Function pointers and closures compared to other languages

In computer science, function pointers can store function addresses, while closures can access variables in the scope when they were created. Function pointers and closures are widely supported in dynamically typed languages ​​such as JavaScript and Python, and support is also provided in statically typed languages ​​such as C and Java. Closures and function pointers are implemented differently in different languages, for example C supports function pointers and closures, Java supports closures but not function pointers, and Python and JavaScript support both function pointers and closures.

Function pointers and closures: comparison with other languages

In computer science, function pointers and closures are two different things A powerful programming tool that allows programmers to use functions as first-class citizens. They are particularly common in dynamically typed languages ​​such as JavaScript and Python, but are also widely supported in statically typed languages ​​such as C and Java.

Function pointer

A function pointer is a function address reference stored in memory. Using function pointers, programmers can easily pass functions to other functions or objects.

Closure

A closure is a function that has access to variables in the scope when it was created. This makes closures particularly useful in scenarios where you need to retain access to the state of the environment when the function was created.

Comparison with other languages

Function pointers and closures are implemented in different ways in different programming languages. Here is a comparison of some common languages:

Language	Function Pointer	Closure
C	Supported	Supported
Java	Not supported	Support
Python	Support	Support
JavaScript	Support	Support

Practical case

Consider the following scenario: We have a function that takes as input each item in the list elements plus 2. We can use a function pointer to pass this function and use a closure to retain access to the additive offset.

C

#include <functional>
#include <vector>

using namespace std;

int add_two(int x) { return x + 2; }

int main() {
  vector<int> numbers = {1, 2, 3, 4, 5};
  function<int(int)> add_func = add_two;

  for_each(numbers.begin(), numbers.end(), [&add_func](int& x) { x = add_func(x); });

  // 打印修改后的数字
  for (int num : numbers) {
    cout << num << " ";
  }
  cout << endl;

  return 0;
}

Python

def add_two(x):
  return x + 2

numbers = [1, 2, 3, 4, 5]
add_func = lambda x: add_two(x)

map(add_func, numbers)  # 修改 numbers 中的每个元素

# 打印修改后的数字
print(numbers)

In these examples we use function pointers add_func Pass the add_two function to the for_each and map functions. Closures allow us to use add_func variables inside these functions to achieve the desired behavior.

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