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binder2nd<AdaptableBinaryFunction>

Categories: functors, adaptors Component type: type

Description

Binder2nd is a function object adaptor: it is used to transform an adaptable binary function into an adaptable unary function. Specifically, if f is an object of class binder2nd<AdaptableBinaryFunction>, then f(x) returns F(x, c), where F is an object of class AdaptableBinaryFunction and where c is a constant. Both F and c are passed as arguments to binder2nd's constructor. [1]

The easiest way to create a binder2nd is not to call the constructor explicitly, but instead to use the helper function bind2nd.

Example

Finds the first positive number in a list.
list<int> L;
...
list<int>::iterator first_positive = 
       find_if(L.begin(), L.end(), bind2nd(greater<int>(), 0));
assert(first_positive == L.end() || *first_positive > 0);

Definition

Defined in the standard header functional, and in the nonstandard backward-compatibility header function.h.

Template parameters

Parameter Description Default
AdaptableBinaryFunction The type of the binary function whose second argument is being bound to a constant.  

Model of

Adaptable Unary Function

Type requirements

AdaptableBinaryFunction must be a model of Adaptable Binary Function.

Public base classes

unary_function<AdaptableBinaryFunction::first_argument_type,
               AdaptableBinaryFunction::result_type>

Members

Member Where defined Description
argument_type Adaptable Unary Function The type of the function object's argument, which is AdaptableBinaryFunction::first_argument_type
result_type Adaptable Unary Function The type of the result: AdaptableBinaryFunction::result_type
result_type operator()(const argument_type& x) const
Adaptable Unary Function Function call. Returns F(x, c), where F and c are the arguments with which this binder1st was constructed.
binder2nd(const AdaptableBinaryFunction& F,
          AdaptableBinaryFunction::second_argument_type c)
binder2nd See below
template <class AdaptableBinaryFunction, class T>
binder2nd<AdaptableBinaryFunction> 
bind2nd(const AdaptableBinaryFunction& F, const T& c);
binder2nd See below

New members

These members are not defined in the Adaptable Unary Function requirements, but are specific to binder2nd.
Member Description
binder2nd(const AdaptableBinaryFunction& F,
          AdaptableBinaryFunction::second_argument_type c)
The constructor. Creates a binder2nd such that calling it with the argument x (where x is of type AdaptableBinaryFunction::first_argument_type) corresponds to the call F(x, c).
template <class AdaptableBinaryFunction, class T>
binder2nd<AdaptableBinaryFunction> 
bind2nd(const AdaptableBinaryFunction& F, const T& c);
If F is an object of type AdaptableBinaryFunction, then bind2nd(F, c) is equivalent to binder2nd<AdaptableBinaryFunction>(F, c), but is more convenient. The type T must be convertible to AdaptableBinaryFunction::second_argument_type. This is a global function, not a member function.

[1] Intuitively, you can think of this operation as "binding" the second argument of a binary function to a constant, thus yielding a unary function. This is a special case of a closure.

See also

The function object overview, binder1st, Adaptable Unary Function, Adaptable Binary Function


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