result.hpp

result.hpp #

result.hpp defines the result type, which can hold either a success value or a failure value.

This is used as the return type for toml::try_parse, which does not throw exceptions.

success #

A type that holds a success value.

namespace toml
{
template<typename T>
struct success
{
    using value_type = T;

    explicit success(value_type v);

    ~success() = default;
    success(const success&) = default;
    success(success&&)      = default;
    success& operator=(const success&) = default;
    success& operator=(success&&)      = default;

    template<typename U>
    explicit success(U&& v);
    template<typename U>
    explicit success(success<U> v);

    value_type&       get()       noexcept;
    value_type const& get() const noexcept;
};

template<typename T>
success<typename std::decay<T>::type> ok(T&& v);
template<std::size_t N>
success<std::string> ok(const char (&literal)[N])
}

Member Types #

using value_type = T;

The type of the success value.

Member Functions #

Constructor #

explicit success(value_type v);

Constructs with a value_type argument.

template<typename U>
explicit success(U&& v);

Constructs with another type that can be converted to value_type.

template<typename U>
explicit success(success<U> v);

Constructs with another success type that can be converted to value_type.

get() #

value_type&       get()       noexcept;
value_type const& get() const noexcept;

Accesses the stored value.

Non-Member Functions #

ok(T) #

template<typename T>
success<typename std::decay<T>::type> ok(T&& v);
template<std::size_t N>
success<std::string> ok(const char (&literal)[N]);

Constructs and returns a success type from a success value.

Converts a string literal into std::string.

success<reference_wrapper<T>> #

Specialization of success for when the success value is a reference.

namespace toml
{
template<typename T>
struct success<std::reference_wrapper<T>>
{
    using value_type = T;

    explicit success(std::reference_wrapper<value_type> v) noexcept;

    value_type&       get()       noexcept;
    value_type const& get() const noexcept;
};
}

Member Types #

using value_type = T;

The type of the success value. It is T from std::reference_wrapper<T>, not the reference itself.

get() #

value_type&       get()       noexcept;
value_type const& get() const noexcept;

Accesses the stored value.

failure #

A type that holds a failure value.

namespace toml
{
template<typename T>
struct failure
{
    using value_type = T;

    explicit failure(value_type v);

    ~failure() = default;
    failure(const failure&) = default;
    failure(failure&&)      = default;
    failure& operator=(const failure&) = default;
    failure& operator=(failure&&)      = default;

    template<typename U>
    explicit failure(U&& v);
    template<typename U>
    explicit failure(failure<U> v);

    value_type&       get()       noexcept;
    value_type const& get() const noexcept;
};

template<typename T>
failure<typename std::decay<T>::type> err(T&& v);
template<std::size_t N>
failure<std::string> err(const char (&literal)[N]);
}

Member Types #

using value_type = T;

The type of the failure value.

Member Functions #

Constructor #

explicit failure(value_type v);

Constructs with a value_type argument.

template<typename U>
explicit failure(U&& v);

Constructs with another type that can be converted to value_type.

template<typename U>
explicit failure(failure<U> v);

Constructs with another failure type that can be converted to value_type.

get() #

value_type&       get()       noexcept;
value_type const& get() const noexcept;

Accesses the stored value.

Non-Member Functions #

err(T) #

template<typename T>
failure<typename std::decay<T>::type> err(T&& v);
template<std::size_t N>
failure<std::string> err(const char (&literal)[N]);

Constructs and returns a failure type from a failure value.

Converts a string literal into std::string.

failure<reference_wrapper<T>> #

Specialization of failure for when the failure value is a reference.

namespace toml
{
template<typename T>
struct failure<std::reference_wrapper<T>>
{
    using value_type = T;

    explicit failure(std::reference_wrapper<value_type> v) noexcept;

    value_type&       get()       noexcept {return value.get();}
    value_type const& get() const noexcept {return value.get();}
};
}

Member Types #

using value_type = T;

The type of the failure value. It is T from std::reference_wrapper<T>, not the reference itself.

get() #

value_type&       get()       noexcept;
value_type const& get() const noexcept;

Accesses the stored value.

result #

A type that holds either a success value or a failure value.

namespace toml
{
template<typename T, typename E>
struct result
{
    using success_type = success<T>;
    using failure_type = failure<E>;
    using value_type = typename success_type::value_type;
    using error_type = typename failure_type::value_type;

    result(success_type s);
    result(failure_type f);

    template<typename U>
    result(success<U> s);
    template<typename U>
    result(failure<U> f);

    result& operator=(success_type s);
    result& operator=(failure_type f);

    template<typename U>
    result& operator=(success<U> s);
    template<typename U>
    result& operator=(failure<U> f);

    ~result() noexcept;

    result(const result& other);
    result(result&& other);
    result& operator=(const result& other);
    result& operator=(result&& other);

    template<typename U, typename F>
    result(result<U, F> other);
    template<typename U, typename F>
    result& operator=(result<U, F> other);

    bool is_ok()  const noexcept;
    bool is_err() const noexcept;

    explicit operator bool() const noexcept;

    value_type&       unwrap(cxx::source_location loc = cxx::source_location::current());
    value_type const& unwrap(cxx::source_location loc = cxx::source_location::current()) const;

    value_type&       unwrap_or(value_type& opt)             noexcept;
    value_type const& unwrap_or(value_type const& opt) const noexcept;

    error_type&       unwrap_err(cxx::source_location loc = cxx::source_location::current());
    error_type const& unwrap_err(cxx::source_location loc = cxx::source_location::current()) const;

    value_type&       as_ok()       noexcept;
    value_type const& as_ok() const noexcept;

    error_type&       as_err()       noexcept;
    error_type const& as_err() const noexcept;
};
}

Member Types #

success_type #

success<T>.

failure_type #

failure<E>.

value_type #

The type T of the success value, alias for success_type::value_type.

If T is std::reference_wrapper<U>, then it is U.

error_type #

The type E of the failure value, alias for failure_type::value_type.

If E is std::reference_wrapper<F>, then it is F.

Member Functions #

Constructor #

result() = delete;

Cannot construct result type by default. Needs to be given either a success or failure type.

result(success_type s);
result(failure_type f);

Constructs with a success_type or failure_type.

template<typename U>
result(success<U> s);
template<typename U>
result(failure<U> f);

Constructs with a success<U> or failure<U> that is convertible to value_type or error_type.

template<typename U, typename F>
result(result<U, F> other);
template<typename U, typename F>
result& operator=(result<U, F> other);

Constructs from or assigns to another result with convertible success or failure types.

Copy and Move Constructors #

result(const result& other);
result(result&& other);

Can be copy or move constructed.

operator= #

result& operator=(const result& other);
result& operator=(result&& other);

Can be copy or move assigned.

template<typename U>
result& operator=(success<U> s);
template<typename U>
result& operator=(failure<U> f);

Can be assigned from convertible success or failure types.

is_ok() #

bool is_ok()  const noexcept;

Returns true if it holds a success value, false otherwise.

is_err() #

bool is_err() const noexcept;

Returns true if it holds a failure value, false otherwise.

operator bool() #

explicit operator bool() const noexcept;

Returns true if it holds a success value, false otherwise.

unwrap() #

value_type&       unwrap(cxx::source_location loc = cxx::source_location::current());
value_type const& unwrap(cxx::source_location loc = cxx::source_location::current()) const;

Returns the stored success value.

Throws toml::bad_result_access if it holds a failure value.

If std::source_location or equivalent compiler extension is available, the file name and line number where unwrap() occurred are included in the what() string.

unwrap_or() #

value_type&       unwrap_or(value_type& opt)             noexcept;
value_type const& unwrap_or(value_type const& opt) const noexcept;

Returns the stored success value if present, otherwise returns the provided default value.

unwrap_err() #

error_type&       unwrap_err(cxx::source_location loc = cxx::source_location::current());
error_type const& unwrap_err(cxx::source_location loc = cxx::source_location::current()) const;

Returns the stored failure value.

Throws toml::bad_result_access if it holds a success value.

If std::source_location or equivalent compiler extension is available, the file name and line number where unwrap_err() occurred are included in the what() string.

as_ok() #

value_type&       as_ok()       noexcept;
value_type const& as_ok() const noexcept;

Returns the success value without checking.

Behavior is undefined if it holds a failure value.

as_err() #

error_type&       as_err()       noexcept;
error_type const& as_err() const noexcept;

Returns the failure value without checking.

Behavior is undefined if it holds a success value.

bad_result_access #

An exception thrown when unwrap or unwrap_err fails in a result.

namespace toml
{
struct bad_result_access : public ::toml::exception
{
  public:
    explicit bad_result_access(const std::string& what_arg);
    virtual ~bad_result_access() noexcept override = default;
    virtual const char* what() const noexcept override;
  protected:
    std::string what_;
};
}