pointer-to-unary-function-class.md

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Learn more about: pointer_to_unary_function Class	pointer_to_unary_function Class	02/21/2019	functional/std::pointer_to_unary	pointer_to_unary_function function pointer_to_unary_function class	05600207-b916-4759-beca-6b6facd2d6f6

pointer_to_unary_function Class

Converts a unary function pointer into an adaptable unary function. Deprecated in C++11, removed in C++17.

Syntax

template <class Arg, class Result>
class pointer_to_unary_function
    : public unary_function<Arg, Result>
{
    explicit pointer_to_unary_function(Result(*pfunc)(Arg));
    Result operator()(Arg left) const;
};

Parameters

pfunc
The binary function to be converted.

left
The object that the *pfunc is called on.

Return Value

The class template stores a copy of pfunc. It defines its member function operator() as returning (* pfunc)(_ Left).

Remarks

A unary function pointer is a function object and may be passed to any C++ Standard Library algorithm that is expecting a unary function as a parameter, but it is not adaptable. To use it with an adaptor, such as binding a value to it or using it with a negator, it must be supplied with the nested types argument_type and result_type that make such an adaptation possible. The conversion by pointer_to_unary_function allows the function adaptors to work with binary function pointers.

Example

The constructor of pointer_to_unary_function is rarely used directly. See the helper function ptr_fun for an example of how to declare and use the pointer_to_unary_function adaptor predicate.