Книга: Standard Template Library Programmer
binder2nd
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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 |
|---|---|
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. |
Notes
[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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