 

Categories: functors, adaptors   Component type: type 
Description
Binder2nd
is a functors adaptor: it is used to transform an AdaptableBinaryFunction into an AdaptableUnaryFunction. 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 backwardcompatibility 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
AdaptableUnaryFunction
Type requirements
AdaptableBinaryFunction
must be a model of AdaptableBinaryFunction.
Public base classes
unary_function<AdaptableBinaryFunction::first_argument_type,
AdaptableBinaryFunction::result_type>
Members
Member  Where defined  Description 
argument_type  AdaptableUnaryFunction  The type of the function object's argument, which is AdaptableBinaryFunction::first_argument_type 
result_type  AdaptableUnaryFunction  The type of the result: AdaptableBinaryFunction::result_type 
result_type operator()(const argument_type& x) const
 AdaptableUnaryFunction  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 AdaptableUnaryFunction 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 functors, binder1st
, AdaptableUnaryFunction, AdaptableBinaryFunction