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| Categories: functors, adaptors | Component type: type |
Description
Pointer_to_binary_function is a functors adaptor that allows a function pointer Result (*f)(Arg1, Arg2) to be treated as an AdaptableBinaryFunction. That is: if F is a pointer_to_binary_function<Arg1, Arg2, Result> that was initialized with an underlying function pointer f of type Result (*)(Arg1, Arg2), then F(x, y) calls the function f(x, y). The difference between f and F is that pointer_to_binary_function is an AdaptableBinaryFunction, i.e. it defines the nested typedefs first_argument_type, second_argument_type, and result_type.
Note that a function pointer of type Result (*)(Arg1, Arg2) is a perfectly good BinaryFunction object, and may be passed to an STL algorithm that expects an argument that is a BinaryFunction. The only reason for using the pointer_to_binary_function class is if you need to use an ordinary function in a context that requires an AdaptableBinaryFunction, e.g. as the argument of a function object adaptor.
Most of the time, you need not declare an object of type pointer_to_binary_function directly. It is almost always easier to construct one using the ptr_fun function.
Example
The following code fragment finds the first string in a list that is equal to "OK". It uses the standard library function strcmp as an argument to a function object adaptor, so it must first use a pointer_to_binary_function adaptor to give strcmp the AdaptableBinaryFunction interface.
List<char*> L;
...
List<char*>::iterator item =
find_if(L.begin(), L.end(),
not1(binder2nd(ptr_fun(strcmp), "OK")));
Definition
Defined in the standard header functional, and in the nonstandard backward-compatibility header function.h.
Template parameters
| Parameter | Description | Default |
Arg1 | The function object's first argument type | |
Arg2 | The function object's second argument type | |
Result | The function object's result type | |
Model of
AdaptableBinaryFunction
Type requirements
Public base classes
binary_function<Arg1, Arg2, Result>
Members
| Member | Where defined | Description |
first_argument_type | AdaptableBinaryFunction | The type of the first argument: Arg1. |
second_argument_type | AdaptableBinaryFunction | The type of the second argument: Arg2 |
result_type | AdaptableBinaryFunction | The type of the result: Result |
Result operator()(Arg1 x, Arg2 y) | BinaryFunction | Function call operator. |
pointer_to_binary_function(Result (*f)(Arg1, Arg2)) | pointer_to_binary_function | See below. |
pointer_to_binary_function() | pointer_to_binary_function | See below. |
template <class Arg1, class Arg2, class Result>
pointer_to_unary_function<Arg1, Arg2, Result>
ptr_fun(Result (*x)(Arg1, Arg2));
| pointer_to_binary_function | See below. |
New members
These members are not defined in the AdaptableBinaryFunction requirements, but are specific to pointer_to_binary_function.
| Member | Description |
pointer_to_binary_function(Result (*f)(Arg1, Arg2)) | The constructor. Creates a pointer_to_binary_function whose underlying function is f. |
pointer_to_binary_function() | The default constructor. This creates a pointer_to_binary_function that does not have an underlying function, and that therefore cannot actually be called. |
template <class Arg1, class Arg2, class Result>
pointer_to_unary_function<Arg1, Arg2, Result>
ptr_fun(Result (*x)(Arg1, Arg2));
| If f is of type Result (*)(Arg1, Arg2) then ptr_fun(f) is equivalent to pointer_to_binary_function<Arg1,Arg2,Result>(f), but more convenient. This is a global function, not a member function. |
Notes
See also
pointer_to_unary_function, ptr_fun, AdaptableBinaryFunction
