What are the application scenarios of function pointers in C++ functional programming?

Function pointers are mainly used in C functional programming: higher-order functions: functions that receive or return functions. Anonymous function: A function created through a lambda expression. Callback function: A function called when other functions are executed.

Application scenarios of function pointers in C functional programming

A function pointer is a pointer to a function. In C functional programming, it is widely used in the following scenarios:

1. Higher-order functions:

Higher-order functions receive functions as parameters or return functions. Function pointers can be used to implement higher-order functions such as map, filter, and reduce.

2. Anonymous function:

Anonymous function is a function defined outside the call point. We can create an anonymous function using a lambda expression and assign it to a function pointer.

3. Callback function:

The callback function is a function called when other functions are executed. They are often used for asynchronous programming or event handling. Function pointers provide a way to manage callback functions.

Practical case:

Consider the following code that needs to filter the list:

std::vector<int> numbers = {1, 2, 3, 4, 5};

bool isEven(int n) {
  return n % 2 == 0;
}

std::vector<int> evenNumbers;
for (int number : numbers) {
  if (isEven(number)) {
    evenNumbers.push_back(number);
  }
}

We can use function pointersauto isEven = [ ](int n) { return n % 2 == 0; } To rewrite this code:

std::vector<int> evenNumbers = std::remove_if(numbers.begin(), numbers.end(), isEven);

Functionstd::remove_if Using a function pointer as a parameter will satisfy Elements given a condition are removed from the list. In this case we use it to remove odd numbers.

Other applications:

Other applications of function pointers in C functional programming include:

• Creating customizable strategy patterns
• Define function objects with variable behavior
• Implement function object factories

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