<functional> (TR1)

Defines several templates that help construct function objects, which are objects of a type that defines operator(). A function object can be a function pointer, but more typically, the object is used to store additional information that can be accessed during a function call.

#include <functional>

Remarks

The following features are added by using TR1:

• A call signature is the name of a return type followed by a parenthesized comma-separated list of zero or more argument types.

• A call wrapper is an object of a call wrapper type.

• A call wrapper type is a type that holds a callable object and supports a call operation that forwards to that object.

• A callable object is an object of a callable type.

• A callable type is a pointer to function, a pointer to member function, a pointer to member data, or a class type whose objects can appear immediately to the left of a function call operator.

• A target object is the callable object held by a call wrapper object.

The pseudo-function INVOKE(f, t1, t2, ..., tN) means one of the following things:

• (t1.*f)(t2, ..., tN) when f is a pointer to member function of class T and t1 is an object of type T or a reference to an object of type T or a reference to an object of a type derived from T.

• ((*t1).*f)(t2, ..., tN) when f is a pointer to member function of class T and t1 is not one of the types described in the previous item.

• t1.*f when f is a pointer to member data of class T and t1 is an object of type T or a reference to an object of type T or a reference to an object of a type derived from T.

• (*t1).*f when f is a pointer to member data of class class T and t1 is not one of the types described in the previous item.

• f(t1, t2, ..., tN) in all other cases.

The pseudo-function INVOKE(f, t1, t2, ..., tN, R) means INVOKE(f, t1, t2, ..., tN) implicitly converted to R.

If a call wrapper has a weak result type, the type of its member type result_type is based on the type T of the target object of the wrapper, as follows:

• If T is a pointer to function, result_type is a synonym for the return type of T.

• If T is a pointer to member function, result_type is a synonym for the return type of T.

• If T is a pointer to data member, result_type is a synonym for the declared type of the data member.

• If T is a class type that has a member type result_type, then result_type is a synonym for T::result_type.

• Otherwise, there is no member result_type.

Every call wrapper has a copy constructor. A simple call wrapper is a call wrapper that has an assignment operator and whose copy constructor and assignment operator do not throw exceptions. A forwarding call wrapper is a call wrapper that can be called by using an argument list t1, t2, ..., tN, where each ti is an lvalue.

The call wrappers defined in this header support function call operators that have arguments of types T1, T2, ..., TN, where 0 <= N <= NMAX. In this implementation, the value of NMAX is 10.

Declarations

Class	Description
bad_function_call Class	Reports a bad function call.
function Class	Wrapper for a callable object.
hash Class	Computes a hash code for a value.
is_bind_expression Class	Tests whether type is generated by calling bind.
is_placeholder Class	Tests whether type is a placeholder.
reference_wrapper Class	Wraps a reference.
result_of Class	The return type of a wrapped callable object.

Object	Description
_1 Object	Placeholders for replaceable arguments.

Template Functions

Operator	Description
operator== <function>	Disallows equality comparison of callable objects.
operator!= <function>	Disallows inequality comparison of callable objects.

Function	Description
bind Function	Binds arguments to a callable object.
cref Function	Constructs a const reference_wrapper from an argument.
mem_fn Function	Generates a simple call wrapper.
ref Function	Constructs a reference_wrapper from an argument.
swap Function <functional>	Swaps two function objects.

See Also

Other Resources

Standard C++ Library TR1 Extensions Reference