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- <div class="titlepage"><div><div><h1 style="clear: both"><code>basic_result<T, E, NoValuePolicy></code></h1></div></div></div>
- <div class="toc"><dl class="toc">
- <dt>
- <dd><dl>
- <dt>
- <dd><dl>
- <dt><a href="#design-rationale">Design rationale</a></dt>
- <dt><a href="#public-member-type-aliases">Public member type aliases</a></dt>
- <dt><a href="#protected-member-predicate-booleans">Protected member predicate booleans</a>
- <dd><dl>
- <dt><a href="#summary-of-standard-requirements-provided-https-en-cppreference-com-w-cpp-named-req">Summary of <a href="https://en.cppreference.com/w/cpp/named_req">standard requirements provided</a></a></dt>
- </dl></dd></dt>
- <dt><a href="#public-member-functions">Public member functions</a>
- <dd><dl>
- <dt><a href="#disabling-constructors">Disabling constructors</a></dt>
- </dl></dd></dt>
- </dl></dd></dt>
- </dl></dd></dt>
- </dl>
- </div>
- <p>A sum type carrying either a <code>T</code> or an <code>E</code>, with <code>NoValuePolicy</code> specifying what to do if one tries to read state which isn’t there. Either or both of <code>T</code> and <code>E</code> can be <code>void</code> to indicate no value for that state is present. Note that <code>E = void</code> makes basic result into effectively an <code>optional<T></code>, but with <code>NoValuePolicy</code> configurable behaviour. Detectable using <a href="../../reference/traits/is_basic_result.html" class="api-reference"><code>is_basic_result<T></code></a>
- .</p>
- <p><em>Requires</em>: Concept requirements if C++ 20, else static asserted:</p>
- <ul>
- <li>That trait <a href="../../reference/traits/type_can_be_used_in_basic_result.html" class="api-reference"><code>type_can_be_used_in_basic_result<R></code></a>
- is true for both <code>T</code> and <code>E</code>.</li>
- <li>That either <code>E</code> is <code>void</code> or <code>DefaultConstructible</code>.</li>
- </ul>
- <p><em>Namespace</em>: <code>BOOST_OUTCOME_V2_NAMESPACE</code></p>
- <p><em>Header</em>: <code><boost/outcome/basic_result.hpp></code></p>
- <p><em>Inclusions</em>: The very lightest weight of C and C++ header files:</p>
- <ol>
- <li><code><cstdint></code></li>
- <li><code><initializer_list></code></li>
- <li><code><iosfwd></code></li>
- <li><code><new></code></li>
- <li><code><type_traits></code></li>
- <li>If <a href="../../reference/macros/in_place_type.html" class="api-reference"><code>BOOST_OUTCOME_USE_STD_IN_PLACE_TYPE</code></a>
- is <code>1</code>, <code><utility></code> (defaults to <code>1</code> for C++ 17 or later only)</li>
- <li>If C++ exceptions disabled and <code>BOOST_OUTCOME_DISABLE_EXECINFO</code> undefined only (used to print stack backtraces on “exception throw”):
- <ol>
- <li><code><sal.h></code> (Windows only)</li>
- <li><code><stddef.h></code> (Windows only)</li>
- <li><code><string.h></code> (Windows only)</li>
- <li><code><execinfo.h></code> (POSIX only)</li>
- </ol></li>
- <li><code><cstdio></code></li>
- <li><code><cstdlib></code></li>
- <li><code><cassert></code></li>
- </ol>
- <p>This very light weight set of inclusion dependencies makes basic result suitable for use in global header files of very large C++ codebases.</p>
- <h3 id="design-rationale">Design rationale</h3>
- <p>The basic result type is the main workhorse type of the Outcome library, providing a simple sum type with optional values representing success or disappointment. Unlike
- <a href="https://wg21.link/P0323" class="api-reference" target="_blank"><i class="fa fa-book" aria-hidden="true"></i> P0323 <code>std::expected<T, E></code></a>
- , Outcome’s result type is designed specifically for convenience when implementing failure handling across very large codebases, and it has a number of API differences to facilitate that.</p>
- <p>The first major design difference is that basic result models its constructor design on
- <a href="https://en.cppreference.com/w/cpp/utility/variant" class="api-reference" target="_blank"><i class="fa fa-book" aria-hidden="true"></i> <code>std::variant<...></code></a>
- , rather than modelling
- <a href="https://en.cppreference.com/w/cpp/utility/optional" class="api-reference" target="_blank"><i class="fa fa-book" aria-hidden="true"></i> <code>std::optional<T></code></a>
- ’s constructor design like <code>std::expected<T, E></code> does. This means that basic result will implicitly construct either a <code>T</code> or an <code>E</code> if doing so is unambiguous, same as <code>variant</code> does. Where implicit construction is ambiguous, the implicit constructors disable and a <code>T</code> or <code>E</code> can be specified via <a href="../../reference/types/in_place_type_t.html" class="api-reference"><code>in_place_type_t<T></code></a>
- , or via <a href="../../reference/types/success_type.html" class="api-reference"><code>success_type<T></code></a>
- or <a href="../../reference/traits/is_failure_type.html" class="api-reference"><code>failure_type<T></code></a>
- . We implement a subset of variant’s constructors for improved compile time impact, so the implicit and explicit constructor design is split into fixed subsets to reduce SFINAE execution.</p>
- <p>The second major design difference is that union storage is NOT used, as it is assumed that <code>sizeof(E)</code> will be small for failure handling. This very considerably reduces load on the compiler, and substantially improves compile times in very large C++ 14 codebases, because copies and moves do not need to jump through complex ceremony in order to implement the never-empty guarantees which would be required in a union storage based implementation (C++ 17 onwards does far fewer copy and move constructor instantiations, but it all adds up – work avoided is always the fastest).</p>
- <h3 id="public-member-type-aliases">Public member type aliases</h3>
- <ul>
- <li><code>value_type</code> is <code>T</code>.</li>
- <li><code>error_type</code> is <code>E</code>.</li>
- <li><code>value_type_if_enabled</code> is <code>T</code> if construction from <code>T</code> is available, else it is a usefully named unusable internal type.</li>
- <li><code>error_type_if_enabled</code> is <code>E</code> if construction from <code>E</code> is available, else it is a usefully named unusable internal type.</li>
- <li><code>rebind<A, B = E, C = NoValuePolicy></code> is <code>basic_result<A, B, C></code>.</li>
- </ul>
- <h3 id="protected-member-predicate-booleans">Protected member predicate booleans</h3>
- <ul>
- <li><p><code>predicate::constructors_enabled</code> is constexpr boolean true if decayed <code>value_type</code> and decayed <code>error_type</code> are not the same type.</p></li>
- <li><p><code>predicate::implicit_constructors_enabled</code> is constexpr boolean true if:</p>
- <ol>
- <li><code>predicate::constructors_enabled</code> is true.</li>
- <li>Trait <a href="../../reference/traits/is_error_type.html" class="api-reference"><code>is_error_type<E></code></a>
- is not true for both decayed <code>value_type</code> and decayed <code>error_type</code> at the same time.</li>
- <li><code>value_type</code> is not implicitly constructible from <code>error_type</code> and <code>error_type</code> is not implicitly constructible from <code>value_type</code>.<br>OR<br>trait <a href="../../reference/traits/is_error_type.html" class="api-reference"><code>is_error_type<E></code></a>
- is true for decayed <code>error_type</code> and <code>error_type</code> is not implicitly constructible from <code>value_type</code> and <code>value_type</code> is an integral type.</li>
- </ol></li>
- <li><p><code>predicate::enable_value_converting_constructor<A></code> is constexpr boolean true if:</p>
- <ol>
- <li><code>predicate::constructors_enabled</code> is true.</li>
- <li>Decayed <code>A</code> is not this <code>basic_result</code> type.</li>
- <li><code>predicate::implicit_constructors_enabled</code> is true.</li>
- <li>Decayed <code>A</code> is not an <code>in_place_type_t</code>.</li>
- <li>Trait <a href="../../reference/traits/is_error_type_enum.html" class="api-reference"><code>is_error_type_enum<E, Enum></code></a>
- is false for <code>error_type</code> and decayed <code>A</code>.</li>
- <li><code>value_type</code> is implicitly constructible from <code>A</code> and <code>error_type</code> is not implicitly constructible from <code>A</code>.<br>OR<br><code>value_type</code> is the exact same type as decayed <code>A</code> and <code>value_type</code> is implicitly constructible from <code>A</code>.</li>
- </ol></li>
- <li><p><code>predicate::enable_error_converting_constructor<A></code> is constexpr boolean true if:</p>
- <ol>
- <li><code>predicate::constructors_enabled</code> is true.</li>
- <li>Decayed <code>A</code> is not this <code>basic_result</code> type.</li>
- <li><code>predicate::implicit_constructors_enabled</code> is true.</li>
- <li>Decayed <code>A</code> is not an <code>in_place_type_t</code>.</li>
- <li>Trait <a href="../../reference/traits/is_error_type_enum.html" class="api-reference"><code>is_error_type_enum<E, Enum></code></a>
- is false for <code>error_type</code> and decayed <code>A</code>.</li>
- <li><code>value_type</code> is not implicitly constructible from <code>A</code> and <code>error_type</code> is implicitly constructible from <code>A</code>.<br>OR<br><code>error_type</code> is the exact same type as decayed <code>A</code> and <code>error_type</code> is implicitly constructible from <code>A</code>.</li>
- </ol></li>
- <li><p><code>predicate::enable_error_condition_converting_constructor<ErrorCondEnum></code> is constexpr boolean true if:</p>
- <ol>
- <li><code>predicate::constructors_enabled</code> is true.</li>
- <li>Decayed <code>ErrorCondEnum</code> is not this <code>basic_result</code> type.</li>
- <li>Decayed <code>ErrorCondEnum</code> is not an <code>in_place_type_t</code>.</li>
- <li>Trait <a href="../../reference/traits/is_error_type_enum.html" class="api-reference"><code>is_error_type_enum<E, Enum></code></a>
- is true for <code>error_type</code> and decayed <code>ErrorCondEnum</code>.</li>
- </ol></li>
- <li><p><code>predicate::enable_compatible_conversion<A, B, C></code> is constexpr boolean true if:</p>
- <ol>
- <li><code>predicate::constructors_enabled</code> is true.</li>
- <li><code>basic_result<A, B, C></code> is not this <code>basic_result</code> type.</li>
- <li><code>A</code> is <code>void</code> OR <code>value_type</code> is explicitly constructible from <code>A</code>.</li>
- <li><code>B</code> is <code>void</code> OR <code>error_type</code> is explicitly constructible from <code>B</code>.</li>
- </ol></li>
- <li><p><code>predicate::enable_make_error_code_compatible_conversion<A, B, C></code> is constexpr boolean true if:</p>
- <ol>
- <li><code>predicate::constructors_enabled</code> is true.</li>
- <li><code>basic_result<A, B, C></code> is not this <code>basic_result</code> type.</li>
- <li>Trait "/home/travis/build/ned14/boost-outcome/doc/src/content/reference/types/basic_result/_index.md:92:14": API reference page for 'is_error_code_available<E>' not found, please use an identifier wholly contained in a page title
- <b>API NOT FOUND IN DOCS <code>is_error_code_available<E></code></b>
- is true for decayed <code>error_type</code>.</li>
- <li><code>predicate::enable_compatible_conversion<A, B, C></code> is not true.</li>
- <li><code>A</code> is <code>void</code> OR <code>value_type</code> is explicitly constructible from <code>A</code>.</li>
- <li><code>error_type</code> is explicitly constructible from <code>make_error_code(B)</code>.</li>
- </ol></li>
- <li><p><code>predicate::enable_make_exception_ptr_compatible_conversion<A, B, C></code> is constexpr boolean true if:</p>
- <ol>
- <li><code>predicate::constructors_enabled</code> is true.</li>
- <li><code>basic_result<A, B, C></code> is not this <code>basic_result</code> type.</li>
- <li>Trait "/home/travis/build/ned14/boost-outcome/doc/src/content/reference/types/basic_result/_index.md:100:14": API reference page for 'is_exception_ptr_available<E>' not found, please use an identifier wholly contained in a page title
- <b>API NOT FOUND IN DOCS <code>is_exception_ptr_available<E></code></b>
- is true for decayed <code>error_type</code>.</li>
- <li><code>predicate::enable_compatible_conversion<A, B, C></code> is not true.</li>
- <li><code>A</code> is <code>void</code> OR <code>value_type</code> is explicitly constructible from <code>A</code>.</li>
- <li><code>error_type</code> is explicitly constructible from <code>make_exception_ptr(B)</code>.</li>
- </ol></li>
- <li><p><code>predicate::enable_inplace_value_constructor<Args...></code> is constexpr boolean true if:</p>
- <ol>
- <li><code>predicate::constructors_enabled</code> is true.</li>
- <li><code>value_type</code> is <code>void</code> OR <code>value_type</code> is explicitly constructible from <code>Args...</code>.</li>
- </ol></li>
- <li><p><code>predicate::enable_inplace_error_constructor<Args...></code> is constexpr boolean true if:</p>
- <ol>
- <li><code>predicate::constructors_enabled</code> is true.</li>
- <li><code>error_type</code> is <code>void</code> OR <code>error_type</code> is explicitly constructible from <code>Args...</code>.</li>
- </ol></li>
- <li><p><code>predicate::enable_inplace_value_error_constructor<Args...></code> is constexpr boolean true if:</p>
- <ol>
- <li><code>predicate::constructors_enabled</code> is true.</li>
- <li><code>predicate::implicit_constructors_enabled</code> is true.</li>
- <li>Either, but not both, of <code>value_type</code> is explicitly constructible from <code>Args...</code> or <code>error_type</code> is explicitly constructible from <code>Args...</code>.</li>
- </ol></li>
- </ul>
- <h4 id="summary-of-standard-requirements-provided-https-en-cppreference-com-w-cpp-named-req">Summary of <a href="https://en.cppreference.com/w/cpp/named_req">standard requirements provided</a></h4>
- <ul>
- <li><del><code>DefaultConstructible</code></del>, always deleted to force user to choose valued or errored for every result instanced.</li>
- <li><code>MoveConstructible</code>, if both <code>value_type</code> and <code>error_type</code> implement move constructors.</li>
- <li><code>CopyConstructible</code>, if both <code>value_type</code> and <code>error_type</code> implement copy constructors.</li>
- <li><code>MoveAssignable</code>, if both <code>value_type</code> and <code>error_type</code> implement move constructors and move assignment.</li>
- <li><code>CopyAssignable</code>, if both <code>value_type</code> and <code>error_type</code> implement copy constructors and copy assignment.</li>
- <li><code>Destructible</code>.</li>
- <li><code>TriviallyCopyable</code>, if both <code>value_type</code> and <code>error_type</code> are trivially copyable.</li>
- <li><code>TrivialType</code>, if both <code>value_type</code> and <code>error_type</code> are trivial types.</li>
- <li><code>LiteralType</code>, if both <code>value_type</code> and <code>error_type</code> are literal types.</li>
- <li><p><code>StandardLayoutType</code>, if both <code>value_type</code> and <code>error_type</code> are standard layout types. If so, layout of <code>basic_result</code> in C is guaranteed to be:</p>
- <div class="highlight"><pre class="chroma"><code class="language-c++" data-lang="c++"><span class="k">struct</span> <span class="n">result_layout</span> <span class="p">{</span>
- <span class="n">value_type</span> <span class="n">value</span><span class="p">;</span>
- <span class="kt">unsigned</span> <span class="kt">int</span> <span class="n">flags</span><span class="p">;</span>
- <span class="n">error_type</span> <span class="n">error</span><span class="p">;</span>
- <span class="p">};</span>
- </code></pre></div></li>
- <li><p><code>EqualityComparable</code>, if both <code>value_type</code> and <code>error_type</code> implement equality comparisons with one another.</p></li>
- <li><p><del><code>LessThanComparable</code></del>, not implemented due to availability of implicit conversions from <code>value_type</code> and <code>error_type</code>, this can cause major surprise (i.e. hard to diagnose bugs), so we don’t implement these at all.
- ~ <code>Swappable</code></p></li>
- <li><p><del><code>Hash</code></del>, not implemented as a generic implementation of a unique hash for non-valued items which are unequal would require a dependency on RTTI being enabled.</p></li>
- </ul>
- <p>Thus <code>basic_result</code> meets the <code>Regular</code> concept if both <code>value_type</code> and <code>error_type</code> are <code>Regular</code>, except for the lack of a default constructor. Often where one needs a default constructor, wrapping <code>basic_result</code> into
- <a href="https://en.cppreference.com/w/cpp/utility/optional" class="api-reference" target="_blank"><i class="fa fa-book" aria-hidden="true"></i> <code>std::optional<T></code></a>
- will suffice.</p>
- <h3 id="public-member-functions">Public member functions</h3>
- <h4 id="disabling-constructors">Disabling constructors</h4>
- <ol class="children children-li"><li>
- <a href="../../reference/types/basic_result/disabling_catchall.html" ><code>basic_result(Args...) = delete</code></a>
- <p>Disabling catchall constructor used to give useful diagnostic error when trying to use non-inplace constructors when <code>predicate::constructors_enabled</code> is false.</p><li>
- <a href="../../reference/types/basic_result/disabling_implicit_constructor.html" ><code>basic_result(X &&) = delete</code></a>
- <p>Disabling implicit constructor used to give useful diagnostic error when trying to use implicit constructors when <code>predicate::implicit_constructors_enabled</code> is false.</p></li></ol>
- <h4 id="copy-and-move-constructors-and-assignment-and-destructor">Copy and move constructors and assignment, and destructor</h4>
- <ol class="children children-li"><li>
- <a href="../../reference/types/basic_result/default.html" ><code>basic_result() = delete</code></a>
- <p>The default constructor (disabled).</p><li>
- <a href="../../reference/types/basic_result/move_constructor.html" ><code>basic_result(basic_result &&)</code></a>
- <p>Move constructor. Constexpr, triviality and noexcept propagating.</p><li>
- <a href="../../reference/types/basic_result/copy_constructor.html" ><code>basic_result(const basic_result &)</code></a>
- <p>Copy constructor. Constexpr, triviality and noexcept propagating.</p><li>
- <a href="../../reference/types/basic_result/move_assignment.html" ><code>basic_result &operator=(basic_result &&)</code></a>
- <p>Move assignment. Constexpr, triviality and noexcept propagating.</p><li>
- <a href="../../reference/types/basic_result/copy_assignment.html" ><code>basic_result &operator=(const basic_result &)</code></a>
- <p>Copy assignment. Constexpr, triviality and noexcept propagating.</p><li>
- <a href="../../reference/types/basic_result/destructor.html" ><code>~basic_result()</code></a>
- <p>Destructor. Constexpr, triviality and noexcept propagating.</p></li></ol>
- <h4 id="converting-constructors">Converting constructors</h4>
- <ol class="children children-li"><li>
- <a href="../../reference/types/basic_result/implicit_value_converting_constructor.html" ><code>basic_result(R &&)</code></a>
- <p>Implicit <code>value_type</code> constructor. Available if <code>predicate::enable_value_converting_constructor<R></code> is true. Constexpr, triviality and noexcept propagating.</p><li>
- <a href="../../reference/types/basic_result/implicit_error_converting_constructor.html" ><code>basic_result(S &&)</code></a>
- <p>Implicit <code>error_type</code> constructor. Available if <code>predicate::enable_error_converting_constructor<S></code> is true. Constexpr, triviality and noexcept propagating.</p><li>
- <a href="../../reference/types/basic_result/implicit_error_condition_converting_constructor.html" ><code>basic_result(ErrorCondEnum &&)</code></a>
- <p>Implicit <code>error_type</code> from <code>ErrorCondEnum</code> constructor. Available if <code>predicate::enable_error_condition_converting_constructor<ErrorCondEnum></code> is true. Constexpr, triviality and noexcept propagating.</p><li>
- <a href="../../reference/types/basic_result/explicit_valueorerror_converting_constructor.html" ><code>explicit basic_result(ValueOrError<T, E> &&)</code></a>
- <p>Explicit converting constructor from <code>ValueOrError<T, E></code> concept matching types. Available if <code>convert::value_or_error<></code> permits it. Constexpr, triviality and noexcept propagating.</p><li>
- <a href="../../reference/types/basic_result/explicit_copy_converting_constructor.html" ><code>explicit basic_result(const basic_result<R, S, P> &)</code></a>
- <p>Explicit converting copy constructor from compatible <code>basic_result</code>. Available if <code>predicate::enable_compatible_conversion<R, S, P></code> is true. Constexpr, triviality and noexcept propagating.</p><li>
- <a href="../../reference/types/basic_result/explicit_move_converting_constructor.html" ><code>explicit basic_result(basic_result<R, S, P> &&)</code></a>
- <p>Explicit converting move constructor from compatible <code>basic_result</code>. Available if <code>predicate::enable_compatible_conversion<R, S, P></code> is true. Constexpr, triviality and noexcept propagating.</p><li>
- <a href="../../reference/types/basic_result/explicit_make_error_code_copy_converting_constructor.html" ><code>explicit basic_result(const basic_result<R, S, P> &)</code></a>
- <p>Explicit converting copy constructor from compatible <code>basic_result</code>. Available if <code>predicate::enable_make_error_code_compatible_conversion<R, S, P></code> is true. Constexpr, triviality and noexcept propagating.</p><li>
- <a href="../../reference/types/basic_result/explicit_make_error_code_move_converting_constructor.html" ><code>explicit basic_result(basic_result<R, S, P> &&)</code></a>
- <p>Explicit converting move constructor from compatible <code>basic_result</code>. Available if <code>predicate::enable_make_error_code_compatible_conversion<R, S, P></code> is true. Constexpr, triviality and noexcept propagating.</p><li>
- <a href="../../reference/types/basic_result/explicit_make_exception_ptr_copy_converting_constructor.html" ><code>explicit basic_result(const basic_result<R, S, P> &)</code></a>
- <p>Explicit converting copy constructor from compatible <code>basic_result</code>. Available if <code>predicate::enable_make_exception_ptr_compatible_conversion<R, S, P></code> is true. Constexpr, triviality and noexcept propagating.</p><li>
- <a href="../../reference/types/basic_result/explicit_make_exception_ptr_move_converting_constructor.html" ><code>explicit basic_result(basic_result<R, S, P> &&)</code></a>
- <p>Explicit converting move constructor from compatible <code>basic_result</code>. Available if <code>predicate::enable_make_exception_ptr_compatible_conversion<R, S, P></code> is true. Constexpr, triviality and noexcept propagating.</p></li></ol>
- <h4 id="inplace-constructors">Inplace constructors</h4>
- <ol class="children children-li"><li>
- <a href="../../reference/types/basic_result/explicit_inplace_value_constructor.html" ><code>explicit basic_result(in_place_type_t<value_type_if_enabled>, Args ...)</code></a>
- <p>Explicit inplace value constructor. Available if <code>predicate::enable_inplace_value_constructor<Args ...></code> is true. Constexpr, triviality and noexcept propagating.</p><li>
- <a href="../../reference/types/basic_result/explicit_inplace_value_constructor_il.html" ><code>explicit basic_result(in_place_type_t<value_type_if_enabled>, std::initializer_list<U>, Args ...)</code></a>
- <p>Explicit inplace value constructor. Available if <code>predicate::enable_inplace_value_constructor<std::initializer_list<U>, Args ...></code> is true. Constexpr, triviality and noexcept propagating.</p><li>
- <a href="../../reference/types/basic_result/explicit_inplace_error_constructor.html" ><code>explicit basic_result(in_place_type_t<error_type_if_enabled>, Args ...)</code></a>
- <p>Explicit inplace error constructor. Available if <code>predicate::enable_inplace_error_constructor<Args ...></code> is true. Constexpr, triviality and noexcept propagating.</p><li>
- <a href="../../reference/types/basic_result/explicit_inplace_error_constructor_il.html" ><code>explicit basic_result(in_place_type_t<error_type_if_enabled>, std::initializer_list<U>, Args ...)</code></a>
- <p>Explicit inplace error constructor. Available if <code>predicate::enable_inplace_error_constructor<std::initializer_list<U>, Args ...></code> is true. Constexpr, triviality and noexcept propagating.</p><li>
- <a href="../../reference/types/basic_result/implicit_inplace_value_error_constructor.html" ><code>basic_result(A1 &&, A2 &&, Args ...)</code></a>
- <p>Implicit inplace value or error constructor. Available if <code>predicate::enable_inplace_value_error_constructor<A1, A2, Args ...></code> is true. Constexpr, triviality and noexcept propagating.</p></li></ol>
- <h4 id="tagged-constructors">Tagged constructors</h4>
- <ol class="children children-li"><li>
- <a href="../../reference/types/basic_result/implicit_success_copy_constructor.html" ><code>basic_result(const success_type<T> &)</code></a>
- <p>Implicit value-from-success-type-sugar copy constructor. Available if <code>predicate::enable_compatible_conversion<T, void, void></code> is true, or <code>T</code> is <code>void</code>. Constexpr, triviality and noexcept propagating.</p><li>
- <a href="../../reference/types/basic_result/implicit_success_move_constructor.html" ><code>basic_result(success_type<T> &&)</code></a>
- <p>Implicit value-from-success-type-sugar move constructor. Available if <code>predicate::enable_compatible_conversion<T, void, void></code> is true, or <code>T</code> is <code>void</code>. Constexpr, triviality and noexcept propagating.</p><li>
- <a href="../../reference/types/basic_result/implicit_failure_copy_constructor.html" ><code>basic_result(const failure_type<T> &)</code></a>
- <p>Implicit error-from-failure-type-sugar copy constructor. Available if <code>predicate::enable_compatible_conversion<void, T, void></code> is true, or <code>T</code> is <code>void</code>. Constexpr, triviality and noexcept propagating.</p><li>
- <a href="../../reference/types/basic_result/implicit_failure_move_constructor.html" ><code>basic_result(failure_type<T> &&)</code></a>
- <p>Implicit error-from-failure-type-sugar move constructor. Available if <code>predicate::enable_compatible_conversion<void, T, void></code> is true, or <code>T</code> is <code>void</code>. Constexpr, triviality and noexcept propagating.</p><li>
- <a href="../../reference/types/basic_result/implicit_failure_make_error_code_copy_constructor.html" ><code>basic_result(const failure_type<T> &)</code></a>
- <p>Implicit error-from-failure-type-sugar copy constructor. Available if <code>predicate::enable_make_error_code_compatible_conversion<void, T, void></code> is true, or <code>T</code> is <code>void</code>. Constexpr, triviality and noexcept propagating.</p><li>
- <a href="../../reference/types/basic_result/implicit_failure_make_error_code_move_constructor.html" ><code>basic_result(failure_type<T> &&)</code></a>
- <p>Implicit error-from-failure-type-sugar move constructor. Available if <code>predicate::enable_make_error_code_compatible_conversion<void, T, void></code> is true, or <code>T</code> is <code>void</code>. Constexpr, triviality and noexcept propagating.</p><li>
- <a href="../../reference/types/basic_result/implicit_failure_make_exception_ptr_copy_constructor.html" ><code>basic_result(const failure_type<T> &)</code></a>
- <p>Implicit error-from-failure-type-sugar copy constructor. Available if <code>predicate::enable_make_exception_ptr_compatible_conversion<void, T, void></code> is true, or <code>T</code> is <code>void</code>. Constexpr, triviality and noexcept propagating.</p><li>
- <a href="../../reference/types/basic_result/implicit_failure_make_exception_ptr_move_constructor.html" ><code>basic_result(failure_type<T> &&)</code></a>
- <p>Implicit error-from-failure-type-sugar move constructor. Available if <code>predicate::enable_make_exception_ptr_compatible_conversion<void, T, void></code> is true, or <code>T</code> is <code>void</code>. Constexpr, triviality and noexcept propagating.</p></li></ol>
- <h4 id="observers">Observers</h4>
- <ol class="children children-li"><li>
- <a href="../../reference/types/basic_result/operator_bool.html" ><code>explicit operator bool() const noexcept</code></a>
- <p>Returns true if a value is present. Constexpr, never throws.</p><li>
- <a href="../../reference/types/basic_result/has_value.html" ><code>bool has_value() const noexcept</code></a>
- <p>Returns true if a value is present. Constexpr, never throws.</p><li>
- <a href="../../reference/types/basic_result/has_error.html" ><code>bool has_error() const noexcept</code></a>
- <p>Returns true if an error is present. Constexpr, never throws.</p><li>
- <a href="../../reference/types/basic_result/has_exception.html" ><code>bool has_exception() const noexcept</code></a>
- <p>Always returns false for <code>basic_result</code>. Constexpr, never throws.</p><li>
- <a href="../../reference/types/basic_result/has_failure.html" ><code>bool has_failure() const noexcept</code></a>
- <p>Returns true if there is either an error or an exception. Constexpr, never throws.</p><li>
- <a href="../../reference/types/basic_result/has_lost_consistency.html" ><code>bool has_lost_consistency() const noexcept</code></a>
- <p>Returns true if a preceding swap involving this object failed to preserve the strong guarantee. Constexpr, never throws.</p><li>
- <a href="../../reference/types/basic_result/assume_value_lvalue.html" ><code>value_type &assume_value() & noexcept</code></a>
- <p>Narrow contract lvalue reference observer of any value present. Constexpr propagating, never throws.</p><li>
- <a href="../../reference/types/basic_result/assume_value_lvalue_const.html" ><code>const value_type &assume_value() const & noexcept</code></a>
- <p>Narrow contract const lvalue reference observer of any value present. Constexpr propagating, never throws.</p><li>
- <a href="../../reference/types/basic_result/assume_value_rvalue.html" ><code>value_type &&assume_value() && noexcept</code></a>
- <p>Narrow contract rvalue reference observer of any value present. Constexpr propagating, never throws.</p><li>
- <a href="../../reference/types/basic_result/assume_value_rvalue_const.html" ><code>const value_type &&assume_value() const && noexcept</code></a>
- <p>Narrow contract const rvalue reference observer of any value present. Constexpr propagating, never throws.</p><li>
- <a href="../../reference/types/basic_result/value_lvalue.html" ><code>value_type &value() &</code></a>
- <p>Wide contract lvalue reference observer of any value present. Constexpr propagating.</p><li>
- <a href="../../reference/types/basic_result/value_lvalue_const.html" ><code>const value_type &value() const &</code></a>
- <p>Wide contract const lvalue reference observer of any value present. Constexpr propagating.</p><li>
- <a href="../../reference/types/basic_result/value_rvalue.html" ><code>value_type &&value() &&</code></a>
- <p>Wide contract rvalue reference observer of any value present. Constexpr propagating.</p><li>
- <a href="../../reference/types/basic_result/value_rvalue_const.html" ><code>const value_type &&value() const &&</code></a>
- <p>Wide contract const rvalue reference observer of any value present. Constexpr propagating.</p><li>
- <a href="../../reference/types/basic_result/assume_error_lvalue.html" ><code>error_type &assume_error() & noexcept</code></a>
- <p>Narrow contract lvalue reference observer of the stored error. Constexpr propagating, never throws.</p><li>
- <a href="../../reference/types/basic_result/assume_error_lvalue_const.html" ><code>const error_type &assume_error() const & noexcept</code></a>
- <p>Narrow contract const lvalue reference observer of the stored error. Constexpr propagating, never throws.</p><li>
- <a href="../../reference/types/basic_result/assume_error_rvalue.html" ><code>error_type &&assume_error() && noexcept</code></a>
- <p>Narrow contract rvalue reference observer of the stored error. Constexpr propagating, never throws.</p><li>
- <a href="../../reference/types/basic_result/assume_error_rvalue_const.html" ><code>const error_type &&assume_error() const && noexcept</code></a>
- <p>Narrow contract const rvalue reference observer of the stored error. Constexpr propagating, never throws.</p><li>
- <a href="../../reference/types/basic_result/error_lvalue.html" ><code>error_type &error() &</code></a>
- <p>Wide contract lvalue reference observer of the stored error. Constexpr propagating.</p><li>
- <a href="../../reference/types/basic_result/error_lvalue_const.html" ><code>const error_type &error() const &</code></a>
- <p>Wide contract const lvalue reference observer of the stored error. Constexpr propagating.</p><li>
- <a href="../../reference/types/basic_result/error_rvalue.html" ><code>error_type &&error() &&</code></a>
- <p>Wide contract rvalue reference observer of the stored error. Constexpr propagating.</p><li>
- <a href="../../reference/types/basic_result/error_rvalue_const.html" ><code>const error_type &&error() const &&</code></a>
- <p>Wide contract const rvalue reference observer of the stored error. Constexpr propagating.</p><li>
- <a href="../../reference/types/basic_result/as_failure_lvalue.html" ><code>auto as_failure() const &</code></a>
- <p>Return the output from free function <code>failure()</code> containing a copy of any errored state.</p></li></ol>
- <h4 id="modifiers">Modifiers</h4>
- <ol class="children children-li"><li>
- <a href="../../reference/types/basic_result/swap.html" ><code>void swap(basic_result &)</code></a>
- <p>Swap one basic_result with another, with the strong guarantee. Noexcept propagating.</p><li>
- <a href="../../reference/types/basic_result/as_failure_rvalue.html" ><code>auto as_failure() &&</code></a>
- <p>Return the output from free function <code>failure()</code> containing a move of any errored state.</p></li></ol>
- <h4 id="comparisons">Comparisons</h4>
- <p>See above for why <code>LessThanComparable</code> is not implemented.</p>
- <ol class="children children-li"><li>
- <a href="../../reference/types/basic_result/equality_basic_result.html" ><code>bool operator==(const basic_result<A, B, C> &) const</code></a>
- <p>Returns true if this result compares equal to the other result. Constexpr and noexcept propagating.</p><li>
- <a href="../../reference/types/basic_result/inequality_success_type.html" ><code>bool operator==(const success_type<A> &) const</code></a>
- <p>Returns true if this result compares equal to the success type sugar. Constexpr and noexcept propagating.</p><li>
- <a href="../../reference/types/basic_result/equality_failure_type.html" ><code>bool operator==(const failure_type<A, void> &) const</code></a>
- <p>Returns true if this result compares equal to the failure type sugar. Constexpr and noexcept propagating.</p><li>
- <a href="../../reference/types/basic_result/inequality_basic_result.html" ><code>bool operator!=(const basic_result<A, B, C> &) const</code></a>
- <p>Returns true if this result does not compare equal to the other result. Constexpr and noexcept propagating.</p><li>
- <a href="../../reference/types/basic_result/equality_success_type.html" ><code>bool operator!=(const success_type<A> &) const</code></a>
- <p>Returns true if this result does not compare equal to the success type sugar. Constexpr and noexcept propagating.</p><li>
- <a href="../../reference/types/basic_result/inequality_failure_type.html" ><code>bool operator!=(const failure_type<A, void> &) const</code></a>
- <p>Returns true if this result does not compare equal to the failure type sugar. Constexpr and noexcept propagating.</p></li></ol>
- </div><p><small>Last revised: October 11, 2019 at 17:03:05 +0100</small></p>
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