Added better null checks and assumptions. removed `is_boxed()` meta-polymorphism. added Box<T> children (non-virtual) to perform unsafe operations that may invalidate Box<T> invariant.

Fortune for libexopt's current commit: Future blessing − 末吉

include/boxed.h

@@ -10,14 +10,13 @@
 #include "exopt.h"
 
 namespace exopt::types { namespace boxed {
-
 	template<typename T>
 	struct [[gnu::visibility("internal")]]  boxable_value_type { using type = std::conditional_t
 			<std::is_reference_v<T>
 			,std::reference_wrapper<std::remove_cvref_t<T> >
 			,T>; };
 
-	namespace { 
+	namespace {
 
 	template<typename T>
 	constexpr std::unique_ptr<T> uniq_clone(std::unique_ptr<T> const& c) noexcept(std::is_nothrow_copy_constructible_v<T>) requires(std::is_copy_constructible_v<T>)
@@ -31,7 +30,7 @@ namespace exopt::types { namespace boxed {
 		requires(std::is_copy_constructible_v<T>)
 	{ if(__builtin_expect(!bool(c), false)) 
 #ifdef DEBUG
-		throw ptr::NullException{}; 
+		throw ptr::NullDerefException<T>{};
 #else
 		__builtin_unreachable(); 
 #endif
@@ -63,6 +62,94 @@ namespace exopt::types { namespace boxed {
 		{ static_cast<std::decay_t<To> &&>(from) } -> std::convertible_to<To>;
 	};
 
+	/*struct ErasedTypeDeleter { 
+		constexpr virtual ~ErasedTypeDeleter() = default;
+		constexpr ErasedTypeDeleter() noexcept = default;
+
+		constexpr virtual void apply_delete() = 0;
+		//TODO: See below...
+	};*/
+
+	template<polymorphic_castable<void> T>
+	constexpr auto uniq_erase_type(std::unique_ptr<T>&& from) noexcept {
+		struct deleter final /*: public ErasedTypeDeleter XXX <- Is this useful, for unerasing the type, maybe?*/ {
+			typedef T type;
+
+			
+			/*[[gnu::cold, noreturn, gnu::noinline]]
+			constexpr static void _throw() 
+			{
+				throw ptr::NullException{};
+			}
+		public:*/
+			constexpr void opreator()(void *p) noexcept(std::is_nothrow_destructible_v<T>) {
+			/*	T* ptr;
+				if constexpr(DOES_CHECK) {
+				 if(__builtin_expect(!(ptr = dynamic_cast<T*>(p)), false))
+					_throw();
+				} else ptr = static_cast<T*>(p); 
+				delete ptr;*/
+				delete static_cast<T*>(p);
+			}
+			constexpr T* back_cast(void *p) noexcept { return static_cast<T*>(p); }
+			constexpr deleter() noexcept = default;
+			constexpr deleter(deleter const&) noexcept = default;
+			constexpr deleter(deleter &&) noexcept = default;
+			constexpr deleter& operator=(deleter const&) noexcept = default;
+			constexpr deleter& operator=(deleter &&) noexcept = default;
+
+			constexpr ~deleter() noexcept = default;
+		};
+		return std::unique_ptr<void, deleter> {
+			// Cannot retain type information of most-derived class from this: \
+			dynamic_cast<void*>	
+			static_cast<void*>
+			(std::move(from).release())
+			
+		};
+	}
+	template<polymorphic_castable<void> T, typename D> requires(requires{ 
+		typename std::unique_ptr<T, D>;
+		requires(!std::is_same_v<std::unique_ptr<T, D>::deleter_type, std::unique_ptr<T>::deleter_type);
+	})
+	constexpr auto uniq_erase_type(std::unique_ptr<T, D>&& from) noexcept {
+		class deleter final {
+			D m_del;
+		public:
+			constexpr void operator()(void* p) noexcept(std::is_nothrow_invocable_v<D::operator(), T>) {
+				m_del(static_cast<T*>(p));
+			}
+
+			constexpr T* back_cast(void* p) noexcept { return static_cast<T*>(p); }
+
+			constexpr deleter(D&& deleter) noexcept(std::is_nothrow_move_constructible_v<D>)
+				: m_del(std::move(deleter)) {}
+
+			constexpr deleter() noexcept(std::is_nothrow_default_constructible_v<D>) requires(std::is_default_constructible_v<D>) =default;//: m_del() {}
+
+			constexpr deleter(const deleter&) noexcept(std::is_nothrow_copy_constructible_v<D>) = default;
+			constexpr deleter(deleter&&) noexcept(std::is_nothrow_move_constructible_v<D>) = default;
+
+			constexpr deleter& operator=(const deleter&) noexcept(std::is_nothrow_copy_assignable_v<D>) = default;
+			constexpr deleter& operator=(deleter&&) noexcept(std::is_nothrow_move_assignable_v<D>) = default;
+
+			constexpr ~deleter() noexcept(std::is_nothrow_destructible_v<D>) requires(std::is_trivially_destructible_v<D>) = default;
+			constexpr ~deleter() noexcept(std::is_nothrow_destructible_v<D>) {}
+		};
+		if constexpr(std::is_default_constructible_v<D>)
+			return std::unique_ptr<void, deleter> {
+				static_cast<void*>
+				(std::move(from).release()), deleter()
+			};
+		else {
+			deleter&& del{std::move(from.get_deleter())};
+			return std::unique_ptr<void, deleter> {
+				static_cast<void*>
+				(std::move(from).release()), deleter{std::move(del)}
+			};
+		}
+	}
+
 	template<typename To, typename From> requires(polymorphic_castable<From, To>)
 	constexpr std::unique_ptr<To> static_uniq_cast(std::unique_ptr<From>&& from) noexcept
 	{
@@ -86,25 +173,8 @@ namespace exopt::types { namespace boxed {
 		else return static_uniq_cast(std::move(from));
 	}
 
-#if 0
-//TODO: Cannot be implemented with this method
-	constexpr bool is_boxed_value(auto const& value) noexcept {
-		return bool(dynamic_cast<ObjectBase const*>(std::addressof(value)));
-	}
-	template<typename T>
-	constexpr bool is_boxed_type() noexcept {
-		using type = std::remove_reference_t<T>;
-		constexpr type const* VALUE = nullptr;
-		return bool(dynamic_cast<ObjectBase const*>(VALUE));
-	}
-
-// We need either: Tagged pointers (XOR, bit-mangled, manual heap, or GOT (external allocation) kind), \
-	or (preferred): layout of Box<T> to be `{ aligned<T>(T, box_type_tag) } unique*` \
-		box_type_tag should be: One pointer width, starting at offset *T+1 (aligned to T within internal tuple struct), provides a way to access RTTI for `*T`, a pointer to static (non-allocated) type information or dynamic_cast used lambda would be ideal.
-#endif
-
 	template<typename T>
-	struct Box final {
+	struct alignas(std::unique_ptr<T>) Box {
 		typedef boxable_value_type<T>::type type;
 
 		template<std::derived_from<T> U, bool RuntimeCheck=false>
@@ -150,15 +220,24 @@ namespace exopt::types { namespace boxed {
 		}
 
 		[[gnu::nonnull(1)]]
-		constexpr static Box<T> from_raw_ptr(T* ptr) noexcept {
+		constexpr static Box<T> from_raw_ptr(T* ptr) noexcept(!_EO(DEBUG)) {
+#if DEBUG
+			ptr::throw_if_null(ptr);
+#endif
 			return Box<T>{ std::unique_ptr<T>{ ptr } };
 		}
-		constexpr static Box<T> from_raw_ptr(std::unique_ptr<T>&& uniq) 
+
+		constexpr static Box<T> from_raw_ptr(std::unique_ptr<T>&& uniq) {
+			if(__builtin_expect(!bool(uniq), false)) ptr::throw_null_exception<T>();
+			_EO_ASSUME(uniq.get() != nullptr);
+			return Box<T> { std::move(uniq) };
+		}
+
+		constexpr static Box<T> from_raw_ptr_unchecked(std::unique_ptr<T>&& uniq) noexcept(!_EO(DEBUG)) {
 #if DEBUG
-			{ if(__builtin_expect(!uniq, false)) throw ptr::NullException{};
+			if(__builtin_expect(!uniq, false)) ptr::throw_null_exception<T>(); 
 #else
 
-			noexcept {
 			_EO_ASSUME(uniq.get() != nullptr);
 #endif
 			return Box<T>{ std::move(uniq) };
@@ -173,40 +252,63 @@ namespace exopt::types { namespace boxed {
 	//TODO: Accessors, `(explicit?) operator std::unique_ptr<T> const&[&]`?, etc.
 
 		constexpr ~Box() = default;
+	protected:
+		// For types that may need to invalidate the Box<T> guarantee without exposing it in API, they can inherit (non-virtual). 
+
+		// For unsafe operations, wether or not to apply checks.
+		enum unsafe_t {
+			UNSAFE,
+		};
+		enum maybe_unsafe_t {
+			CHECKED,
+			DEBUG_CHECKED,
+		};
+
+		constexpr Box(util::exact_type<unsafe_t> auto u, std::unique_ptr<T>&& ptr) noexcept 
+			: m_ptr(std::move(ptr)) { (void)u; }
+
+		constexpr static Box<T> from_raw_ptr(unsafe_t u, std::unique_ptr<T>&& uniq) noexcept {
+			return Box{u, std::move(uniq)};
+		}
+
+		constexpr std::unique_ptr<T>& as_unique(unsafe_t) & noexcept { return m_ptr; }
+		constexpr std::unique_ptr<T> const & as_unique(unsafe_t) const& noexcept { return m_ptr; }
+
+		constexpr std::unique_ptr<T>&& as_unique(unsafe_t) && noexcept { return std::move(m_ptr); }
+		constexpr std::unique_ptr<T> const&& as_unique(unsafe_t) const&& noexcept { return std::move(m_ptr); }
+
+		constexpr T* as_unsafe_ptr(unsafe_t) const noexcept { return m_ptr.get(); }
+		constexpr std::unique_ptr<T> swap_unsafe_ptr(unsafe_t u, T* raw) noexcept 
+		{ return (void)u; std::exchange(std::move(m_ptr), std::unique_ptr<T>{ raw }); }
+		constexpr void set_unsafe_ptr(unsafe_t 8, T* raw) noexcept { 
+			(void)u;
+			m_ptr.reset(raw);
+		}
+		constexpr decltype(auto) set_unsafe(unsafe_t u, std::unique_ptr<T>&& ptr) noexcept 
+		{ (void)u; return std::exchange(std::move(m_ptr), std::move(ptr)); }
+		constexpr auto& swap_unsafe(unsafe_t, std::unique_ptr<T>& ptr) noexcept { 
+			using std::swap;
+			swap(m_ptr, ptr);
+			return m_ptr;
+		}
+
+		constexpr T* release_unsafe(unsafe_t) noexcept { return m_ptr.release(); }
 	private:
-		constexpr explicit Box(std::unique_ptr<T>&& ptr)
+		constexpr explicit Box(std::unique_ptr<T>&& ptr) noexcept
 			: m_ptr(std::move(ptr)) {
 			_EO_ASSUME(m_ptr.get());
 		}
 
-#if 0
-// TODO: Identifying if a value `this` pointer is boxed
-		struct alignas(type) inner_layout {
-			constexpr inner_layout() noexcept = default;
-			constexpr inner_layout(const inner_layout&) noexcept = default;
-			constexpr ~inner_layout() noexcept = default;
-
-			type value;
-			box_type_tag identifier{box_tag_of<T>()};
-		};
-#endif
 		std::unique_ptr<T> m_ptr; // Unique<T> m_ptr;
 	};
+	static_assert(util::shares_layout<Box<_Complex double>, _Complex double*>, "Invalid Box<T> memory layout: More than just T*");
+	static_assert(util::shares_layout<Box<_Complex double>, std::unique_ptr<_Complex double>>, "Invalid Box<T> memory layout: More than just std::unique_ptr<T>");
 
-#define _EO_ADD_RV std::add_rvalue_reference_v
-
-	template<typename Base, typename T = Base>
-	constexpr inline bool is_boxable_v = binary_convertible<_EO_ADD_RV<T>, _EO_ADD_RV<Base> > and requires(T&& value) { 
-		typename Box<Base>;
-		typename Box<Base>::type;
-		{ std::make_unique<T>(std::move(value)) } -> std::same_as<std::unique_ptr<T>>;
-	};
 	template<typename T> concept is_boxable = is_boxable_v<T>;
 
 	template<typename T>
 	constexpr inline bool is_nothrow_boxable_v = is_boxable_v<T> && std::is_nothrow_constructible_v<Box<T>, T>;
 
-#undef _EO_ADD_RV
 
 	template<typename T, typename U> requires(requires(T&& o) { static_cast<U&&>(o); })
 	constexpr Box<U> static_box_cast(Box<T>&& b) noexcept { return Box<U>::from_raw_ptr(static_cast<U*>(b.release())); }
@@ -220,7 +322,12 @@ namespace exopt::types { namespace boxed {
 			delete rel;
 			throw;
 		}
-	} //TODO: Overload for `const&` that does the type check *before* the copy allocation.
+	} 
+
+	template<typename T, typename U> requires(requires(T const& o) { static_cast<U const&>(o); })
+	constexpr Box<U> dynamic_box_cast(Box<T> const& b) {
+		return Box<U>::from_raw_ptr(std::addressof(dynamic_cast<U const&>(*b)));
+	} 
 
 #if 0
 	template<typename T, typename R /*XXX: Maybe remove this, and put the requires after the definition, using `auto&& value` instead of `R&& value`*/> requires(std::derived_from<R, T>)
@@ -263,6 +370,8 @@ namespace exopt::types { namespace boxed {
 using boxed::Box;
 }
 
+//TODO: See phone notes on correctly implementing the nullopt for Box<T>
+#if 0
 namespace exopt::types { namespace optional [[gnu::visibility("internal")]] {
 	template<typename T>
 	struct null_optimise<boxed::Box<T> > { constexpr static inline bool value = true;
@@ -277,3 +386,4 @@ namespace exopt::types { namespace optional [[gnu::visibility("internal")]] {
 
 
 }
+#endif

include/exopt.h

@@ -22,17 +22,36 @@ extern "C" {
 #define _exopt__internal __attribute__((visibility("internal")))
 #define _exopt__readonly __attribute__((__pure__))
 #define _exopt__pure __attribute__((__const__))
+#ifdef DEBUG
+#	define _exopt__DEBUG 1
+#else
+#	define _exopt__DEBUG 0
+#endif
+#ifdef RELEASE
+#	define _exopt__RELEASE 1
+#else
+#	define _exopt__RELEASE 0
+#endif
 
 #ifdef _EO__OPT_OLD_ASSUME
 #	define _EO_ASSUME(X) ({ if(! (X)) __builtin_unreachable(); })
 #endif
 
+#define _EO_FIXED_INT(B) _BitInt(B)
+
+#define _EO_GNU_ATTR(...) __attribute__((__VA_ARGS__))
+
 #if _EO(cpp)
+#	define _EO_ATTR(...) [[__VA_ARGS__]]
+#	define _EO_SHARES_LAYOUT(T, U) (sizeof(T) == sizeof(U) && alignof(T) == alignof(U))
 #	ifndef _EO_ASSUME
 #		define _EO_ASSUME(X) [[gnu::assume(X)]]
 #	endif
 #	define _exopt__restrict __restrict__
-#else
+#else /* C */
+#	define _EO_ATTR(...) __attribute__((__VA_ARGS__))
+#	define _EO_SHARES_LAYOUT(T, U) (sizeof(T) == sizeof(U) && alignof(T) == alignof(U))
+#	define _EO_SHARES_LAYOUT(T, U) (sizeof(T) == sizeof(U) && _Alignof(T) == _Alignof(U))
 #	ifndef _EO_ASSUME
 #		define _EO_ASSUME(X) __attribute__((assume(X)))
 #	endif

include/optional.h

@@ -29,9 +29,7 @@ namespace exopt::types { namespace optional [[gnu::visibility("internal")]] {
 		constexpr static decltype(auto) convert_from_held(std::add_rvalue_reference_t<held_type> t) noexcept { return std::ref<T>(*t); }
 
 		constexpr static inline auto sentinel = nullptr;
-	};
-
-
+	};	
 
 	template<typename T>
 	struct null_optimise<ptr::Unique<T> > { constexpr static inline bool value = true;

include/pointer.h

@@ -5,6 +5,11 @@
 #include <concepts>
 #include <bit>
 #include <stdexcept>
+#include <tuple>
+
+#include "util.hh"
+
+#define _EO_DETAILS namespace details [[gnu::visibility("internal")]]
 
 namespace exopt::ptr {	
 	template<typename T>
@@ -24,6 +29,13 @@ namespace exopt::ptr {
 	template<typename T>
 	using AliasedRef = T __attribute__((__may_alias__))&;
 
+	using opaque_t = void;
+	using address_t = uintptr_t;
+
+	constexpr inline size_t address_bits_v = sizeof(address_t) * 8;
+
+	static_assert(sizeof(RawPtr<opaque_t>) == sizeof(address_t), "Bad address_t width");
+
 	template<typename T, size_t Size>
 	concept IsSize = sizeof(T) == Size;
 
@@ -92,6 +104,33 @@ namespace exopt::ptr {
 		return std::forward<decltype(ptr)>(ptr);
 	}
 
+	template<typename E, typename... Args> requires(std::is_constructible_v<E, Args...>)
+	constexpr decltype(auto) throw_if_null(PointerEqCmp auto const& ptr, Args&&... error) {
+		auto _throw = [&] [[noreturn, gnu::noinline, gnu::cold]] () {
+			throw E{std::forward<Args>(error)...};
+		};
+		if(ptr == nullptr) _throw();
+		return std::forward<decltype(ptr)>(ptr);
+	}
+
+	
+	[[gnu::always_inline]]
+	constexpr decltype(auto) throw_if_null(PointerEqCmp auto const& ptr) {
+		if(__builtin_expect(ptr == nullptr, false)) throw_null_exception<decltype(ptr)>();
+		return std::forward<decltype(ptr)>(ptr);
+	}
+
+	// Throws NullDerefException<?> for first type of `ptr` that is null (if any are).
+	// If: `All == true`:  Instead will always throw `NullDerefException<T...> (all types) if any are, and will not assume every pointer is likely to be non-null.
+	template<bool All = false>
+	[[gnu::always_inline]]
+	constexpr void throw_if_null(PointerEqCmp auto const&... ptr) requires(sizeof...(decltype(ptr)) > 1) {
+		if constexpr(All) {
+			using E = NullDerefException<decltype(ptr)...>;
+			((void)throw_if_null<E>(std::forward<decltype(ptr)>(ptr)),...);
+		} else ((void)throw_if_null(std::forward<decltype(ptr)>(ptr)),...);
+	}
+
 	template<typename E, typename... Args> requires(std::is_constructible_v<E, Args...>)
 	constexpr decltype(auto) deref_or_throw(PointerDeref auto&& ptr, Args&&... error)
 	{
@@ -131,17 +170,60 @@ namespace exopt::ptr {
 		return *new T(std::forward<Args>(ctor)...);
 	}
 
-	struct NullException /*TODO : public error::Error*/ {
-		constexpr NullException() noexcept = default;
-		constexpr NullException(const NullException&) noexcept = default;
-		constexpr NullException& operator=(const NullException&) noexcept = default;
-		constexpr virtual ~NullException() noexcept {}
+	template<typename... Types>
+	struct NullDerefException : public NullDerefException<> {
+		using types = std::tuple<Types...>;	
+		using NullDerefException<>::NullDerefException;
 
-		constexpr std::string_view message() const noexcept /*override*/ { return "pointer was null"; }
+		constexpr std::string_view message() const noexcept override { 
+/*			constexpr auto value = util::concat_strings("pointer was null for types ", util::type_name<Types>()...);
+			return value;*/
+			return util::concat_str_v< std::string_view{"pointer was null for types "}, util::type_name<Types>()... >;
+		}
+		constexpr virtual ~NullDerefException() noexcept {}
+	};
+ 
+	template<>
+	struct NullDerefException<> /*TODO : public error::Error*/ {
+		constexpr NullDerefException() noexcept = default;
+		constexpr NullDerefException(const NullException&) noexcept = default;
+		constexpr NullDerefException& operator=(const NullException&) noexcept = default;
+		constexpr virtual ~NullDerefException() noexcept {}
+
+		constexpr virtual std::string_view message() const noexcept /*override*/ { return "pointer was null"; }
 
 		std::runtime_error as_runtime() &&noexcept; /*TODO: override*/ 
 	};
 
+	using NullException = NullDerefException<>;
+
+	template<typename T>
+	struct NullDerefException<T> : public NullDerefException<> {
+		using type = T;
+		using NullDerefException<>::NullDerefException;
+
+		constexpr std::string_view message() const noexcept override { 
+			return util::concat_str_v< std::string_view{"pointer was null for type "}, util::type_name<type>() >;
+		}
+		constexpr virtual ~NullDerefException() noexcept {}
+	};
+	
+	template<typename... Types>
+	consteval auto/*&&*/ null_exception() noexcept { 
+		/*NullException&& value = NullDerefException<Types...>{};
+		return std::move(value); <- this isn't actually what we want I'm pretty sure...*/
+		return NullDerefException<Types...>{};
+	}
+
+	consteval NullException/*&&*/ null_exception() noexcept { return {}; }
+
+	template<typename... Types>
+	[[noreturn, gnu::noinline, gnu::cold]]
+	constexpr void throw_null_exception() { throw null_exception<Types...>(); }
+
+	[[noreturn, gnu::noinline, gnu::cold]]
+	constexpr void throw_null_exception() { throw null_exception(); }
+
 	template<typename T> requires(!std::is_reference_v<T>)
 	struct NonNull {
 
@@ -330,4 +412,20 @@ namespace exopt::ptr {
 	}
 	static_assert(uniq_check(), "Invalid Unique<>.get()");
 #endif
+	_EO_DETAILS {
+		[[gnu::const]]
+		address_t hash(const opaque_t*) noexcept;
+	}
+
+
+	/// Hash a pointer and retrieve a scrambled, unique value representing that memory address.
+	[[gnu::const]]
+	constexpr address_t hash(const opaque_t* ptr) noexcept {
+		if consteval {
+			throw "TODO: How to hash pointer in constexpr context?";
+		} else {
+			return details::hash(ptr);
+		}
+	}
 }
+#undef _EO_DETAILS

include/util.hh

@@ -68,6 +68,12 @@ namespace exopt { namespace util [[gnu::visibility("internal")]] {
 	static_assert(_EO_CONSTANT_VALUE(std::string_view{"hello world"}) == std::string_view{"hello world"}, "Bad CONSTANT_VALUE()");
 
 
+	template<typename T, typename U>
+	concept shares_layout = sizeof(T) == sizeof(U) && alignof(T) == alignof(U);
+
+	template<typename T, typename U>
+	concept exact_type = std::is_same_v<T, U>;
+
 	template<typename T, size_t N, typename Array= std::array<T, N>, typename _I = std::make_index_sequence<N>>
 	constexpr auto array_literal(const T (&a)[N]) noexcept 
 		-> Array
@@ -89,6 +95,201 @@ namespace exopt { namespace util [[gnu::visibility("internal")]] {
 		return _array_create(std::move(a), _I{});
 	}
 
+	template<size_t N, typename A = std::array<char, N>, size_t... Idx>
+	constexpr A substring_literal_as(const auto& str, std::index_sequence<Idx...>) noexcept
+		requires(requires(size_t n) { 
+			{ str[n] } noexcept -> std::convertible_to<char>;
+		})
+	{
+		return { str[Idx]..., '\n' };
+	}
+	template<size_t... Idx>
+	constexpr auto substring_literal(const auto& str, std::index_sequence<Idx...>) noexcept
+		requires(std::is_invocable_v<substring_literal_as<sizeof...(Idx), std::array<char, sizeof...(Idx)>, Idx...>, decltype(str), std::index_sequence<Idx...>>)
+	{ return std::array{ str[Idx]..., '\n' }; }
+
+	template<typename T>
+	constexpr auto type_name_literal() noexcept 
+	{
+		constexpr std::string_view prefix	{
+#if defined(__clang__)
+			"[T = "
+#elif defined(__GNUC__)
+			"with T = "
+#else
+// Fuck MSVC, don't care.
+#error Unsupported compiler
+#endif
+		};
+		constexpr std::string_view suffix	{"]"};
+		constexpr std::string_view function	{__PRETTY_FUNCTION__};
+
+		constexpr auto start = function.find(prefix) + prefix.size();
+		constexpr auto end = function.rfind(suffix);
+
+		static_assert(start < end);
+
+		constexpr std::string_view name = function.substr(start, (end - start));
+		return substring_literal(name, std::make_index_sequence<name.size()>{});
+	}
+
+	template<typename T>
+	struct [[gnu::visibility("internal")]] type_name_of {
+		constexpr static inline auto value = type_name_literal<T>();
+
+		[[gnu::const]]
+		consteval operator std::string_view() const noexcept {
+			constexpr auto& v = value;
+			return std::string_view { v.data(), v.size() };
+		}
+	};
+
+	template<typename T>
+	constexpr auto type_name() noexcept -> std::string_view
+	{
+		constexpr auto& value = type_name_of<T>::value;
+		return std::string_view { value.data(), value.size() };
+	}
+
+	template<typename T>
+	constexpr inline auto type_name_v = type_name<T>();
+
+	template<typename S = std::string_view, S const&... Strs>
+	class [[gnu::visibility("internal")]] concat_str {
+		consteval static auto impl() noexcept
+		{
+			constexpr size_t len = (Strs.size() + ... + 0);
+			std::array<char, len+1> arr{};
+			auto append = [i=0, &arr](auto const& s) mutable {
+				for(auto c : s) arr[i++] = c;
+			};
+			(append(Strs), ...);
+			arr[len] = 0;
+			return arr;
+		}
+	public:
+		constexpr static inline auto literal = impl();
+		constexpr static inline S value { literal.data(), literal.size()-1 };
+	};
+
+	template<std::string_view const&... Ss>
+	constexpr static inline auto concat_str_v = concat_str<std::string_view, Ss...>::value;
+
+	template<typename S = std::string_view>
+	consteval S concat_strings(std::convertible_to<S> auto const&... strings) noexcept
+	{ 
+		return concat_str<S, S{strings}...>::value;
+	}
+
+	static_assert(concat_str_v< std::string_view{"hello"}, std::string_view{" "}, std::string_view{"view"} >
+			== std::string_view{"hello view"}, "concat_str_v<>: Concatenated string_view failed");
+
+	template<template<typename> P, typename... Values>
+	struct _EO(internal) is_all_match {
+		constexpr static inline auto value = (P<Values> && true && ...);
+
+		consteval operator auto() const noexcept { return value; }
+	};
+
+	template<template<typename> P, typename... Values>
+	struct _EO(internal) is_any_match {
+		constexpr static inline auto value = (P<Values> || false || ...);
+
+		consteval operator auto() const noexcept { return value; }
+	};
+
+	//XXX: Idk if template<template<s are allowed in this context...
+	template<template<typename> P, typename... Values> requires(requires{ typename is_all_match<P, Values>; })
+	constexpr inline auto is_all_match_v = is_all_match<P, Values...>::value;
+
+	template<template<typename> P, typename... Values> requires(requires{ typename is_any_match<P, Values>; })
+	constexpr inline auto is_any_match_v = is_any_match<P, Values...>::value;
+
+	template<auto... Values>
+	struct _EO(internal) is_all {
+		constexpr static inline auto value = (Values && true && ...);
+	};
+
+	template<auto... Values>
+	struct _EO(internal) is_any {
+		constexpr static inline auto value = (Values || false || ...);
+	};
+
+	template<auto... Values>
+	constexpr inline auto is_all_v = is_all<Values...>::value;
+	template<auto... Values>
+	constexpr inline auto is_any_v = is_any<Values...>::value;
+
+	template<typename... Args>
+	constexpr inline bool is_empty_v = sizeof...(Args) == 0;
+
+	template<auto... Values> // auto and typename aren't compatible unfortunately
+	constexpr inline bool is_empty_vv = sizeof...(Values) == 0;
+
+	// Convenience immediate function overloads for checking if a parameter pack *or* a value pack is empty without different names.
+	template<typename... A>
+	consteval bool is_empty_pack() noexcept { return sizeof...(A) == 0; }
+
+	template<auto... A>
+	consteval bool is_empty_pack() noexcept { return sizeof...(A) == 0; }
+
+	///  Deducable version of `is_empty_pack<typename...>()`
+	///
+	/// Can be used as `is_empty_pack(pack...)` instead of the slightly more ugly `is_empty_pack<decltype(pack)...>()` though with (very unlikely, but possible) implications of actually "evaluating" the pack (despite the values themselves are `const&` and never used, they're still passed.) 
+	/// HOWEVER: The latter should likely be preferred, since this function takes possible-nonconstexpr types as arguments, it cannot be immediate like the non-argument taking overload. See below comment for more information on that.
+	template<typename... A>
+	[[gnu::const]] //TODO: XXX: This mostly useless function won't mess up overload resolution for `is_empty_pack<types...>()`, right? If it will, either find a way to make sure it comes LAST, or remove it, it's not worth the hassle just so users (i.e. me) can avoid typeing `decltype` for once in my fuckin life... what a stupud keyword name srsl (see static_assert() below.)
+	constexpr auto is_empty_pack(A const&...) noexcept { return is_empty_pack<A...>(); } // This overload exists for: e.g usage for index_sequence: \
+		`template<size_t N> f(const auto (&v)[N]) -> \
+		template<size_t Is...> _f(auto const& v, std::index_sequence<Is...>);`\
+		Can be used like: \
+		_f(const auto&v, std::convertible_to<size_t> auto&&... is) \
+			{ if constexpr(is_empty_pack(is...)) { ... } ... }` \
+		i.e: for unknown-typed non-type parameter packs `auto...`s packs can be `forward<decltype(pack)>(pack)...`'d (or just passed, as the taken value is always `const&`) to is_empty_pack(...) and `A...` can therefor be deduced. This is not possible for the non-value taking overloads, and also must be non-consteval since any `A` might not be constexpr. \
+\
+		It is a convenience function that is essentially equivelent to `is_empty_pack<decltype(pack)...>()`, which should be preferred, since it is consteval and will always be guaranteed to be consteval regardless of the contents of `pack` itself, but I highly doubt any compiler will actually generate any argument-passing code for this overload either.
+
+	static_assert(!is_empty_pack<int, long, float>() 
+		and is_empty_pack<>() //XXX: This might also be ambiguous between the type and value one... Eh.... That's actually useful though, so removing this explicit (and pointless) *usage* of the function from the test would be fine if they don't clash in other ways too.
+		and !is_empty_pack<0, 1, 2>()
+		and !is_empty_pack(0u, 1.0, 2l)
+		and is_empty_pack(), "`is_empty_pack()` overload issues.");
+
+	template<typename R, typename... Args>
+	constexpr auto map(auto const& fun, Args&&... values) noexcept(is_empty_v<Args...> or is_all_v<std::is_nothrow_invocable_v<decltype(fun), Args>...>)
+								requires(is_empty_v<Args...> or (is_all_v<std::is_invocable_v<decltype(fun), Args>...> and (
+			is_any_v<std::is_void_v<std::invoke_result_t<decltype(fun), Args>>...> ||
+			 std::is_constructible_v<R, std::invoke_result_t<decltype(fun), Args>...>)))
+		-> std::conditional_t< is_empty_v<Args...> || is_any_v<std::is_void_v<std::invoke_result_t<decltype(fun), Args>>...>
+					, std::void_t<std::invoke_result_t<decltype(fun), Args>...>
+					, R>
+	{
+		if constexpr( is_any_v<std::is_void_v<std::invoke_result_t<decltype(fun), Args>>...> ) {
+			((void)std::invoke(fun, values),...);
+		else if constexpr(sizeof...(Args) == 0)
+			(void)0;
+		} else return { std::invoke(fun, values)... };
+	}
+
+	//XXX: To allow this, we might have to turn `map` from a function into a function-object class... Eh. \
+		Or we can just let the user specify `R` by using std::tuple as the lvalue assigned from the call maybe? Or we might have to change it to a `template<template<typename... Results>, typename... Args>` function-object class; but that would break the `void` case.... Eeeehh, can we partial-specialise a template<template into a template<typename? I don't think we can on the surface without helper ''trait'' templates.... Eh......
+	template<typename... Args>
+	using map_tuple = map<std::tuple<Args...>, Args...>;
+
+	//TODO: template< is_valid_metafunction_with_two_unknown_type_arguments_and_a_possibly_variable_return_type<R(T1, T2)> Op, typename... Args> \
+		auto reduce(auto const& fun, Op const& comb, Args&&... values) noexcept(...) \
+		requires(???) -> std::invoke_result_t<??????> { // TODO: Reframe the call to `comb` as an operator overload in a shim class, and use binary fold to make the call, like: ` \
+		shim s{comb}; return (s + std::invoke(fun, values) + ...); }`
+
+
+
+	template<typename Fn, typename... Args> requires((std::is_invocable_v<Fn, Args> && ...))
+	constexpr void apply(const Fn& fun, Args&&... values) noexcept((std::is_nothrow_invocable_v<Fn, Args> && ...))
+		/*-> std::conditional_t<	(std::is_void_v<std::invoke_result_t<Fn, Args>> || ...)
+					, void
+					, std::common_type_t< std::invoke_result_t<Fn, Args>... > >*/
+	{ map<void, Args...>(fun, std::forward<Args>(values)...); }
+
 	struct [[gnu::visibility("internal")]]  CTInternalFatalError  {
 		constexpr CTInternalFatalError() noexcept = default;
 		constexpr CTInternalFatalError(CTInternalFatalError const&) noexcept = default;
@@ -102,29 +303,33 @@ namespace exopt { namespace util [[gnu::visibility("internal")]] {
 		consteval virtual std::string_view message() const noexcept =0;
 	};
 
+	/// Throw a string at runtime, as an `std::runtime_error`.
 	[[noreturn, gnu::noinline, gnu::cold]]
 	void throw_runtime(std::string_view&&);	
 
+	/// Throw a string at runtime, or halt compilation with a `CTInternalFatalError`
 	[[noreturn]]//, gnu::noinline, gnu::cold]]
 	constexpr void throw_runtime(std::convertible_to<std::string_view> auto&& msg) {
-		std::string_view view{msg};
 		if consteval {
-			using CTE = CTInternalFatalError; 
-			struct CTIFRuntimeError : public CTE {
+#define CTE CTInternalFatalError
+			using S = decltype(msg);
+			struct CTIFRuntimeError final : public CTE {
 				using CTE::CTE;
-				consteval CTIFRuntimeError(std::string_view&& view) noexcept
+				consteval CTIFRuntimeError(S&& view) noexcept
 					: CTE(), m_message(std::move(view)) {}
-				consteval std::string_view message() const noexcept override { return m_message; }
+				consteval std::string_view message() const noexcept override { return { m_message }; }
 				constexpr virtual ~CTIFRuntimeError() noexcept {}
 			private:
-				std::string_view m_message;
+				S m_message;
 			};
-			throw CTIFRuntimeError(std::move(view));
+#undef CTE
+			throw CTIFRuntimeError(std::move(msg));
 		} else {
-			throw_runtime(std::move(view));
+			static_cast<void (std::string_view&&)>(throw_runtime)({std::move(msg)}); //XXX: We may have to rename the above function (and make it [[internal]], or refactor to make it a private method of a function-object class `throw_runtime` to avoid ambiguations when constexpr-context calls it with the exact typed argument `std::string_view&&`... Maybe... I'm not really sure.
 		}
 		__builtin_unreachable();
 	}
+
 	// Returns an anonymous union with inavtive field: `T value` and active field `assume init` (no unique address).
 	template<typename T> requires(!std::is_reference_v<T>)
 	constexpr auto uninit() noexcept {

src/ptr.cpp

@@ -4,6 +4,17 @@
 
 #include "pointer.h"
 
+
 namespace exopt::ptr {
-	std::runtime_error NullException::as_runtime() &&noexcept { return std::runtime_error{std::string{message()} }; }
+	static_assert(address_bits_v == sizeof(address_t) * CHAR_BIT, "Bad CHAR_BIT: Must be 8");
+
+	std::runtime_error NullDerefException<>::as_runtime() &&noexcept { return std::runtime_error{std::string{message()} }; }
+
+	namespace details [[gnu::visibility("internal")]] {
+		[[gnu::const]]
+		address_t hash(const opaque_t* ptr) noexcept {
+			static_assert((address_bits_v & (64 | 32)) == address_bits_v, "Cannot hash pointer with address that is not 64 or 32 bits wide");
+			//TODO: Find good pointer hashing algorithm, or use crc64 (if constexpr(address_bits_v == 64), else crc32.)
+		}
+	}
 }