std::experi...al::function(3)

🦋 NAME 🦋

okay bestie, meet std::experimental::function — yes that's the whole name section, it literally just says its own name back at you 💅. This page lives in the C++ Standard Libary manual (section 3), and we're gonna get you comfy with it, fr fr.

---

✨ Synopsis ✨

So first things first, it's chillin' in this header:

Defined in header <experimental/functional>

and here's the shape of it — the primary template is lowkey undefined, which is giving "do not touch" energy:

template< class >
class function; /* undefined */

template< class R, class... Args >
class function<R(Args...)>

both of those are (library fundamentals TS) by the way 🫶

And what is it? Okay so — std::experimental::function is a modified version of std::function with support for type-erased allocators. That's the whole glow-up. Periodt. 👑

---

🎀 Member types 🎀

• allocator_type — defined as std::experimental::erased_type (library fundamentals TS) — until library fundamentals TS v3
• allocator_type — defined as std::pmr::polymorphic_allocator<> (library fundamentals TS v3) 🦋

(yes, allocator_type shows up twice — the definition switches over at TS v3, iykyk)

---

💖 Member functions 💖

• constructor — constructs a new std::experimental::function instance (public member function)
• operator= — assigns a new target (public member function)
• swap — swaps the contents (public member function)
• get_memory_resource — retrieves a pointer to the memory resource used by this object to allocate memory (public member function) — removed in library fundamentals TS v3 ⚰️
• get_allocator — retrieves a type-erased std::pmr::polymorphic_allocator used by this object to allocate memory (public member function) — library fundamentals TS v3 ✨

---

🌸 Non-member functions 🌸

• std::experimental::swap(std::experimental::function) — specializes the swap algorithm (function template)
• operator== / operator!= — compares an std::experimental::function with nullptr (function template) — removed in library fundamentals TS v3 💀

---

🧚 Helper classes 🧚

• std::uses_allocator<std::experimental::function> — specializes the std::uses_allocator type trait (class template specialization) — removed in library fundamentals TS v3 🌈

---

👑 Members identical to std::function 👑

bestie, everything under here is the same as std::function — no cap, it's a straight carryover 🫶

⭐ Member types ⭐

• result_type — R

🍓 Member types removed in Library Fundamental TS v3 🍓

• argument_type — T if sizeof...(Args) == 1 and T is the first and only type in Args...
• first_argument_type — T1 if sizeof...(Args) == 2 and T1 is the first of the two types in Args...
• second_argument_type — T2 if sizeof...(Args) == 2 and T2 is the second of the two types in Args...

little note: member types argument_type, first_argument_type, and second_argument_type are removed, because the corresponding member types of std::function are removed in C++20. they're gone-gone, (library fundamentals TS v3) said so 🙈

💜 Member functions 💜

• destructor — destroys a std::function instance (public member function of std::function<R(Args...)>)
• operator bool — checks if a target is contained (public member function of std::function<R(Args...)>)
• operator() — invokes the target (public member function of std::function<R(Args...)>)

🌈 Target access 🌈

• target_type — obtains the typeid of the stored target (public member function of std::function<R(Args...)>)
• target — obtains a pointer to the stored target (public member function of std::function<R(Args...)>)

---

okay that's the whole page and you ate it up, I'm so proud 😭💖 this came from cppreference.com, dated 2024.06.10, and it's the std::experi...al::function(3) page of the C++ Standard Libary manual — go forth and allocator-erase, bestie 🎀🦋✨