an element (public member function)

mwah 💋 — source: http://cppreference.com; version/date: 2024.06.10; page: std::forward_list::resize(3) 🦋