cpp::bitwizeshift::result< void, E > Class Template Reference

Partial specialization of result<void, E> More...

#include <result.hpp>

Public Types
using	value_type = void
	The value type of this result.
using	error_type = E
	The error type of this result.
using	failure_type = failure< E >
	The failure type.
template<typename U >
using	rebind = result< U, E >
	Rebinds the result type.

Public Member Functions
constexpr	result () noexcept
	Constructs a result object in a value state. More...
constexpr	result (const result &other)=default
	Copy constructs this result. More...
constexpr	result (result &&other)=default
	Move constructs a result. More...
template<typename U , typename E2 , typename = typename std::enable_if<std::is_constructible<E,E2>::value>::type>
	result (const result< U, E2 > &other) noexcept(std::is_nothrow_constructible< E, const E2 &>::value)
	Converting copy constructor. More...
template<typename U , typename E2 , typename = typename std::enable_if<std::is_constructible<E,E2>::value>::type>
	result (result< U, E2 > &&other) noexcept(std::is_nothrow_constructible< E, E2 &&>::value)
	Converting move constructor. More...
constexpr	result (in_place_t) noexcept
	Constructs a result object in a value state. More...
template<typename... Args, typename = typename std::enable_if<std::is_constructible<E,Args...>::value>::type>
constexpr	result (in_place_error_t, Args &&... args) noexcept(std::is_nothrow_constructible< E, Args... >::value)
	Constructs a result object that contains an error. More...
template<typename U , typename... Args, typename = typename std::enable_if<std::is_constructible<E, std::initializer_list<U>&, Args...>::value>::type>
constexpr	result (in_place_error_t, std::initializer_list< U > ilist, Args &&...args) noexcept(std::is_nothrow_constructible< E, std::initializer_list< U >, Args... >::value)
	Constructs a result object that contains an error. More...
auto	operator= (const result &other) -> result &=default
	Copy assigns the result stored in other. More...
auto	operator= (result &&other) -> result &=default
	Move assigns the result stored in other. More...
template<typename E2 , typename = typename std::enable_if<std::is_nothrow_constructible<E,const E2&>::value && std::is_assignable<E&,const E2&>::value>::type>
auto	operator= (const result< void, E2 > &other) noexcept(std::is_nothrow_assignable< E, const E2 &>::value) -> result &
	Copy-converts the state of other. More...
template<typename E2 , typename = typename std::enable_if<std::is_nothrow_constructible<E,E2&&>::value && std::is_assignable<E&,E2&&>::value>::type>
auto	operator= (result< void, E2 > &&other) noexcept(std::is_nothrow_assignable< E, E2 &&>::value) -> result &
	Move-converts the state of other. More...
RESULT_WARN_UNUSED constexpr	operator bool () const noexcept
	Contextually convertible to true if *this does not contain an error. More...
RESULT_WARN_UNUSED constexpr auto	has_value () const noexcept -> bool
	Returns true if *this contains a value. More...
RESULT_WARN_UNUSED constexpr auto	has_error () const noexcept -> bool
	Returns true if *this contains an error. More...
template<typename U >
RESULT_WARN_UNUSED constexpr auto	and_then (U &&value) const -> result< typename std::decay< U >::type, E >
	Returns a result containing value if this result contains a value, otherwise returns a result containing the current error. More...
template<typename E2 , typename = typename std::enable_if<std::is_constructible<E,const E2&>::value>::type>
constexpr	result (const failure< E2 > &e) noexcept(std::is_nothrow_constructible< E, const E2 &>::value)
	Constructs the underlying error of this result. More...
template<typename E2 , typename = typename std::enable_if<std::is_constructible<E,E2&&>::value>::type>
constexpr	result (failure< E2 > &&e) noexcept(std::is_nothrow_constructible< E, E2 &&>::value)
	Constructs the underlying error of this result. More...
template<typename E2 , typename = typename std::enable_if<detail::result_is_failure_assignable<E,const E2&>::value>::type>
auto	operator= (const failure< E2 > &other) noexcept(std::is_nothrow_assignable< E, const E2 &>::value) -> result &
	Perfect-forwarded assignment. More...
template<typename E2 , typename = typename std::enable_if<detail::result_is_failure_assignable<E,E2&&>::value>::type>
auto	operator= (failure< E2 > &&other) noexcept(std::is_nothrow_assignable< E, E2 &&>::value) -> result &
	Perfect-forwarded assignment. More...
RESULT_CPP14_CONSTEXPR auto	value () &&-> void
	Throws an exception if (*this) is in an error state. More...
RESULT_CPP14_CONSTEXPR auto	value () const &-> void
	Throws an exception if (*this) is in an error state. More...
RESULT_WARN_UNUSED constexpr auto	error () const &noexcept(std::is_nothrow_constructible< E >::value &&std::is_nothrow_copy_constructible< E >::value) -> E
	Returns the contained error, if one exists, or a default-constructed error value. More...
RESULT_WARN_UNUSED RESULT_CPP14_CONSTEXPR auto	error () &&noexcept(std::is_nothrow_constructible< E >::value &&std::is_nothrow_copy_constructible< E >::value) -> E
	Returns the contained error, if one exists, or a default-constructed error value. More...
template<typename String , typename = typename std::enable_if<( std::is_convertible<String,const std::string&>::value && std::is_copy_constructible<E>::value )>::type>
RESULT_CPP14_CONSTEXPR auto	expect (String &&message) const &-> void
	} More...
template<typename String , typename = typename std::enable_if<( std::is_convertible<String,const std::string&>::value && std::is_move_constructible<E>::value )>::type>
RESULT_CPP14_CONSTEXPR auto	expect (String &&message) &&-> void
	} More...
template<typename U >
RESULT_WARN_UNUSED constexpr auto	error_or (U &&default_error) const &-> error_type
	Returns the contained error if *this has an error, otherwise returns default_error. More...
template<typename U >
RESULT_WARN_UNUSED RESULT_CPP14_CONSTEXPR auto	error_or (U &&default_error) &&-> error_type
	Returns the contained error if *this has an error, otherwise returns default_error. More...
template<typename Fn >
RESULT_WARN_UNUSED constexpr auto	flat_map (Fn &&fn) const &-> detail::invoke_result_t< Fn >
	Invokes the function fn if (*this) contains no value. More...
template<typename Fn >
RESULT_WARN_UNUSED RESULT_CPP14_CONSTEXPR auto	flat_map (Fn &&fn) &&-> detail::invoke_result_t< Fn >
	Invokes the function fn if (*this) contains no value. More...
template<typename Fn >
RESULT_WARN_UNUSED constexpr auto	map (Fn &&fn) const &-> result< detail::invoke_result_t< Fn >, E >
	Invokes the function fn if (*this) contains no value. More...
template<typename Fn >
RESULT_WARN_UNUSED RESULT_CPP14_CONSTEXPR auto	map (Fn &&fn) &&-> result< detail::invoke_result_t< Fn >, E >
	Invokes the function fn if (*this) contains no value. More...
template<typename Fn >
constexpr auto	map_error (Fn &&fn) const &-> result< void, detail::invoke_result_t< Fn, const E &>>
	Invokes the function fn with the error of this result as the argument. More...
template<typename Fn >
RESULT_CPP14_CONSTEXPR auto	map_error (Fn &&fn) &&-> result< void, detail::invoke_result_t< Fn, E &&>>
	Invokes the function fn with the error of this result as the argument. More...
template<typename Fn >
RESULT_WARN_UNUSED constexpr auto	flat_map_error (Fn &&fn) const &-> detail::invoke_result_t< Fn, const E &>
	Invokes the function fn with the error of this result as the argument. More...
template<typename Fn >
RESULT_WARN_UNUSED RESULT_CPP14_CONSTEXPR auto	flat_map_error (Fn &&fn) &&-> detail::invoke_result_t< Fn, E &&>
	Invokes the function fn with the error of this result as the argument. More...

Friends
template<typename T2 , typename E2 >
class	result

Detailed Description

template<typename E>
class cpp::bitwizeshift::result< void, E >

Partial specialization of result<void, E>

Template Parameters

E	the underlying error type

Definition at line 2659 of file result.hpp.

Constructor & Destructor Documentation

result() [1/10]

template<typename E >

constexpr cpp::bitwizeshift::result< void, E >::result ( )

noexcept

Constructs a result object in a value state.

Examples

Basic Usage:

auto r = cpp::result<void,int>{};

result() [2/10]

template<typename E >

constexpr cpp::bitwizeshift::result< void, E >::result ( const result< void, E > &  other )

default

Copy constructs this result.

If other contains an error, constructs an object that contains a copy of that error.

Note

This constructor is defined as deleted if std::is_copy_constructible<E>::value is false

This constructor is defined as trivial if both std::is_trivially_copy_constructible<E>::value are true

Examples

Basic Usage:

const auto r = cpp::result<void,int>{};
const auto s = r;

Parameters

other

the result to copy

result() [3/10]

template<typename E >

constexpr cpp::bitwizeshift::result< void, E >::result ( result< void, E > &&  other )

default

Move constructs a result.

If other contains an error, move-constructs this result from that error.

Note

This constructor is defined as deleted if std::is_move_constructible<E>::value is false

This constructor is defined as trivial if both std::is_trivially_move_constructible<E>::value are true

Examples

Basic Usage:

auto r = cpp::result<void,std::string>{};
auto s = std::move(r);

Parameters

other

the result to move

result() [4/10]

template<typename E >

template<typename U , typename E2 , typename = typename std::enable_if<std::is_constructible<E,E2>::value>::type>

cpp::bitwizeshift::result< void, E >::result ( const result< U, E2 > &  other ) const &

explicitnoexcept

Converting copy constructor.

If other contains a value, constructs a result object that is not in an error state – ignoring the value.

If other contains an error, constructs a result object that contains an error, initialized as if direct-initializing (but not direct-list-initializing) an object of type E.

Note

This constructor does not participate in overload resolution unless the following conditions are met:

• std::is_constructible_v<E, const E2&> is true

Examples

Basic Usage:

const auto r = cpp::result<int,int>{42};
const auto s = cpp::result<void,int>{r};

Parameters

other

the other type to convert

result() [5/10]

template<typename E >

template<typename U , typename E2 , typename = typename std::enable_if<std::is_constructible<E,E2>::value>::type>

cpp::bitwizeshift::result< void, E >::result ( result< U, E2 > &&  other ) const &&

explicitnoexcept

Converting move constructor.

If other contains an error, constructs a result object that contains an error, initialized as if direct-initializing (but not direct-list-initializing) an object of type E&&.

Note

This constructor does not participate in overload resolution unless the following conditions are met:

• std::is_constructible_v<E, const E2&> is true

Examples

Basic Usage:

auto r = cpp::result<int,std::string>{42};
auto s = cpp::result<void,std::string>{
  std::move(r)
};

Parameters

other

the other type to convert

result() [6/10]

template<typename E >

constexpr cpp::bitwizeshift::result< void, E >::result ( in_place_t  )

explicitnoexcept

Constructs a result object in a value state.

This constructor exists primarily for symmetry with the result<T,E> constructor. Unlike the T overload, no variadic arguments may be supplied.

Examples

Basic Usage:

auto r = cpp::result<void,std::string>{cpp::in_place};

result() [7/10]

template<typename E >

template<typename... Args, typename = typename std::enable_if<std::is_constructible<E,Args...>::value>::type>

constexpr cpp::bitwizeshift::result< void, E >::result ( in_place_error_t  , Args &&...  args  ) const

explicitnoexcept

Constructs a result object that contains an error.

the value is initialized as if direct-initializing (but not direct-list-initializing) an object of type E from the arguments std::forward<Args>(args)...

Examples

Basic Usage:

auto r = cpp::result<void,std::string>{
  cpp::in_place_error, "Hello world"
};

Parameters

args	the arguments to pass to E's constructor

result() [8/10]

template<typename E >

template<typename U , typename... Args, typename = typename std::enable_if<std::is_constructible<E, std::initializer_list<U>&, Args...>::value>::type>

constexpr cpp::bitwizeshift::result< void, E >::result ( in_place_error_t  , std::initializer_list< U >  ilist, Args &&...  args  ) const

explicitnoexcept

Constructs a result object that contains an error.

The value is initialized as if direct-initializing (but not direct-list-initializing) an object of type E from the arguments std::forward<std::initializer_list<U>>(ilist), std::forward<Args>(args)...

Examples

Basic Usage:

auto r = cpp::result<void,std::string>{
  cpp::in_place_error, {'H','e','l','l','o'}
};

Parameters

ilist	An initializer list of entries to forward
args	the arguments to pass to Es constructor

result() [9/10]

template<typename E >

template<typename E2 , typename = typename std::enable_if<std::is_constructible<E,const E2&>::value>::type>

constexpr cpp::bitwizeshift::result< void, E >::result ( const failure< E2 > &  e ) const &

noexcept

Constructs the underlying error of this result.

Note

This constructor only participates in overload resolution if E is constructible from e

Examples

Basic Usage:

cpp::result<void,int> r = cpp::fail(42);

auto get_error_result() -> cpp::result<void,std::string> {
  return cpp::fail("hello world!");
}

Parameters

e	the failure error

result() [10/10]

template<typename E >

template<typename E2 , typename = typename std::enable_if<std::is_constructible<E,E2&&>::value>::type>

constexpr cpp::bitwizeshift::result< void, E >::result ( failure< E2 > &&  e ) const &&

noexcept

Constructs the underlying error of this result.

Note

This constructor only participates in overload resolution if E is constructible from e

Examples

Basic Usage:

cpp::result<void,int> r = cpp::fail(42);

auto get_error_result() -> cpp::result<void,std::string> {
  return cpp::fail("hello world!");
}

Parameters

e	the failure error

Member Function Documentation

and_then()

template<typename E >

template<typename U >

RESULT_WARN_UNUSED constexpr auto cpp::bitwizeshift::result< void, E >::and_then

(

U &&

value

)

const -> result< typename std::decay< U >::type, E >

Returns a result containing value if this result contains a value, otherwise returns a result containing the current error.

Examples

Basic Usage:

auto r = cpp::result<int,int>{42};
assert(r.and_then(100) == 100);

auto r = cpp::result<int,int>{cpp::fail(42)};
assert(r.and_then(100) == cpp::fail(42));

Parameters

value

the value to return as a result

Returns

a result of value if this contains a value

error() [1/2]

template<typename E >

RESULT_WARN_UNUSED constexpr auto cpp::bitwizeshift::result< void, E >::error ( ) const && -> E

noexcept

Returns the contained error, if one exists, or a default-constructed error value.

The error() function will not throw any exceptions if E does not throw any exceptions for the copy or move construction.

This is to limit the possible scope for exceptions, and to allow the error type to be treated as a "status"-like type, where the default-constructed case is considered the "good" state.

If this function is invoked on an rvalue of a result, the error is returned via move-construction

Requires

• std::is_default_constructible<E>::value is true
• std::is_copy_constructible<E>::value or std::is_move_constructible<E>::value is true
• E{} represents the "good" (non-error) state

Examples

Basic Usage:

auto r = cpp::result<int,std::error_code>{ 42 };
assert(r.error() == std::error_code{});

auto r = cpp::result<int,std::error_code>{
  cpp::fail(std::io_errc::stream)
};

assert(r.error() == std::io_errc::stream);

Returns

the error or a default-constructed error value

error() [2/2]

template<typename E >

RESULT_WARN_UNUSED RESULT_CPP14_CONSTEXPR auto cpp::bitwizeshift::result< void, E >::error ( ) const && -> E

noexcept

Returns the contained error, if one exists, or a default-constructed error value.

The error() function will not throw any exceptions if E does not throw any exceptions for the copy or move construction.

This is to limit the possible scope for exceptions, and to allow the error type to be treated as a "status"-like type, where the default-constructed case is considered the "good" state.

If this function is invoked on an rvalue of a result, the error is returned via move-construction

Requires

• std::is_default_constructible<E>::value is true
• std::is_copy_constructible<E>::value or std::is_move_constructible<E>::value is true
• E{} represents the "good" (non-error) state

Examples

Basic Usage:

auto r = cpp::result<int,std::error_code>{ 42 };
assert(r.error() == std::error_code{});

auto r = cpp::result<int,std::error_code>{
  cpp::fail(std::io_errc::stream)
};

assert(r.error() == std::io_errc::stream);

Returns

the error or a default-constructed error value

error_or() [1/2]

template<typename E >

template<typename U >

RESULT_WARN_UNUSED constexpr auto cpp::bitwizeshift::result< void, E >::error_or

(

U &&

default_error

)

const & -> error_type

Returns the contained error if *this has an error, otherwise returns default_error.

Examples

Basic Usage:

auto r = cpp::result<int,int>{42};
assert(r.error_or(0) == cpp::fail(0));

auto r = cpp::result<int,int>{cpp::fail(42)};
assert(r.error_or(0) == cpp::fail(42));

Parameters

default_error

the error to use in case *this is empty

Returns

the contained value or default_error

error_or() [2/2]

template<typename E >

template<typename U >

RESULT_WARN_UNUSED RESULT_CPP14_CONSTEXPR auto cpp::bitwizeshift::result< void, E >::error_or

(

U &&

default_error

)

&& -> error_type

Returns the contained error if *this has an error, otherwise returns default_error.

Examples

Basic Usage:

auto r = cpp::result<int,int>{42};
assert(r.error_or(0) == cpp::fail(0));

auto r = cpp::result<int,int>{cpp::fail(42)};
assert(r.error_or(0) == cpp::fail(42));

Parameters

default_error

the error to use in case *this is empty

Returns

the contained value or default_error

expect() [1/2]

template<typename E >

template<typename String , typename = typename std::enable_if<( std::is_convertible<String,const std::string&>::value && std::is_copy_constructible<E>::value )>::type>

RESULT_CPP14_CONSTEXPR auto cpp::bitwizeshift::result< void, E >::expect

(

String &&

message

)

const & -> void

}

Asserts an expectation that this result contains an error, throwing a bad_result_access on failure

If this function is invoked from an rvalue of result, then this will consume the underlying error first, if there is one.

Note

This function exists as a means to allow for results to be marked used without requiring directly inspecting the underlying value. This is, in effect, equivalent to assert(res.has_value()), however it uses exceptions to ensure the stack can be unwound, and exceptions invoked.

Examples

Basic Usage:

auto start_service() -> cpp::result<void,int>;

start_service().expect("Service failed to start!");

Parameters

message

the message to provide to this expectation

expect() [2/2]

template<typename E >

template<typename String , typename = typename std::enable_if<( std::is_convertible<String,const std::string&>::value && std::is_move_constructible<E>::value )>::type>

RESULT_CPP14_CONSTEXPR auto cpp::bitwizeshift::result< void, E >::expect

(

String &&

message

)

&& -> void

}

Asserts an expectation that this result contains an error, throwing a bad_result_access on failure

If this function is invoked from an rvalue of result, then this will consume the underlying error first, if there is one.

Note

This function exists as a means to allow for results to be marked used without requiring directly inspecting the underlying value. This is, in effect, equivalent to assert(res.has_value()), however it uses exceptions to ensure the stack can be unwound, and exceptions invoked.

Examples

Basic Usage:

auto start_service() -> cpp::result<void,int>;

start_service().expect("Service failed to start!");

Parameters

message

the message to provide to this expectation

flat_map() [1/2]

template<typename E >

template<typename Fn >

RESULT_WARN_UNUSED constexpr auto cpp::bitwizeshift::result< void, E >::flat_map

(

Fn &&

fn

)

const & -> detail::invoke_result_t< Fn >

Invokes the function fn if (*this) contains no value.

If this result contains an error, a result of the error is returned

The function being called must return a result type or the program is ill-formed

If this is called on an rvalue of result which contains an error, the returned result is constructed from an rvalue of that error.

Examples

Basic Usage:

auto generate_int() -> cpp::result<int,int> { return 42; }
auto r = cpp::result<void,int>{};
assert(r.flat_map(generate_int) == 42);

auto r = cpp::result<void,int>{cpp::fail(42)};
assert(r.flat_map(generate_int) == cpp::fail(42));

Parameters

fn	the function to invoke with this

Returns

The result of the function being called

flat_map() [2/2]

template<typename E >

template<typename Fn >

RESULT_WARN_UNUSED RESULT_CPP14_CONSTEXPR auto cpp::bitwizeshift::result< void, E >::flat_map

(

Fn &&

fn

)

&& -> detail::invoke_result_t< Fn >

Invokes the function fn if (*this) contains no value.

If this result contains an error, a result of the error is returned

The function being called must return a result type or the program is ill-formed

If this is called on an rvalue of result which contains an error, the returned result is constructed from an rvalue of that error.

Examples

Basic Usage:

auto generate_int() -> cpp::result<int,int> { return 42; }
auto r = cpp::result<void,int>{};
assert(r.flat_map(generate_int) == 42);

auto r = cpp::result<void,int>{cpp::fail(42)};
assert(r.flat_map(generate_int) == cpp::fail(42));

Parameters

fn	the function to invoke with this

Returns

The result of the function being called

flat_map_error() [1/2]

template<typename E >

template<typename Fn >

RESULT_WARN_UNUSED constexpr auto cpp::bitwizeshift::result< void, E >::flat_map_error

(

Fn &&

fn

)

const & -> detail::invoke_result_t< Fn, const E &>

Invokes the function fn with the error of this result as the argument.

If this result contains a value, a result of the value is returned

The function being called must return a result type or the program is ill-formed

If this is called on an rvalue of result which contains an error, the returned result is constructed from an rvalue of that error.

Examples

Basic Usage:

auto to_string(int) -> cpp::result<int,std::string>;
auto r = cpp::result<int,int>{42};
assert(r.flat_map(to_string) == 42);

auto r = cpp::result<int,int>{cpp::fail(42)};
assert(r.flat_map(to_string) == cpp::fail("42"));

Parameters

fn	the function to invoke with this

Returns

The result of the function being called

flat_map_error() [2/2]

template<typename E >

template<typename Fn >

RESULT_WARN_UNUSED RESULT_CPP14_CONSTEXPR auto cpp::bitwizeshift::result< void, E >::flat_map_error

(

Fn &&

fn

)

&& -> detail::invoke_result_t< Fn, E &&>

Invokes the function fn with the error of this result as the argument.

If this result contains a value, a result of the value is returned

The function being called must return a result type or the program is ill-formed

If this is called on an rvalue of result which contains an error, the returned result is constructed from an rvalue of that error.

Examples

Basic Usage:

auto to_string(int) -> cpp::result<int,std::string>;
auto r = cpp::result<int,int>{42};
assert(r.flat_map(to_string) == 42);

auto r = cpp::result<int,int>{cpp::fail(42)};
assert(r.flat_map(to_string) == cpp::fail("42"));

Parameters

fn	the function to invoke with this

Returns

The result of the function being called

has_error()

template<typename E >

RESULT_WARN_UNUSED constexpr auto cpp::bitwizeshift::result< void, E >::has_error ( ) const -> bool

noexcept

Returns true if *this contains an error.

Examples

Basic Usage:

auto get_result() -> cpp::result<int, int>;

auto r = get_result();
if (r.has_error()) { ... }

assert(!cpp::result<int,int>{42}.has_error());

assert(cpp::result<int,int>{cpp::fail(42)}.has_error());

Returns

true if *this contains an error, false if *this contains a value

has_value()

template<typename E >

RESULT_WARN_UNUSED constexpr auto cpp::bitwizeshift::result< void, E >::has_value ( ) const -> bool

noexcept

Returns true if *this contains a value.

Examples

Basic Usage:

auto get_result() -> cpp::result<int, int>;
auto r = get_result();
if (r.has_value()) { ... }

assert(cpp::result<int,int>{42}.has_value());

assert(!cpp::result<int,int>{cpp::fail(42)}.has_value());

Returns

true if *this contains a value, false if *this contains an error

map() [1/2]

template<typename E >

template<typename Fn >

RESULT_WARN_UNUSED constexpr auto cpp::bitwizeshift::result< void, E >::map

(

Fn &&

fn

)

const & -> result< detail::invoke_result_t< Fn >, E >

Invokes the function fn if (*this) contains no value.

If this result is an error, the result of this function is that error. Otherwise this function wraps the result and returns it as an result.

If this is called on an rvalue of result which contains an error, the returned result is constructed from an rvalue of that error.

Examples

Basic Usage:

auto generate_int() -> int { return 42; }
auto r = cpp::result<void,int>{};
assert(r.map(generate_int) == 42);

auto r = cpp::result<void,int>{cpp::fail(42)};
assert(r.map(generate_int) == cpp::fail(42));

Parameters

fn	the function to invoke with this

Returns

The result result of the function invoked

map() [2/2]

template<typename E >

template<typename Fn >

RESULT_WARN_UNUSED RESULT_CPP14_CONSTEXPR auto cpp::bitwizeshift::result< void, E >::map

(

Fn &&

fn

)

&& -> result< detail::invoke_result_t< Fn >, E >

Invokes the function fn if (*this) contains no value.

If this result is an error, the result of this function is that error. Otherwise this function wraps the result and returns it as an result.

If this is called on an rvalue of result which contains an error, the returned result is constructed from an rvalue of that error.

Examples

Basic Usage:

auto generate_int() -> int { return 42; }
auto r = cpp::result<void,int>{};
assert(r.map(generate_int) == 42);

auto r = cpp::result<void,int>{cpp::fail(42)};
assert(r.map(generate_int) == cpp::fail(42));

Parameters

fn	the function to invoke with this

Returns

The result result of the function invoked

map_error() [1/2]

template<typename E >

template<typename Fn >

constexpr auto cpp::bitwizeshift::result< void, E >::map_error

(

Fn &&

fn

)

const & -> result< void, detail::invoke_result_t< Fn, const E &>>

Invokes the function fn with the error of this result as the argument.

If this result contains a value, the result of this function is that value. Otherwise the function is called with that error and returns the result as a result.

If this is called on an rvalue of result which contains a value, the returned result is constructed from an rvalue of that value.

Examples

Basic Usage:

auto to_string(int) -> std::string;
auto r = cpp::result<int,int>{42};
assert(r.map_error(to_string) == 42);

auto r = cpp::result<int,int>{cpp::fail(42)};
assert(r.map_error(to_string) == cpp::fail("42"));

auto r = cpp::result<std::string,int>{};
auto s = r.map(std::string::size); // 's' contains 'result<size_t,int>'

Parameters

fn	the function to invoke with this

Returns

The result result of the function invoked

map_error() [2/2]

template<typename E >

template<typename Fn >

RESULT_CPP14_CONSTEXPR auto cpp::bitwizeshift::result< void, E >::map_error

(

Fn &&

fn

)

&& -> result< void, detail::invoke_result_t< Fn, E &&>>

Invokes the function fn with the error of this result as the argument.

If this result contains a value, the result of this function is that value. Otherwise the function is called with that error and returns the result as a result.

If this is called on an rvalue of result which contains a value, the returned result is constructed from an rvalue of that value.

Examples

Basic Usage:

auto to_string(int) -> std::string;
auto r = cpp::result<int,int>{42};
assert(r.map_error(to_string) == 42);

auto r = cpp::result<int,int>{cpp::fail(42)};
assert(r.map_error(to_string) == cpp::fail("42"));

auto r = cpp::result<std::string,int>{};
auto s = r.map(std::string::size); // 's' contains 'result<size_t,int>'

Parameters

fn	the function to invoke with this

Returns

The result result of the function invoked

operator bool()

template<typename E >

RESULT_WARN_UNUSED constexpr cpp::bitwizeshift::result< void, E >::operator bool ( ) const

explicitnoexcept

Contextually convertible to true if *this does not contain an error.

This function exists to allow for simple, terse checks for containing a value.

Examples

Basic Usage:

auto get_result() -> cpp::result<void, int>;
auto r = get_result();
if (r) { ... }

assert(static_cast<bool>(cpp::result<void,int>{}));

assert(!static_cast<bool>(cpp::result<void,int>{cpp::fail(42)}));

Returns

true if *this contains a value, false if *this does not contain a value

operator=() [1/6]

template<typename E >

auto cpp::bitwizeshift::result< void, E >::operator= ( const result< void, E > &  other ) -> result &=default

default

Copy assigns the result stored in other.

Note

The function does not participate in overload resolution unless

• std::is_nothrow_copy_constructible_v<E> is true this restriction guarantees that no 'valueless_by_exception` state may occur.

This assignment operator is defined as trivial if the following conditions are all true:

• std::is_trivially_copy_constructible<E>::value
• std::is_trivially_copy_assignable<E>::value
• std::is_trivially_destructible<E>::value

Parameters

other

the other result to copy

operator=() [2/6]

template<typename E >

auto cpp::bitwizeshift::result< void, E >::operator= ( result< void, E > &&  other ) -> result &=default

default

Move assigns the result stored in other.

Note

The function does not participate in overload resolution unless

• std::is_nothrow_copy_constructible_v<E> is true this restriction guarantees that no 'valueless_by_exception` state may occur.

This assignment operator is defined as trivial if the following conditions are all true:

• std::is_trivially_move_constructible<E>::value
• std::is_trivially_move_assignable<E>::value
• std::is_trivially_destructible<E>::value

Parameters

other

the other result to copy

operator=() [3/6]

template<typename E >

template<typename E2 , typename = typename std::enable_if<std::is_nothrow_constructible<E,const E2&>::value && std::is_assignable<E&,const E2&>::value>::type>

auto cpp::bitwizeshift::result< void, E >::operator= ( const result< void, E2 > &  other ) const & -> result &

noexcept

Copy-converts the state of other.

If both this and other contain an error, the underlying error is assigned through copy-assignment.

If other contains a value state, this result is constructed in a value state.

If other contans an error state, and this contains a value state, the underlying error is constructed through copy-construction.

Note

The function does not participate in overload resolution unless

• std::is_nothrow_constructible_v<E, const E2&>, std::is_assignable_v<E&, const E2&> are all true.

Parameters

other

the other result object to convert

Returns

reference to (*this)

operator=() [4/6]

template<typename E >

template<typename E2 , typename = typename std::enable_if<std::is_nothrow_constructible<E,E2&&>::value && std::is_assignable<E&,E2&&>::value>::type>

auto cpp::bitwizeshift::result< void, E >::operator= ( result< void, E2 > &&  other ) && -> result &

noexcept

Move-converts the state of other.

If both this and other contain an error, the underlying error is assigned through move-assignment.

If other contains a value state, this result is constructed in a value state.

If other contans an error state, and this contains a value state, the underlying error is constructed through move-construction.

Note

The function does not participate in overload resolution unless

• std::is_nothrow_constructible_v<E, E2&&>, std::is_assignable_v<E&, E2&&> are all true.

Parameters

other

the other result object to convert

Returns

reference to (*this)

operator=() [5/6]

template<typename E >

template<typename E2 , typename = typename std::enable_if<detail::result_is_failure_assignable<E,const E2&>::value>::type>

auto cpp::bitwizeshift::result< void, E >::operator= ( const failure< E2 > &  other ) const & -> result &

noexcept

Perfect-forwarded assignment.

Depending on whether *this contains an error before the call, the contained error is either direct-initialized via forwarding the error, or assigned from forwarding the error

Note

The function does not participate in overload resolution unless

• std::is_nothrow_constructible_v<E, E2> is true, and
• std::is_assignable_v<E&, E2> is true

Parameters

other

the failure value to assign to this

Returns

reference to (*this)

operator=() [6/6]

template<typename E >

template<typename E2 , typename = typename std::enable_if<detail::result_is_failure_assignable<E,E2&&>::value>::type>

auto cpp::bitwizeshift::result< void, E >::operator= ( failure< E2 > &&  other ) && -> result &

noexcept

Perfect-forwarded assignment.

Depending on whether *this contains an error before the call, the contained error is either direct-initialized via forwarding the error, or assigned from forwarding the error

Note

The function does not participate in overload resolution unless

• std::is_nothrow_constructible_v<E, E2> is true, and
• std::is_assignable_v<E&, E2> is true

Parameters

other

the failure value to assign to this

Returns

reference to (*this)

value() [1/2]

template<typename E >

RESULT_CPP14_CONSTEXPR auto cpp::bitwizeshift::result< void, E >::value

(

)

&& -> void

Throws an exception if (*this) is in an error state.

This function exists for symmetry with cpp::result<T,E> objects where T contains a value.

If this contains an error, an exception is thrown containing the underlying error. The error is consumed propagating the same constness and refness of this result.

Examples

Basic Usage:

cpp::result<void,int>{}.value(); // no exception

auto r = cpp::result<void,std::unique_ptr<int>>{
  cpp::fail(std::make_unique<int>(42))
};
std::move(r).value(); // throws bad_result_access<std::unique_ptr<int>>

try {
  auto r = cpp::result<void,int>{ cpp::fail(42) }.value();
} catch (const cpp::bad_result_access<int>& e) {
  assert(e.error() == 42);
}

Exceptions

bad_result_access<E>

if *this does not contain a value.

value() [2/2]

template<typename E >

RESULT_CPP14_CONSTEXPR auto cpp::bitwizeshift::result< void, E >::value

(

)

const & -> void

Throws an exception if (*this) is in an error state.

This function exists for symmetry with cpp::result<T,E> objects where T contains a value.

If this contains an error, an exception is thrown containing the underlying error. The error is consumed propagating the same constness and refness of this result.

Examples

Basic Usage:

cpp::result<void,int>{}.value(); // no exception

auto r = cpp::result<void,std::unique_ptr<int>>{
  cpp::fail(std::make_unique<int>(42))
};
std::move(r).value(); // throws bad_result_access<std::unique_ptr<int>>

try {
  auto r = cpp::result<void,int>{ cpp::fail(42) }.value();
} catch (const cpp::bad_result_access<int>& e) {
  assert(e.error() == 42);
}

Exceptions

bad_result_access<E>

if *this does not contain a value.

---

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

• include/result.hpp