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[INVOKE] added is_invocable_r, invoke_r, made everything constexpr and conditionally noexcept (#2458)
* - added dlib::invoke_r() - added dlib::is_invocable_r<> - made everything constexpr and conditionally noexcept ! - added tests This has required a refactor of dlib::invoke since std::mem_fn is not constexpr in c++11 * - !std::is_function replaced with std::is_object. Let's be a bit more precise * - made dlib::apply constexpr and conditionally noexcept Co-authored-by: pf <pf@me>
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pfeatherstone
GitHub
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1925b2d10f
176
dlib/invoke.h
176
dlib/invoke.h
@ -11,32 +11,153 @@ namespace dlib
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{
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// ----------------------------------------------------------------------------------------
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namespace detail {
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template< typename F, typename ... Args >
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auto INVOKE(F&& fn, Args&& ... args)
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template< typename T >
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struct is_reference_wrapper : std::false_type {};
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template< typename U >
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struct is_reference_wrapper<std::reference_wrapper<U>> : std::true_type {};
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template <
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typename Base,
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typename T,
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typename Derived,
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typename... Args
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>
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constexpr auto INVOKE(
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T Base::*pmf, //pointer to member function
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Derived&& ref,
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Args&&... args
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)
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noexcept(noexcept((std::forward<Derived>(ref).*pmf)(std::forward<Args>(args)...)))
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-> typename std::enable_if<
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std::is_member_pointer<typename std::decay<F>::type>::value,
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decltype(std::mem_fn(fn)(std::forward<Args>(args)...))>::type
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std::is_function<T>::value &&
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std::is_base_of<Base, typename std::decay<Derived>::type>::value,
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decltype((std::forward<Derived>(ref).*pmf)(std::forward<Args>(args)...))
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>::type
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{
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return std::mem_fn(fn)(std::forward<Args>(args)...) ;
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return (std::forward<Derived>(ref).*pmf)(std::forward<Args>(args)...);
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}
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template< typename F, typename ... Args >
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auto INVOKE(F&& fn, Args&& ... args)
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template<
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typename Base,
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typename T,
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typename RefWrap,
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typename... Args
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>
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constexpr auto INVOKE(
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T Base::*pmf, //pointer to member function
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RefWrap&& ref,
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Args&&... args
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)
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noexcept(noexcept((ref.get().*pmf)(std::forward<Args>(args)...)))
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-> typename std::enable_if<
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std::is_function<T>::value &&
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is_reference_wrapper<typename std::decay<RefWrap>::type>::value,
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decltype((ref.get().*pmf)(std::forward<Args>(args)...))>::type
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{
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return (ref.get().*pmf)(std::forward<Args>(args)...);
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}
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template<
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typename Base,
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typename T,
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typename Ptr,
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typename... Args
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>
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constexpr auto INVOKE(
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T Base::*pmf, //pointer to member function
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Ptr&& ptr,
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Args&&... args
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)
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noexcept(noexcept(((*std::forward<Ptr>(ptr)).*pmf)( std::forward<Args>( args )...)))
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-> typename std::enable_if<
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std::is_function<T>::value &&
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!is_reference_wrapper<typename std::decay<Ptr>::type>::value &&
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!std::is_base_of<Base, typename std::decay<Ptr>::type>::value,
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decltype(((*std::forward<Ptr>(ptr)).*pmf)(std::forward<Args>(args)...))>::type
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{
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return ((*std::forward<Ptr>(ptr)).*pmf)( std::forward<Args>( args )...);
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}
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template<
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typename Base,
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typename T,
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typename Derived
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>
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constexpr auto INVOKE(
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T Base::*pmd, //pointer to member data
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Derived&& ref
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)
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noexcept(noexcept(std::forward<Derived>(ref).*pmd))
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-> typename std::enable_if<
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std::is_object<T>::value &&
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std::is_base_of<Base, typename std::decay<Derived>::type>::value,
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decltype(std::forward<Derived>(ref).*pmd)>::type
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{
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return std::forward<Derived>(ref).*pmd;
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}
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template<
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typename Base,
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typename T,
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typename RefWrap
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>
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constexpr auto INVOKE(
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T Base::*pmd, //pointer to member data
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RefWrap&& ref
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)
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noexcept(noexcept(ref.get().*pmd))
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-> typename std::enable_if<
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std::is_object<T>::value &&
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is_reference_wrapper<typename std::decay<RefWrap>::type>::value,
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decltype(ref.get().*pmd)>::type
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{
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return ref.get().*pmd;
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}
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template<
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typename Base,
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typename T,
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typename Ptr
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>
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constexpr auto INVOKE(
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T Base::*pmd, //pointer to member data
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Ptr&& ptr
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)
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noexcept(noexcept((*std::forward<Ptr>(ptr)).*pmd))
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-> typename std::enable_if<
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std::is_object<T>::value &&
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!is_reference_wrapper<typename std::decay<Ptr>::type>::value &&
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!std::is_base_of<Base, typename std::decay<Ptr>::type>::value,
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decltype((*std::forward<Ptr>(ptr)).*pmd)>::type
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{
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return (*std::forward<Ptr>(ptr)).*pmd;
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}
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template<
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typename F,
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typename... Args
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>
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constexpr auto INVOKE(
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F && f,
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Args&&... args
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)
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noexcept(noexcept(std::forward<F>( f )( std::forward<Args>( args )...)))
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-> typename std::enable_if<
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!std::is_member_pointer<typename std::decay<F>::type>::value,
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decltype(std::forward<F>(fn)(std::forward<Args>(args)...))>::type
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decltype(std::forward<F>(f)(std::forward<Args>(args)...))>::type
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{
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return std::forward<F>(fn)(std::forward<Args>(args)...);
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return std::forward<F>( f )( std::forward<Args>( args )...);
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}
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}
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template< typename F, typename... Args>
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auto invoke(F && f, Args &&... args)
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constexpr auto invoke(F && f, Args &&... args)
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/*!
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ensures
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- identical to std::invoke(std::forward<F>(f), std::forward<Args>(args)...)
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- works with C++11 onwards
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!*/
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noexcept(noexcept(detail::INVOKE(std::forward<F>( f ), std::forward<Args>( args )...)))
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-> decltype(detail::INVOKE(std::forward<F>( f ), std::forward<Args>( args )...))
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{
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return detail::INVOKE(std::forward<F>( f ), std::forward<Args>( args )...);
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@ -88,10 +209,38 @@ namespace dlib
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// ----------------------------------------------------------------------------------------
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template <typename R, typename F, typename... Args>
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struct is_invocable_r : std::integral_constant<bool, dlib::is_invocable<F, Args...>::value &&
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std::is_convertible<invoke_result_t<F, Args...>, R>::value> {};
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/*!
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ensures
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- identical to std::is_invocable_r<R, F, Args..>
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- works with C++11 onwards
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!*/
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// ----------------------------------------------------------------------------------------
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template< typename R, typename F, typename... Args>
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constexpr typename std::enable_if<dlib::is_invocable_r<R, F, Args...>::value, R>::type
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invoke_r(F && f, Args &&... args)
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/*!
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ensures
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- identical to std::invoke_r<R>(std::forward<F>(f), std::forward<Args>(args)...)
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- works with C++11 onwards
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!*/
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noexcept(noexcept(dlib::invoke(std::forward<F>( f ), std::forward<Args>( args )...)))
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{
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return dlib::invoke(std::forward<F>( f ), std::forward<Args>( args )...);
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}
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// ----------------------------------------------------------------------------------------
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namespace detail
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{
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template<typename F, typename Tuple, std::size_t... I>
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auto apply_impl(F&& fn, Tuple&& tpl, index_sequence<I...>)
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constexpr auto apply_impl(F&& fn, Tuple&& tpl, index_sequence<I...>)
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noexcept(noexcept(dlib::invoke(std::forward<F>(fn),
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std::get<I>(std::forward<Tuple>(tpl))...)))
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-> decltype(dlib::invoke(std::forward<F>(fn),
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std::get<I>(std::forward<Tuple>(tpl))...))
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{
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@ -101,12 +250,15 @@ namespace dlib
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}
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template<typename F, typename Tuple>
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auto apply(F&& fn, Tuple&& tpl)
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constexpr auto apply(F&& fn, Tuple&& tpl)
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/*!
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ensures
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- identical to std::apply(std::forward<F>(f), std::forward<Tuple>(tpl))
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- works with C++11 onwards
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!*/
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noexcept(noexcept(detail::apply_impl(std::forward<F>(fn),
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std::forward<Tuple>(tpl),
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make_index_sequence<std::tuple_size<typename std::remove_reference<Tuple>::type >::value>{})))
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-> decltype(detail::apply_impl(std::forward<F>(fn),
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std::forward<Tuple>(tpl),
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make_index_sequence<std::tuple_size<typename std::remove_reference<Tuple>::type >::value>{}))
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@ -234,6 +234,100 @@ namespace
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// ----------------------------------------------------------------------------------------
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const char* func_return_c_string()
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{
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return "hello darkness my old friend";
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}
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struct obj_return_c_string
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{
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obj_return_c_string() = default;
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obj_return_c_string(const obj_return_c_string& rhs) = delete;
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obj_return_c_string(obj_return_c_string&& rhs) = delete;
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const char* run()
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{
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return "i've come to talk with you again";
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}
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};
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void test_invoke_r()
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{
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{
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static_assert(dlib::is_invocable_r<std::string, decltype(func_return_c_string)>::value, "should be invocable");
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auto str = dlib::invoke_r<std::string>(func_return_c_string);
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static_assert(std::is_same<decltype(str), std::string>::value, "bad return type");
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DLIB_TEST(str == "hello darkness my old friend");
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}
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{
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obj_return_c_string obj;
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static_assert(dlib::is_invocable_r<std::string, decltype(&obj_return_c_string::run), decltype(obj)>::value, "should be invocable");
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auto str = dlib::invoke_r<std::string>(&obj_return_c_string::run, obj);
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static_assert(std::is_same<decltype(str), std::string>::value, "bad return type");
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DLIB_TEST(str == "i've come to talk with you again");
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}
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{
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obj_return_c_string obj;
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static_assert(dlib::is_invocable_r<std::string, decltype(&obj_return_c_string::run), decltype(&obj)>::value, "should be invocable");
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auto str = dlib::invoke_r<std::string>(&obj_return_c_string::run, &obj);
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static_assert(std::is_same<decltype(str), std::string>::value, "bad return type");
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DLIB_TEST(str == "i've come to talk with you again");
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}
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{
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auto obj = std::make_shared<obj_return_c_string>();
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static_assert(dlib::is_invocable_r<std::string, decltype(&obj_return_c_string::run), decltype(obj)>::value, "should be invocable");
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auto str = dlib::invoke_r<std::string>(&obj_return_c_string::run, obj);
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static_assert(std::is_same<decltype(str), std::string>::value, "bad return type");
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DLIB_TEST(str == "i've come to talk with you again");
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}
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{
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std::unique_ptr<obj_return_c_string> obj(new obj_return_c_string());
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static_assert(dlib::is_invocable_r<std::string, decltype(&obj_return_c_string::run), decltype(obj)>::value, "should be invocable");
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auto str = dlib::invoke_r<std::string>(&obj_return_c_string::run, obj);
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static_assert(std::is_same<decltype(str), std::string>::value, "bad return type");
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DLIB_TEST(str == "i've come to talk with you again");
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}
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{
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auto lambda_return_c_string = [] {
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return "because a vision softly creeping";
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};
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static_assert(dlib::is_invocable_r<std::string, decltype(lambda_return_c_string)>::value, "should be invocable");
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auto str = dlib::invoke_r<std::string>(lambda_return_c_string);
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static_assert(std::is_same<decltype(str), std::string>::value, "bad return type");
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DLIB_TEST(str == "because a vision softly creeping");
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}
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}
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// ----------------------------------------------------------------------------------------
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constexpr int multiply_ints(int i, int j)
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{
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return i*j;
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}
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struct constexpr_object
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{
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constexpr int multiply_ints(int i, int j) const
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{
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return i*j;
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}
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};
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void test_constexpr()
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{
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static_assert(dlib::invoke(multiply_ints, 2, 5) == 10, "this should be constexpr");
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static_assert(dlib::invoke_r<long>(multiply_ints, 2, 5) == 10, "this should be constexpr");
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constexpr constexpr_object constexpr_obj;
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static_assert(dlib::invoke(&constexpr_object::multiply_ints, constexpr_obj, 2, 5) == 10);
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static_assert(dlib::invoke_r<long>(&constexpr_object::multiply_ints, constexpr_obj, 2, 5) == 10);
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}
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// ----------------------------------------------------------------------------------------
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class invoke_tester : public tester
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{
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@ -251,6 +345,8 @@ namespace
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test_member_functions_and_data();
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test_return_types();
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test_make_from_tuple();
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test_invoke_r();
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test_constexpr();
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}
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} a;
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}
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