378 lines
15 KiB
C
378 lines
15 KiB
C
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#pragma once
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/*
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* Created by Brett on 06/02/24.
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* Licensed under GNU General Public License V3.0
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* See LICENSE file for license detail
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*/
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#ifndef BLT_EXPECTED_H
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#define BLT_EXPECTED_H
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#include <blt/compatibility.h>
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#include <variant>
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#include <type_traits>
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#include <utility>
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namespace blt
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{
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struct unexpect_t
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{
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explicit unexpect_t() = default;
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};
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inline constexpr unexpect_t unexpect{};
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template<typename T>
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using remove_cvref_t = std::remove_reference_t<std::remove_cv_t<T>>;
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template<class E>
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class unexpected
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{
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private:
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E e;
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public:
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constexpr unexpected(const unexpected&) = default;
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constexpr unexpected(unexpected&&) = default;
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template<class Err = E, std::enable_if_t<
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!std::is_same_v<remove_cvref_t<Err>, unexpected> && !std::is_same_v<remove_cvref_t<Err>, std::in_place_t> &&
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std::is_constructible_v<E, Err>, bool> = true>
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constexpr explicit unexpected(Err&& e): e(std::forward<Err>(e))
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{}
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template<class... Args, std::enable_if_t<std::is_constructible_v<E, Args...>, bool> = true>
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constexpr explicit unexpected(std::in_place_t, Args&& ... args): e(std::forward<Args>(args)...)
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{}
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template<class U, class... Args, std::enable_if_t<std::is_constructible_v<E, std::initializer_list<U>&, Args...>, bool> = true>
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constexpr explicit unexpected(std::in_place_t, std::initializer_list<U> il, Args&& ... args): e(il, std::forward<Args>(args)...)
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{}
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constexpr const E& error() const& noexcept
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{
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return e;
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}
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constexpr E& error()& noexcept
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{
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return e;
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}
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constexpr const E&& error() const&& noexcept
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{
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return e;
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}
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constexpr E&& error()&& noexcept
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{
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return e;
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}
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constexpr void swap(unexpected& other) noexcept(std::is_nothrow_swappable_v<E>)
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{
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std::swap(error(), other.error());
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}
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template<typename E2>
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inline friend constexpr bool operator==(const unexpected& x, const unexpected <E2>& y)
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{
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return x.error() == y.error();
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}
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friend constexpr void swap(unexpected& x, unexpected& y) noexcept(noexcept(x.swap(y)))
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{}
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};
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template<class E>
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unexpected(E) -> unexpected<E>;
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template<class E>
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class bad_expected_access : public std::exception
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{
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private:
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E e;
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public:
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explicit bad_expected_access(E e): e(std::move(e))
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{}
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const E& error() const& noexcept
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{ return e; }
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E& error()& noexcept
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{ return e; }
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const E&& error() const&& noexcept
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{ return e; }
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E&& error()&& noexcept
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{ return e; }
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[[nodiscard]] const char* what() const noexcept override
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{ return "blt::expected does not contain a value!"; }
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};
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template<typename T, typename E, bool = std::is_copy_constructible_v<T>>
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class expected
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{
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protected:
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std::variant<T, E> v;
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template<typename U, typename G>
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inline static constexpr bool eight_insanity_v =
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std::is_constructible_v<T, expected<U, G>&> || std::is_constructible_v<T, expected<U, G>> ||
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std::is_constructible_v<T, const expected<U, G>&> || std::is_constructible_v<T, const expected<U, G>> ||
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std::is_convertible_v<expected<U, G>&, T> || std::is_convertible_v<expected<U, G>, T> ||
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std::is_convertible_v<const expected<U, G>&, T> || std::is_convertible_v<const expected<U, G>, T>;
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template<typename U, typename G>
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inline static constexpr bool four_insanity_v =
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std::is_constructible_v<unexpected<E>, expected<U, G>&> || std::is_constructible_v<unexpected<E>, expected<U, G>> ||
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std::is_constructible_v<unexpected<E>, const expected<U, G>&> || std::is_constructible_v<unexpected<E>, const expected<U, G>>;
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public:
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template<typename std::enable_if_t<std::is_default_constructible_v<T>, bool> = true>
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constexpr expected() noexcept: v(T())
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{}
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constexpr expected(const expected& copy) = delete;
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constexpr expected(expected&& move) noexcept: v(move ? std::move(*move) : std::move(move.error()))
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{}
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/*
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* (4)...(5)
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*/
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template<class U, class G, class UF = std::add_lvalue_reference_t<const U>, class GF = const G&, std::enable_if_t<
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(!std::is_convertible_v<UF, T> || !std::is_convertible_v<GF, E>) && (std::is_constructible_v<T, UF> || std::is_void_v<U>) &&
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std::is_constructible_v<E, GF> && !eight_insanity_v < U, G>&& !four_insanity_v<U, G>, bool> = true>
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constexpr explicit expected(const expected<U, G>& other):
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v(other.has_value() ? std::forward<UF>(*other) : std::forward<GF>(other.error()))
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{}
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template<class U, class G, class UF = U, class GF = G, std::enable_if_t<
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(!std::is_convertible_v<UF, T> || !std::is_convertible_v<GF, E>) && (std::is_constructible_v<T, UF> || std::is_void_v<U>) &&
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std::is_constructible_v<E, GF> && !eight_insanity_v < U, G>&& !four_insanity_v<U, G>, bool> = true>
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constexpr explicit expected(expected<U, G>&& other):
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v(other.has_value() ? std::forward<UF>(*other) : std::forward<GF>(other.error()))
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{}
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template<class U, class G, class UF = std::add_lvalue_reference_t<const U>, class GF = const G&, std::enable_if_t<
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(std::is_convertible_v<UF, T> && std::is_convertible_v<GF, E>) && (std::is_constructible_v<T, UF> || std::is_void_v<U>) &&
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std::is_constructible_v<E, GF> && !eight_insanity_v < U, G>&& !four_insanity_v<U, G>, bool> = true>
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constexpr expected(const expected<U, G>& other):
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v(other.has_value() ? std::forward<UF>(*other) : std::forward<GF>(other.error()))
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{}
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template<class U, class G, class UF = U, class GF = G, std::enable_if_t<
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(std::is_convertible_v<UF, T> && std::is_convertible_v<GF, E>) && (std::is_constructible_v<T, UF> || std::is_void_v<U>) &&
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std::is_constructible_v<E, GF> && !eight_insanity_v < U, G>&& !four_insanity_v<U, G>, bool> = true>
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constexpr expected(expected<U, G>&& other):
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v(other.has_value() ? std::forward<UF>(*other) : std::forward<GF>(other.error()))
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{}
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/*
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* (6)
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*/
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template<class U = T, std::enable_if_t<!std::is_convertible_v<U, T> &&
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!std::is_same_v<remove_cvref_t<T>, void> &&
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!std::is_same_v<remove_cvref_t<U>, std::in_place_t> &&
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!std::is_same_v<expected, remove_cvref_t<U>> &&
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std::is_constructible_v<T, U> &&
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!std::is_same_v<remove_cvref_t<U>, unexpected<U>> &&
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!std::is_same_v<remove_cvref_t<U>, expected<T, E>>, bool> = true>
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constexpr explicit expected(U&& v): v(T(std::forward<U>(v)))
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{}
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template<class U = T, std::enable_if_t<std::is_convertible_v<U, T> &&
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!std::is_same_v<remove_cvref_t<T>, void> &&
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!std::is_same_v<remove_cvref_t<U>, std::in_place_t> &&
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!std::is_same_v<expected, remove_cvref_t<U>> &&
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std::is_constructible_v<T, U> &&
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!std::is_same_v<remove_cvref_t<U>, unexpected<U>> &&
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!std::is_same_v<remove_cvref_t<U>, expected<T, E>>, bool> = true>
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constexpr expected(U&& v): v(T(std::forward<U>(v)))
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{}
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/*
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* (7)
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*/
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template<class G, class GF = std::add_const_t<std::add_lvalue_reference_t<G>>, std::enable_if_t<
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!std::is_convertible_v<const G&, E> && std::is_constructible_v<E, GF>, bool> = true>
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constexpr explicit expected(const unexpected<G>& e): v(std::forward<GF>(e.error()))
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{}
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template<class G, class GF = std::add_const_t<std::add_lvalue_reference_t<G>>, std::enable_if_t<
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std::is_convertible_v<const G&, E> && std::is_constructible_v<E, GF>, bool> = true>
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constexpr expected(const unexpected<G>& e): v(std::forward<GF>(e.error()))
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{}
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/*
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* (8)
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*/
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template<class G, class GF = std::add_const_t<std::add_lvalue_reference_t<G>>, std::enable_if_t<
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!std::is_convertible_v<G, E> && std::is_constructible_v<E, GF>, bool> = true>
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constexpr explicit expected(unexpected<G>&& e): v(std::forward<GF>(e.error()))
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{}
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template<class G, class GF = std::add_const_t<std::add_lvalue_reference_t<G>>, std::enable_if_t<
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std::is_convertible_v<G, E> && std::is_constructible_v<E, GF>, bool> = true>
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constexpr expected(unexpected<G>&& e): v(std::forward<GF>(e.error()))
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{}
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/*
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* (9)...(13)
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*/
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template<class... Args, std::enable_if_t<std::is_constructible_v<T, Args...>, bool> = true>
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constexpr explicit expected(std::in_place_t, Args&& ... args): v(T(std::forward<Args>(args)...))
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{}
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template<class U, class... Args, std::enable_if_t<std::is_constructible_v<T, std::initializer_list<U>&, Args...>, bool> = true>
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constexpr explicit expected(std::in_place_t, std::initializer_list<U> il, Args&& ... args): v(T(il, std::forward<Args>(args)...))
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{}
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// template<class... Args, std::enable_if_t<std::is_same_v<remove_cvref_t<T>, void>, bool> = true>
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// constexpr explicit expected(std::in_place_t) noexcept: v(T())
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// {}
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template<class... Args, std::enable_if_t<std::is_constructible_v<E, Args...>, bool> = true>
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constexpr explicit expected(unexpect_t, Args&& ... args): v(E(std::forward<Args>(args)...))
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{}
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template<class U, class... Args, std::enable_if_t<std::is_constructible_v<E, std::initializer_list<U>&, Args...>, bool> = true>
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constexpr explicit expected(unexpect_t, std::initializer_list<U> il, Args&& ... args): v(E(il, std::forward<Args>(args)...))
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{}
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expected& operator=(const expected& copy) = delete;
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expected& operator=(expected&& move) = default;
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[[nodiscard]] constexpr explicit operator bool() const noexcept
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{
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return std::holds_alternative<T>(v);
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}
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[[nodiscard]] constexpr inline bool has_value() const noexcept
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{
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return std::holds_alternative<T>(v);
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}
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constexpr T& value()&
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{
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if (*this)
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return std::get<T>(v);
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else
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throw bad_expected_access(std::as_const(error()));
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}
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constexpr const T& value() const&
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{
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if (*this)
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return std::get<T>(v);
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else
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throw bad_expected_access(std::as_const(error()));
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}
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constexpr T&& value()&&
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{
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if (*this)
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return std::get<T>(v);
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else
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throw bad_expected_access(std::move(error()));
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}
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constexpr const T&& value() const&&
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{
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if (*this)
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return std::get<T>(v);
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else
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throw bad_expected_access(std::move(error()));
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}
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constexpr const E& error() const& noexcept
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{
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return std::get<E>(v);
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}
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constexpr E& error()& noexcept
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{
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return std::get<E>(v);
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}
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constexpr const E&& error() const&& noexcept
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{
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return std::get<E>(v);
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}
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constexpr E&& error()&& noexcept
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{
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return std::get<E>(v);
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}
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template<class U, std::enable_if_t<std::is_convertible_v<U, T> && std::is_copy_constructible_v<T>, bool> = true>
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constexpr T value_or(U&& default_value) const&
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{
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return bool(*this) ? **this : static_cast<T>(std::forward<U>(default_value));
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}
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template<class U, std::enable_if_t<std::is_convertible_v<U, T> && std::is_move_constructible_v<T>, bool> = true>
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constexpr T value_or(U&& default_value)&&
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{
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return bool(*this) ? std::move(**this) : static_cast<T>(std::forward<U>(default_value));
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}
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constexpr inline const T* operator->() const noexcept
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{
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return &std::get<T>(v);
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}
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constexpr inline T* operator->() noexcept
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{
|
||
|
|
return &std::get<T>(v);
|
||
|
|
}
|
||
|
|
|
||
|
|
constexpr inline const T& operator*() const& noexcept
|
||
|
|
{
|
||
|
|
return std::get<T>(v);
|
||
|
|
}
|
||
|
|
|
||
|
|
constexpr inline T& operator*()& noexcept
|
||
|
|
{
|
||
|
|
return std::get<T>(v);
|
||
|
|
}
|
||
|
|
|
||
|
|
constexpr inline const T&& operator*() const&& noexcept
|
||
|
|
{
|
||
|
|
return std::move(std::get<T>(v));
|
||
|
|
}
|
||
|
|
|
||
|
|
constexpr inline T&& operator*()&& noexcept
|
||
|
|
{
|
||
|
|
return std::move(std::get<T>(v));
|
||
|
|
}
|
||
|
|
};
|
||
|
|
|
||
|
|
template<typename T, typename E>
|
||
|
|
class expected<T, E, true> : expected<T, E, false>
|
||
|
|
{
|
||
|
|
public:
|
||
|
|
using expected<T, E, false>::expected;
|
||
|
|
|
||
|
|
constexpr expected(const expected& copy): expected<T, E, false>::v(copy ? *copy : copy.error())
|
||
|
|
{}
|
||
|
|
|
||
|
|
expected& operator=(const expected& copy) = default;
|
||
|
|
};
|
||
|
|
}
|
||
|
|
|
||
|
|
#endif //BLT_EXPECTED_H
|