std::forward_list::sort(3)

🌸 std::forward_list::sort 🌸

okay so bestie, this is the std::forward_list::sort page from the C++ Standard Libary manual (section 3, yes the manual spells it “Libary” and we respect the lore 💅). It’s the glow-up sorting member function for std::forward_list, and it is so good at keeping equivalent elements in their original order.

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💖 NAME 💖

std::forward_list::sort - std::forward_list::sort

✨ Synopsis ✨

void sort();               (1) (since C++11)
template< class Compare >  (2) (since C++11)
void sort( Compare comp );

Sorts the elements and preserves the order of equivalent elements. No references or iterators become invalidated.

1. Elements are compared using operator<.
2. Elements are compared using comp.

⚠️ If an exception is thrown, the order of elements in *this is unspecified. (!!)

💅 Parameters 💅

• comp — a comparison function object (i.e. an object that satisfies the requirements of Compare) which returns true if the first argument is less than (i.e. is ordered before) the second.

The signature of the comparison function should be equivalent to the following:

bool cmp(const Type1& a, const Type2& b);

While the signature does not need to have const&, the function must not modify the objects passed to it and must be able to accept all values of type (possibly const) Type1 and Type2 regardless of value category (thus, Type1& is not allowed, nor is Type1 unless for Type1 a move is equivalent to a copy (since C++11)). The types Type1 and Type2 must be such that an object of type forward_list<T,Allocator>::const_iterator can be dereferenced and then implicitly converted to both of them.

🌈 Type requirements 🌈

• Compare must meet the requirements of Compare.

🎀 Return value 🎀

(none)

🔥 Complexity 🔥

Given \(\scriptsize N\)N as std::distance(begin(), end()):

1. Approximately \(\scriptsize N \cdot log(N)\)N·log(N) comparisons using operator<.
2. Approximately \(\scriptsize N \cdot log(N)\)N·log(N) applications of the comparison function comp.

🦋 Notes 🦋

std::sort requires random access iterators and so cannot be used with forward_list. This function also differs from std::sort in that it does not require the element type of the forward_list to be swappable, preserves the values of all iterators, and performs a stable sort.

⭐ Example ⭐

// Run this code

#include <functional>
#include <iostream>
#include <forward_list>

std::ostream& operator<<(std::ostream& ostr, const std::forward_list<int>& list)
{
    for (const int i : list)
        ostr << ' ' << i;
    return ostr;
}

int main()
{
    std::forward_list<int> list{8, 7, 5, 9, 0, 1, 3, 2, 6, 4};
    std::cout << "initially: " << list << '\n';

    list.sort();
    std::cout << "ascending: " << list << '\n';

    list.sort(std::greater<int>());
    std::cout << "descending:" << list << '\n';
}

💬 Output: 💬

initially:  8 7 5 9 0 1 3 2 6 4
ascending:  0 1 2 3 4 5 6 7 8 9
descending: 9 8 7 6 5 4 3 2 1 0

👀 See also 👀

• reverse — reverses the order of the elements (public member function).

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source/version/date bestie: http://cppreference.com, 2024.06.10, and the page is std::forward_list::sort(3) 💖🧚✨