Home - News ( United States | United Kingdom | Italy | Germany ) - Football scores

Showing content from https://cplusplus.github.io/LWG/issue3938 below:

expected monadic ops with move-only error_type

For each Effects: element in 22.8.6.7 [expected.object.monadic], replace value() with **this as indicated:

template<class F> constexpr auto and_then(F&& f) &;
template<class F> constexpr auto and_then(F&& f) const &;

-1- Let U be remove_cvref_t<invoke_result_t<F, decltype( value() **this)>>.

-2- Constraints: is_constructible_v<E, decltype(error())> is true.

-3- Mandates: U is a specialization of expected and is_same_v<U::error_type, E> is true.

-4- Effects: Equivalent to:

if (has_value())
  return invoke(std::forward<F>(f), value()**this);
else
  return U(unexpect, error());

template<class F> constexpr auto and_then(F&& f) &&;
template<class F> constexpr auto and_then(F&& f) const &&;

-5- Let U be remove_cvref_t<invoke_result_t<F, decltype(std::move( value() **this))>>.

-6- Constraints: is_constructible_v<E, decltype(std::move(error()))> is true.

-7- Mandates: U is a specialization of expected and is_same_v<U::error_type, E> is true.

-8- Effects: Equivalent to:

if (has_value())
  return invoke(std::forward<F>(f), std::move(value()**this));
else
  return U(unexpect, std::move(error()));

template<class F> constexpr auto or_else(F&& f) &;
template<class F> constexpr auto or_else(F&& f) const &;

-9- Let G be remove_cvref_t<invoke_result_t<F, decltype(error())>>.

-10- Constraints: is_constructible_v<T, decltype( value() **this)> is true.

-11- Mandates: G is a specialization of expected and is_same_v<G::value_type, T> is true.

-12- Effects: Equivalent to:

if (has_value())
  return G(in_place, value()**this);
else
  return invoke(std::forward<F>(f), error());

template<class F> constexpr auto or_else(F&& f) &&;
template<class F> constexpr auto or_else(F&& f) const &&;

-13- Let G be remove_cvref_t<invoke_result_t<F, decltype(std::move(error()))>>.

-14- Constraints: is_constructible_v<T, decltype(std::move( value() **this))> is true.

-15- Mandates: G is a specialization of expected and is_same_v<G::value_type, T> is true.

-16- Effects: Equivalent to:

if (has_value())
  return G(in_place, std::move(value()**this));
else
  return invoke(std::forward<F>(f), std::move(error()));

template<class F> constexpr auto transform(F&& f) &;
template<class F> constexpr auto transform(F&& f) const &;

-17- Let U be remove_cv_t<invoke_result_t<F, decltype( value() **this)>>.

-18- Constraints: is_constructible_v<E, decltype(error())> is true.

-19- Mandates: U is a valid value type for expected. If is_void_v<U> is false, the declaration

  U u(invoke(std::forward<F>(f), value()**this));

-20- Effects:

1. (20.1) — If has_value() is false, returns expected<U, E>(unexpect, error()).
2. (20.2) — Otherwise, if is_void_v<U> is false, returns an expected<U, E> object whose has_val member is true and val member is direct-non-list-initialized with invoke(std::forward<F>(f), value() **this).
3. (20.3) — Otherwise, evaluates invoke(std::forward<F>(f), value() **this) and then returns expected<U, E>().

template<class F> constexpr auto transform(F&& f) &&;
template<class F> constexpr auto transform(F&& f) const &&;

-21- Let U be remove_cv_t<invoke_result_t<F, decltype(std::move( value() **this))>>.

-22- Constraints: is_constructible_v<E, decltype(std::move(error()))> is true.

-23- Mandates: U is a valid value type for expected. If is_void_v<U> is false, the declaration

  U u(invoke(std::forward<F>(f), std::move(value()**this)));

[Drafting Note: The removal of "for some invented variable u" in paragraph 23 is a drive-by fix for consistency with paragraphs 19, 27 and 31.]

-24- Effects:

1. (24.1) — If has_value() is false, returns expected<U, E>(unexpect, error()).
2. (24.2) — Otherwise, if is_void_v<U> is false, returns an expected<U, E> object whose has_val member is true and val member is direct-non-list-initialized with invoke(std::forward<F>(f), std::move( value() **this)).
3. (24.3) — Otherwise, evaluates invoke(std::forward<F>(f), std::move( value() **this)) and then returns expected<U, E>().

template<class F> constexpr auto transform_error(F&& f) &;
template<class F> constexpr auto transform_error(F&& f) const &;

-25- Let G be remove_cv_t<invoke_result_t<F, decltype(error())>>.

-26- Constraints: is_constructible_v<T, decltype( value() **this)> is true.

-27- Mandates: G is a valie template argument for unexpected ( [unexpected.un.general]) and the declaration

  G g(invoke(std::forward<F>(f), error()));

-28- Returns: If has_value() is true, expected<T, G>(in_place, value() **this);; otherwise, an expected<T, G> object whose has_val member is false and unex member is direct-non-list-initialized with invoke(std::forward<F>(f), error()).

template<class F> constexpr auto transform_error(F&& f) &&;
template<class F> constexpr auto transform_error(F&& f) const &&;

-29- Let G be remove_cv_t<invoke_result_t<F, decltype(std::move(error()))>>.

-30- Constraints: is_constructible_v<T, decltype(std::move( value() **this))> is true.

-31- Mandates: G is a valie template argument for unexpected ( [unexpected.un.general]) and the declaration

  G g(invoke(std::forward<F>(f), std::move(error())));

-32- Returns: If has_value() is true, expected<T, G>(in_place, std::move( value() **this));; otherwise, an expected<T, G> object whose has_val member is false and unex member is direct-non-list-initialized with invoke(std::forward<F>(f), std::move(error())).

RetroSearch is an open source project built by @garambo | Open a GitHub Issue

Search and Browse the WWW like it's 1997 | Search results from DuckDuckGo

HTML: 3.2 | Encoding: UTF-8 | Version: 0.7.4