20 General utilities library [utilities]

20.14 Function objects [function.objects]

20.14.10 Function object binders [func.bind]

20.14.10.3 Function template bind [func.bind.bind]

1

In the text that follows:

  • (1.1)

    FD is the type decay_t<F>,

  • (1.2)

    fd is an lvalue of type FD constructed from std::forward<F>(f),

  • (1.3)

    Ti is the ith type in the template parameter pack BoundArgs,

  • (1.4)

    TiD is the type decay_t<Ti>,

  • (1.5)

    ti is the ith argument in the function parameter pack bound_args,

  • (1.6)

    tid is an lvalue of type TiD constructed from std::forward<Ti>(ti),

  • (1.7)

    Uj is the jth deduced type of the UnBoundArgs&&... parameter of the forwarding call wrapper, and

  • (1.8)

    uj is the jth argument associated with Uj.

template<class F, class... BoundArgs> unspecified bind(F&& f, BoundArgs&&... bound_args);

2

Requires: is_constructible_v<FD, F> shall be true. For each Ti in BoundArgs, is_constructible_v<TiD, Ti> shall be true. INVOKE (fd, w1, w2, ..., wN) ([func.require]) shall be a valid expression for some values w1, w2, ..., wN, where N == sizeof...(bound_args). The cv-qualifiers cv of the call wrapper g, as specified below, shall be neither volatile nor const volatile.

3

Returns: A forwarding call wrapper g ([func.require]). The effect of g(u1, u2, ..., uM) shall be INVOKE(fd, std::forward<V1>(v1), std::forward<V2>(v2), ..., std::forward<VN>(vN)), where the values and types of the bound arguments v1, v2, ..., vN are determined as specified below. The copy constructor and move constructor of the forwarding call wrapper shall throw an exception if and only if the corresponding constructor of FD or of any of the types TiD throws an exception.

4

Throws: Nothing unless the construction of fd or of one of the values tid throws an exception.

5

Remarks: The return type shall satisfy the requirements of MoveConstructible. If all of FD and TiD satisfy the requirements of CopyConstructible, then the return type shall satisfy the requirements of CopyConstructible. [ Note: This implies that all of FD and TiD are MoveConstructible.  — end note ]

template<class R, class F, class... BoundArgs> unspecified bind(F&& f, BoundArgs&&... bound_args);

6

Requires: is_constructible_v<FD, F> shall be true. For each Ti in BoundArgs, is_constructible_v<TiD, Ti> shall be true. INVOKE(fd, w1, w2, ..., wN) shall be a valid expression for some values w1, w2, ..., wN, where N == sizeof...(bound_args). The cv-qualifiers cv of the call wrapper g, as specified below, shall be neither volatile nor const volatile.

7

Returns: A forwarding call wrapper g ([func.require]). The effect of g(u1, u2, ..., uM) shall be INVOKE(fd, std::forward<V1>(v1), std::forward<V2>(v2), ..., std::forward<VN>(vN), R), where the values and types of the bound arguments v1, v2, ..., vN are determined as specified below. The copy constructor and move constructor of the forwarding call wrapper shall throw an exception if and only if the corresponding constructor of FD or of any of the types TiD throws an exception.

8

Throws: Nothing unless the construction of fd or of one of the values tid throws an exception.

9

Remarks: The return type shall satisfy the requirements of MoveConstructible. If all of FD and TiD satisfy the requirements of CopyConstructible, then the return type shall satisfy the requirements of CopyConstructible. [ Note: This implies that all of FD and TiD are MoveConstructible.  — end note ]

10

The values of the bound arguments v1, v2, ..., vN and their corresponding types V1, V2, ..., VN depend on the types TiD derived from the call to bind and the cv-qualifiers cv of the call wrapper g as follows:

  • (10.1)

    if TiD is reference_wrapper<T>, the argument is tid.get() and its type Vi is T&;

  • (10.2)

    if the value of is_bind_expression_v<TiD> is true, the argument is tid(std::forward<Uj>(uj)...) and its type Vi is result_of_t<TiD cv & (Uj&&...)>&&;

  • (10.3)

    if the value j of is_placeholder_v<TiD> is not zero, the argument is std::forward<Uj>(uj) and its type Vi is Uj&&;

  • (10.4)

    otherwise, the value is tid and its type Vi is TiD cv &.