How do C++ function pointers compare and contrast with lambda expressions?

Function pointers and Lambda expressions are both techniques for encapsulating code blocks in C, and they are different. A function pointer is a constant pointer to the memory address of a function, while a lambda expression is an anonymous function with a more flexible syntax that captures external variables. Function pointers are suitable for scenarios where type safety and low overhead are required, and lambda expressions are suitable for scenarios where anonymity and capturing external variables are required.

C Function Pointers and Lambda Expressions: Compare and Contrast

Introduction

In C, functions Pointers and lambda expressions are both techniques for encapsulating blocks of code, but differ in their syntax and usage.

Function pointer

The function pointer is a constant pointer pointing to the memory address of the function. It allows functions to be passed as arguments or stored in data structures.

Lambda expression

Lambda expression is an anonymous function defined using a special syntax. They are often used to create small blocks of code that can be passed as callbacks or filters.

Compare

Feature	Function pointer	Lambda expression
Syntax	int (*func)(int)	[](int x) { return x * x; }
Anonymity	Non-Anonymity	Anonymity
Capture	Cannot capture external variables	Can capture external variables
Type safety	Type safety	Type safety is weak

Practical case

Function pointer as parameter:

void sort(int arr[], int size, int (*comp)(int, int)) {
  // 使用函数指针作为比较函数进行排序
  ...
}

int compareAsc(int a, int b) {
  return a - b;
}

int main() {
  int arr[] = {5, 2, 8, 3, 1};
  sort(arr, 5, compareAsc);
  ...
}

Lambda expression as callback:

std::vector<int> numbers = {1, 2, 3, 4, 5};
auto even = [](int x) { return x % 2 == 0; };
std::vector<int> evenNumbers = std::remove_if(numbers.begin(), numbers.end(), even);
...

Conclusion

Function pointers and lambda expressions are used in C to encapsulate code blocks Useful tool. Function pointers are suitable for scenarios where type safety and low overhead are required, while lambda expressions are better suited for scenarios where anonymity and capturing external variables are required.

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