How to convert function pointer to function object and vice versa?

In C, function pointers can be converted into function objects through the std::function template: Use std::function to wrap function pointers into function objects. Use the std::function::target member function to convert a function object to a function pointer. This transformation is useful in scenarios such as event handling, function callbacks, and generic algorithms, providing greater flexibility and code reusability.

How to convert function pointer to function object and vice versa

In C, function pointer and function object are two closely related concepts that allow us Work with functions in a more flexible way. In some cases, you may want to convert a function pointer to a function object, or vice versa.

Convert function pointer to function object

You can convert function pointer to function object by using std::function template. std::function Accepts any callable entity (including function pointers) and wraps it in a callable object.

// 函数指针
int add(int a, int b) { return a + b; }

// 转换为函数对象
std::function<int(int, int)> add_fn = add;

// 调用函数对象
int result = add_fn(10, 20);  // 结果为 30

Convert function object to function pointer

To convert function object to function pointer, you can use the std::function::target member function. This function returns a function pointer to the underlying function of the function object.

std::function<int(int, int)> add_fn = [](int a, int b) { return a + b; };

// 转换为函数指针
int (*add_ptr)(int, int) = add_fn.target<int (*)(int, int)>();

// 调用函数指针
int result = add_ptr(10, 20);  // 结果为 30

Practical case

In the following scenarios, you may find it useful to convert a function pointer to a function object or vice versa:

• Event Handling: Function objects are useful when you need to call the same function in different contexts.
• Function callbacks: Function pointers are useful when you need to pass a function as a parameter to another function.
• Generic Algorithms: std::function Can be used to pass any callable entity to a generic algorithm, providing flexibility.

By understanding the conversion between function pointers and function objects, you can write more flexible and reusable code.

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