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Cleaner handling of explicit U to T conversions

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This commit is contained in:
Andrzej Krzemienski
2014-06-20 11:38:57 +02:00
parent 4af83ecf83
commit 4cbb67e505
5 changed files with 68 additions and 83 deletions
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doc/20_reference.qbk
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@ -326,7 +326,7 @@ __SPACE__
value is another reference to the same object referenced by `*rhs`; else
`*this` is uninitialized.
* [*Throws:] Nothing.
* [*Notes:] If `rhs` is initialized, both `*this` and `*rhs` will reefer to the
* [*Notes:] If `rhs` is initialized, both `*this` and `*rhs` will refer to the
same object (they alias).
* [*Example:]
``
@ -360,7 +360,8 @@ __SPACE__
* [*Postconditions:] If `rhs` is initialized, `*this` is initialized and
its value is move constructed from `rhs`; else `*this` is uninitialized.
* [*Throws:] Whatever `T::T( T&& )` throws.
* [*Notes:] If `rhs` is initialized, `T::T( T && )` is called. The expression inside `noexcept` is equivalent to `is_nothrow_move_constructible<T>::value`.
* [*Remarks:] The expression inside `noexcept` is equivalent to `is_nothrow_move_constructible<T>::value`.
* [*Notes:] If `rhs` is initialized, `T::T( T && )` is called.
* [*Exception Safety:] Exceptions can only be thrown during
`T::T( T&& );` in that case, `rhs` remains initialized and the value of `*rhs` is determined by exception safety of `T::T(T&&)`.
* [*Example:]
@ -390,7 +391,7 @@ __SPACE__
value is another reference to the same object referenced by `*rhs`; else
`*this` is uninitialized.
* [*Throws:] Nothing.
* [*Notes:] If `rhs` is initialized, both `*this` and `*rhs` will reefer to the
* [*Notes:] If `rhs` is initialized, both `*this` and `*rhs` will refer to the
same object (they alias).
* [*Example:]
``
@ -663,11 +664,12 @@ __SPACE__
* [*Effect:] Move-assigns another `optional` to an `optional`.
* [*Postconditions:] If `rhs` is initialized, `*this` is initialized and
its value is moved from `*rhs`, `rhs` remains initialized; else `*this` is uninitialized.
* [*Throws:] Whatever `T::operator( T&& )` or `T::T( T && )` throws.
* [*Throws:] Whatever `T::operator( T&& )` or `T::T( T && )` throws.
* [*Remarks:] The expression inside `noexcept` is equivalent to `is_nothrow_move_constructible<T>::value && is_nothrow_move_assignable<T>::value`.
* [*Notes:] If both `*this` and `rhs` are initially initialized, `T`'s
['move assignment operator] is used. If `*this` is initially initialized but `rhs` is
uninitialized, `T`'s [destructor] is called. If `*this` is initially uninitialized
but `rhs` is initialized, `T`'s ['move constructor] is called. The expression inside `noexcept` is equivalent to `is_nothrow_move_constructible<T>::value && is_nothrow_move_assignable<T>::value`.
but `rhs` is initialized, `T`'s ['move constructor] is called.
* [*Exception Safety:] In the event of an exception, the initialization state of
`*this` is unchanged and its value unspecified as far as optional is concerned
(it is up to `T`'s `operator=()`). If `*this` is initially uninitialized and
@ -932,8 +934,7 @@ __SPACE__
[: `template<class U> T optional<T>::value_or(U && v) const& ;`]
* [*Requires:] `T` is __COPY_CONSTRUCTIBLE__ and `U &&` is convertible to `T`.
* [*Returns:] `bool(*this) ? **this : static_cast<T>(std::forward<U>(v))`.
* [*Throws:] Any exception thrown by the selected constructor of `T`.
* [*Effects:] `if (*this) return **this; else return std::forward<U>(v);`.
* [*Notes:] On compilers that do not support ref-qualifiers on member functions this overload is replaced with the `const`-qualified member function. On compilers without rvalue reference support the type of `v` becomes `U const&`.
__SPACE__
@ -943,8 +944,7 @@ __SPACE__
[: `template<class U> T optional<T>::value_or(U && v) && ;`]
* [*Requires:] `T` is __MOVE_CONSTRUCTIBLE__ and `U &&` is convertible to `T`.
* [*Returns:] `bool(*this) ? std::move(**this) : static_cast<T>(std::forward<U>(v))`.
* [*Throws:] Any exception thrown by the selected constructor of `T`.
* [*Effects:] `if (*this) return std::move(**this); else return std::forward<U>(v);`.
* [*Notes:] On compilers that do not support ref-qualifiers on member functions this overload is not present.
__SPACE__
@ -954,9 +954,8 @@ __SPACE__
[: `template<class F> T optional<T>::value_or_eval(F f) const& ;`]
* [*Requires:] `T` is __COPY_CONSTRUCTIBLE__ and `F` models a __SGI_GENERATOR__ whose result type is convertible to `T`.
* [*Returns:] `bool(*this) ? **this : static_cast<T>(f())`.
* [*Throws:] Any exception thrown by the selected constructor of `T` or by `f`.
* [*Notes:] Function `f` is only evaluated if `bool(*this) == false`. On compilers that do not support ref-qualifiers on member functions this overload is replaced with the `const`-qualified member function.
* [*Effects:] `if (*this) return **this; else return f();`.
* [*Notes:] On compilers that do not support ref-qualifiers on member functions this overload is replaced with the `const`-qualified member function.
* [*Example:]
``
int complain_and_0()
@ -982,9 +981,8 @@ __SPACE__
[: `template<class F> T optional<T>::value_or_eval(F f) && ;`]
* [*Requires:] `T` is __MOVE_CONSTRUCTIBLE__ and `F` models a __SGI_GENERATOR__ whose result type is convertible to `T`.
* [*Returns:] `bool(*this) ? std::move(**this) : static_cast<T>(f())`.
* [*Throws:] Any exception thrown by the selected constructor of `T` or by `f`.
* [*Notes:] Function `f` is only evaluated if `bool(*this) == false`. On compilers that do not support ref-qualifiers on member functions this overload is not present.
* [*Effects:] `if (*this) return std::move(**this); else return f();`.
* [*Notes:] On compilers that do not support ref-qualifiers on member functions this overload is not present.
__SPACE__