A class to represent the result of an operation which might fail. More...

#include <failable.hpp>

Inherits resilient::detail::Variant< Types >.

Public Types
using	failure_type = Failure
	Alias for the type of the failure.

using	value_type = Value
	Alias for the type of the value.

Public Member Functions
template<typename Other , if_is_failable< Other > = nullptr>
	Failable (Other &&other)
	Create a `Failable` from another `Failable`. More...

template<typename Other , if_is_not_failable< Other > = nullptr>
	Failable (Other &&other)
	Create a `Failable` from a either a `Failure` or a `Value`. More...

template<typename Other , if_is_failable< Other > = nullptr>
Failable &	operator= (Other &&other)
	Assign the value of another `Failable` to this `Failable`. More...

template<typename Other , if_is_not_failable< Other > = nullptr>
Failable &	operator= (Other &&other)
	Assign an object to this `Failable`. More...

Friends
template<typename Failable >
struct	detail::as_variant

template<typename Failable_ >
detail::as_variant_t< Failable_ >	detail::get_variant (Failable_ &&f)

Related Functions
(Note that these are not member functions.)
template<typename Value , typename Failure >
bool	holds_failure (const Failable< Value, Failure > &failable)
	Check whether the `Failable` contains a failure. More...

template<typename Value , typename Failure >
bool	holds_value (const Failable< Value, Failure > &failable)
	Check whether the `Failable` contains a value. More...

template<typename Failable , if_is_failable< Failable > = nullptr>
auto	get_failure (Failable &&failable) -> detail::same_const_ref_as_t< Failable, detail::failable_failure_type_t< Failable >>
	Get the failure in the `Failable`. More...

template<typename Failable , if_is_failable< Failable > = nullptr>
auto	get_value (Failable &&failable) -> detail::same_const_ref_as_t< Failable, detail::failable_value_type_t< Failable >>
	Get the value in the `Failable`. More...

template<typename Failable , if_is_failable< Failable > = nullptr>
auto	get_value_or (Failable &&failable, detail::get_value_return_type< Failable > default_value) -> detail::get_value_return_type< Failable >
	Get the value in the `Failable` or default_value if not present. More...

template<typename Failable , typename OtherFailable , if_is_failable< Failable > = nullptr, if_is_failable< OtherFailable > = nullptr>
auto	get_value_or (Failable &&failable, OtherFailable &&other) -> std::remove_const_t< std::remove_reference_t< OtherFailable >>
	Get the combination of two `Failable`s sharing the same value_type. More...

template<typename Failable , typename Invocable , typename InvocableResult = detail::invoke_result_t<Invocable>, if_is_failable< Failable > = nullptr, detail::if_is_convertible_to_get_value_return_type_of< Failable, InvocableResult > = nullptr>
auto	get_value_or_invoke (Failable &&failable, Invocable &&invocable) -> detail::get_value_return_type< Failable >
	Get the value in failable if it holds a value, the returned value of invoking `invocable` otherwise. More...

template<typename Failable , typename Invocable , typename InvocableResult = detail::invoke_result_t<Invocable>, if_is_failable< Failable > = nullptr, if_is_failable< InvocableResult > = nullptr>
auto	get_value_or_invoke (Failable &&failable, Invocable &&invocable) -> std::remove_const_t< std::remove_reference_t< InvocableResult >>
	Get the combination of `failable` and the result of invoking `invocable`. More...

template<typename Visitor , typename Failable , if_is_failable< Failable > = nullptr>
	decltype (auto) resilient::visit(Visitor &&visitor, Failable &&failable)
	Apply a visitor to the `Failable`. More...

template<typename Failable , typename Failure >
Failable	from_failure (Failure &&failure)
	Create a `Failable` with a failure type. More...

template<typename Failable , typename OtherFailable >
Failable	from_narrower_failable (OtherFailable &&failable)
	Construct a `Failable` from another `Failable` with the same `value_type` and a narrower `failure_type`. More...

Detailed Description

template<typename Value, typename Failure>
class resilient::Failable< Value, Failure >

A class to represent the result of an operation which might fail.

A Failable is either a value or a failure. The value is the return value of the invoked function, the failure is an object representing the failure which happened.

Template Parameters

Value	The value.
Failure	The type of the failure.

Constructor & Destructor Documentation

template<typename Value , typename Failure >

template<typename Other , if_is_failable< Other > = nullptr>

resilient::Failable< Value, Failure >::Failable ( Other && other )

inline

Create a Failable from another Failable.

Parameters

other The other Failable.

template<typename Value , typename Failure >

template<typename Other , if_is_not_failable< Other > = nullptr>

resilient::Failable< Value, Failure >::Failable ( Other && other )

inline

Create a Failable from a either a Failure or a Value.

Parameters

other The object to instantiate the Failable with.

Member Function Documentation

template<typename Value , typename Failure >

template<typename Other , if_is_failable< Other > = nullptr>

Failable& resilient::Failable< Value, Failure >::operator= ( Other && other )

inline

Assign the value of another Failable to this Failable.

Parameters

other The other Failable.

Returns: This Failable.

template<typename Value , typename Failure >

template<typename Other , if_is_not_failable< Other > = nullptr>

Failable& resilient::Failable< Value, Failure >::operator= ( Other && other )

inline

Assign an object to this Failable.

Parameters

other The object to assign.

Returns: This Failable.

Friends And Related Function Documentation

template<typename Visitor , typename Failable , if_is_failable< Failable > = nullptr>

decltype	(	Visitor &&	visitor,
		Failable< Value, Failure > &&	failable
	)

Invoke the visitor with either the failure or the value, depending on what the Failable is currently holding.

Parameters

visitor	The visitor to use.
failable	The `Failable` to visit.

Returns: The value returned by the visitor.

template<typename Failable , typename Failure >

Failable from_failure ( Failure && failure )

Template Parameters

Failable The type of the Failable.

Parameters

failure The failure to use.

Returns: Failable The Failable initialized with the failure.

template<typename Failable , typename OtherFailable >

Failable from_narrower_failable ( OtherFailable< Value, Failure > && failable )

A failure_type A is narrower than another type B if the variant which represents it can hold a subset of the types B can hold. For example in using B = resilient::add_failure_to_failable_t<A, NewFailure>, A has a narrower failure_type than B since A can not represent the failure NewFailure.

Template Parameters

Failable The type of the Failable to create.

Parameters

failable The failable to use when creatint the new Failable.

Returns: Failable The Failable initialized from the narrower failable.

template<typename Failable , if_is_failable< Failable > = nullptr>

auto get_failure ( Failable< Value, Failure > && failable ) -> detail::same_const_ref_as_t<Failable, detail::failable_failure_type_t<Failable>>

Precondition: The Failable is currently holding a failure.

Parameters

failable The Failable to get the failure from.

Returns: The failure.

template<typename Failable , if_is_failable< Failable > = nullptr>

auto get_value ( Failable< Value, Failure > && failable ) -> detail::same_const_ref_as_t<Failable, detail::failable_value_type_t<Failable>>

Precondition: The Failable is currently holding a value.

Parameters

failable The Failable to get the value from.

Returns: The value.

template<typename Failable , if_is_failable< Failable > = nullptr>

auto get_value_or	(	Failable< Value, Failure > &&	failable,
		detail::get_value_return_type< Failable< Value, Failure > >	default_value
	)		-> detail::get_value_return_type<Failable>

Parameters

failable	The `Failable` to get the value from if present.
default_value	The default value if a value is not present in `Failable`

Returns: The value in Failable if present, default_value otherwise

template<typename Failable , typename OtherFailable , if_is_failable< Failable > = nullptr, if_is_failable< OtherFailable > = nullptr>

auto get_value_or	(	Failable< Value, Failure > &&	failable,
		OtherFailable< Value, Failure > &&	other
	)		-> std::remove_const_t<std::remove_reference_t<OtherFailable>>

Get the value combining two Failables. The value of the first Failable is preferred. The failure of the second Failable is preferred.

Parameters

failable	A failable
other	A failable with a compatible value_type of `failable`.

Returns: A Failable. It holds the value of failable if it contains a value. It holds the value of other if it contains a value. It holds the failure of other if both failables hold a failure. The returned type is always a value (not a reference).

template<typename Failable , typename Invocable , typename InvocableResult = detail::invoke_result_t<Invocable>, if_is_failable< Failable > = nullptr, detail::if_is_convertible_to_get_value_return_type_of< Failable, InvocableResult > = nullptr>

auto get_value_or_invoke	(	Failable< Value, Failure > &&	failable,
		Invocable &&	invocable
	)		-> detail::get_value_return_type<Failable>

See also: get_value_or()

The function is similar to get_value_or() but allows to compute the default value lazily.

Parameters

failable	The `Failable` to get the value from if present.
invocable	The object to call if failable does not hold a value.

Returns: The value stored in failable or the value returned by invocable.

template<typename Failable , typename Invocable , typename InvocableResult = detail::invoke_result_t<Invocable>, if_is_failable< Failable > = nullptr, if_is_failable< InvocableResult > = nullptr>

auto get_value_or_invoke	(	Failable< Value, Failure > &&	failable,
		Invocable &&	invocable
	)		-> std::remove_const_t<std::remove_reference_t<InvocableResult>>

See also: get_value_or

Equivalent to get_value_or() with a Failable which is provided by lazily calling invocable. invocable is only called if failable does not contain a value.

Parameters

failable	A `Failable`.
invocable	A function which returns a `Failable` with value_type compatible to the one of `failable`.

Returns: The combination of failable and the result of invocable. See get_value_or() for what the result contains.

template<typename Value , typename Failure >

bool holds_failure ( const Failable< Value, Failure > & failable )

Parameters

failable The Failable to check.

Returns: true If the Failable contains the failure.; false If the Failable contains the value.

template<typename Value , typename Failure >

bool holds_value ( const Failable< Value, Failure > & failable )

Parameters

failable The Failable to check.

Returns: true If the Failable contains the value.; false If the Failable contains the failure.

The documentation for this class was generated from the following files:

include/resilient/task/failable.hpp
include/resilient/task/failable_utils.hpp

Public Types

Public Member Functions

Friends

Related Functions

Detailed Description

template<typename Value, typename Failure> class resilient::Failable< Value, Failure >

Constructor & Destructor Documentation

Member Function Documentation

Friends And Related Function Documentation

template<typename Value, typename Failure>
class resilient::Failable< Value, Failure >