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Standard Template Library Programmer's Guide
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binder1st<AdaptableBinaryFunction>



Categories: functors, adaptors	Component type: type

Description

Binder1st 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 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

Adaptable Unary Function

Type requirements

AdaptableBinaryFunction must be a model of Adaptable Binary Function.

Public base classes

unary_function<AdaptableBinaryFunction::second_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::second_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(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 Adaptable Unary Function 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.