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| Categories: functors, adaptors | | Component type: type |
Description
Binder1st is a functors adaptor: it is used to transform an AdaptableBinaryFunction into an AdaptableUnaryFunction. Specifically, if f is an object of class binder1st<AdaptableBinaryFunction>, then f(x) returns F(c, x), where F is an object of class AdaptableBinaryFunction and where c is a constant. Both F and c are passed as arguments to binder1st's constructor. [1]
The easiest way to create a binder1st is not to call the constructor explicitly, but instead to use the helper function bind1st.
Example
Finds the first nonzero element in a list.
List<int> L;
...
List<int>::iterator first_nonzero =
find_if(L.begin(), L.end(), bind1st(not_equal_to<int>(), 0));
assert(first_nonzero == L.end() || *first_nonzero != 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 first 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::second_argument_type,
AdaptableBinaryFunction::result_type>
Members
| Member | Where defined | Description |
argument_type | AdaptableUnaryFunction | The type of the function object's argument, which is AdaptableBinaryFunction::second_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(c, x), where F and c are the arguments with which this binder1st was constructed. |
binder1st(const AdaptableBinaryFunction& F,
AdaptableBinaryFunction::first_argument_type c)
| binder1st | See below |
template <class AdaptableBinaryFunction, class T>
binder1st<AdaptableBinaryFunction>
bind1st(const AdaptableBinaryFunction& F, const T& c);
| binder1st | See below |
New members
These members are not defined in the AdaptableUnaryFunction requirements, but are specific to binder1st.
| Member | Description |
binder1st(const AdaptableBinaryFunction& F,
AdaptableBinaryFunction::first_argument_type c)
| The constructor. Creates a binder1st such that calling it with the argument x (where x is of type AdaptableBinaryFunction::second_argument_type) corresponds to the call F(c, x). |
template <class AdaptableBinaryFunction, class T>
binder1st<AdaptableBinaryFunction>
bind1st(const AdaptableBinaryFunction& F, const T& c);
| If F is an object of type AdaptableBinaryFunction, then bind1st(F, c) is equivalent to binder1st<AdaptableBinaryFunction>(F, c), but is more convenient. The type T must be convertible to AdaptableBinaryFunction::first_argument_type. This is a global function, not a member function. |
Notes
[1] Intuitively, you can think of this operation as "binding" the first 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, binder2nd, AdaptableUnaryFunction, AdaptableBinaryFunction
