std::function_ref::function_ref

 

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Utilities library

Language support Type support (basic types, RTTI) Library feature-test macros (C++20) Dynamic memory management Program utilities Coroutine support (C++20) Variadic functions is_constant_evaluated (C++20) is_within_lifetime (C++26) initializer_list (C++11) source_location (C++20) Three-way comparison three_way_comparablethree_way_comparable_with (C++20)(C++20) strong_ordering (C++20) weak_ordering (C++20) partial_ordering (C++20) common_comparison_category (C++20) compare_three_way_result (C++20) compare_three_way (C++20) strong_order (C++20) weak_order (C++20) partial_order (C++20) compare_strong_order_fallback (C++20) compare_weak_order_fallback (C++20) compare_partial_order_fallback (C++20)   is_eqis_ltis_lteq (C++20)(C++20)(C++20)   is_neqis_gtis_gteq (C++20)(C++20)(C++20)

General utilities Date and time Function objects Formatting library (C++20)   bitset hash (C++11) Relational operators (deprecated in C++20) rel_ops::operator!=rel_ops::operator>    rel_ops::operator<=rel_ops::operator>= Integer comparison functions cmp_equalcmp_lesscmp_less_than (C++20)(C++20)(C++20)   cmp_not_equalcmp_greatercmp_greater_than (C++20)(C++20)(C++20) in_range (C++20) Swap and type operations swap ranges::swap (C++20) exchange (C++14) declval (C++11) to_underlying (C++23) forward (C++11) forward_like (C++23) move (C++11) move_if_noexcept (C++11) as_const (C++17) Common vocabulary types pair tuple (C++11) optional (C++17) any (C++17) variant (C++17) tuple_size (C++11) tuple_element (C++11) apply (C++17) make_from_tuple (C++17) expected (C++23) Elementary string conversions to_chars (C++17) from_chars (C++17) chars_format (C++17) to_chars_result (C++17) from_chars_result (C++17)

 

Function objects

Function wrappers function (C++11) move_only_function (C++23) copyable_function (C++26) function_ref (C++26) mem_fn (C++11) bad_function_call (C++11)	Partial function application bind_frontbind_back (C++20)(C++23) bind (C++11) is_bind_expression (C++11) is_placeholder (C++11) _1, _2, _3, ... (C++11)
Function invocation invokeinvoke_r (C++17)(C++23) Identity function object identity (C++20)	Reference wrappers reference_wrapper (C++11) refcref (C++11)(C++11) unwrap_referenceunwrap_ref_decay (C++20)(C++20)
Operator wrappers plus minus negate multiplies divides modulus bit_and bit_or bit_not (C++14)   bit_xor equal_to not_equal_to greater less greater_equal less_equal logical_and logical_or logical_not	Transparent operator wrappers plus<> (C++14) minus<> (C++14) negate<> (C++14) multiplies<> (C++14)   divides<> (C++14) modulus<> (C++14) bit_and<> (C++14) bit_or<> (C++14) bit_not<> (C++14) bit_xor<> (C++14) equal_to<> (C++14) not_equal_to<> (C++14) greater<> (C++14) less<> (C++14) greater_equal<> (C++14) less_equal<> (C++14) logical_and<> (C++14) logical_or<> (C++14) logical_not<> (C++14)
Negators not_fn (C++17) Searchers default_searcher (C++17) boyer_moore_searcher (C++17) boyer_moore_horspool_searcher (C++17)	Constrained comparators ranges::equal_to (C++20) ranges::not_equal_to (C++20) ranges::greater (C++20) ranges::less (C++20) ranges::greater_equal (C++20) ranges::less_equal (C++20) compare_three_way (C++20)
Old binders and adaptors
unary_function (until C++17*) binary_function (until C++17*) ptr_fun (until C++17*) pointer_to_unary_function (until C++17*) pointer_to_binary_function (until C++17*)   mem_fun (until C++17*) mem_fun_tmem_fun1_tconst_mem_fun_tconst_mem_fun1_t (until C++17*)(until C++17*)(until C++17*)(until C++17*) not1 (until C++20*) not2 (until C++20*)	binder1stbinder2nd (until C++17*)(until C++17*) bind1stbind2nd (until C++17*)(until C++17*) mem_fun_ref (until C++17*) mem_fun_ref_tmem_fun1_ref_tconst_mem_fun_ref_tconst_mem_fun1_ref_t (until C++17*)(until C++17*)(until C++17*)(until C++17*) unary_negate (until C++20*) binary_negate (until C++20*)

 

std::function_ref

Member functions

function_ref::function_ref

function_ref::operator=

function_ref::operator()

Deduction guides

 

template< class F > function_ref( F* f ) noexcept;	(1)	(since C++26)
template< class F > function_ref( F&& f ) noexcept;	(2)	(since C++26)
template< auto f > function_ref( std::nontype_t<f> ) noexcept;	(3)	(since C++26)
template< auto f, class U > function_ref( std::nontype_t<f>, U&& obj ) noexcept;	(4)	(since C++26)
template< auto f, class T > function_ref( std::nontype_t<f>, /*cv*/ T* obj ) noexcept;	(5)	(since C++26)
function_ref( const function_ref& other ) = default;	(6)	(since C++26)

Creates a new std::function_ref.

1) Initializes bound-entity with f, and thunk-ptr with the address of a function thunk. The behavior is undefined if f is a null pointer.

• This overload participates in overload resolution only if both std::is_function_v<F> and /*is-invocable-using*/<F> are true.

2) Initializes bound-entity with std::addressof(f), and thunk-ptr with the address of a function thunk.

• Let T be std::remove_reference_t<F>. This overload participates in overload resolution only if :
  • std::remove_cvref_t<F> is not the same type as function_ref,
  • std::is_member_pointer_v<T> is false, and
  • /*is-invocable-using*/</*cv*/ T&> is true.

3) Initializes bound-entity with a pointer to an unspecified object or null pointer value, and thunk-ptr with the address of a function thunk.

• Let F be decltype(f). This overload participates in overload resolution only if /*is-invocable-using*/<F> is true.
• The program is ill-formed if f != nullptr is false when std::is_pointer_v<F> || std::is_member_pointer_v<F> is true.

4) Initializes bound-entity with std::addressof(obj), and thunk-ptr with the address of a function thunk.

• Let T be std::remove_reference_t<U> and F be decltype(f). This overload participates in overload resolution only if :
  • std::is_rvalue_reference_v<U&&> is false, and
  • /*is-invocable-using*/<F, /*cv*/ T&> is true.
• The program is ill-formed if f != nullptr is false when std::is_pointer_v<F> || std::is_member_pointer_v<F> is true.

5) Initializes bound-entity with obj, and thunk-ptr with the address of a function thunk. The behavior is undefined if obj is a null pointer when std::is_member_pointer_v<F> is true.

• Let F be decltype(f). This overload participates in overload resolution only if /*is-invocable-using*/<F, /*cv*/ T*> is true.
• The program is ill-formed if f != nullptr is false when std::is_pointer_v<F> || std::is_member_pointer_v<F> is true.

6) Defaulted copy constructor copies the bound-entity and thunk-ptr of other.

The address of a function thunk is used to initialize thunk-ptr such that a call to thunk(bound-entity, call-args...) is expression-equivalent to:

Overloads	Expression-equivalence
(1,3)	std::invoke_r<R>(f, call-args...)
(2)	std::invoke_r<R>(static_cast<cv T&>(f), call-args...)
(4)	std::invoke_r<R>(f, static_cast<cv T&>(obj), call-args...)
(5)	std::invoke_r<R>(f, obj, call-args...)

/*is-invocable-using*/<T...> is true if and only if:

• std::is_nothrow_invocable_r_v<R, T..., Args...> is true if noex is true, or
• std::is_invocable_r_v<R, T..., Args...> is true

Parameters

other	-	another function_ref to copy from
f	-	a function or a Callable object to wrap
obj	-	an object or pointer to bound

See also

(constructor)

constructs a new std::move_only_function object (public member function of std::move_only_function)