Detailed explanation of C++ function parameters: Examples of parameter passing in higher-order functions

There are two parameter passing mechanisms in C: pass by value and pass by address. Pass-by-address passes the memory address of the object to the function, while pass-by-value passes a copy of the value to the function. Higher-order functions are functions that accept functions as parameters, and their parameter passing requires special attention because the passed functions may have different parameter signatures and return types. In the example, the std::sort function is a higher-order function that accepts a comparison function as a parameter and sorts the integers in a std::vector according to the function.

C Detailed explanation of function parameters: Examples of parameter passing in higher-order functions

Introduction

Function parameters are the means of passing data from the calling function to the called function. Understanding the mechanics of parameter passing is crucial to writing robust and readable code. This article will take an in-depth look at parameter passing in C, focusing on examples of parameter passing in higher-order functions.

Pass by value

Pass by value is the simplest and most commonly used parameter passing mechanism. Under this mechanism, a copy of the value is passed to the function, so modifications to the parameters within the function do not affect the original value. This is achieved via a const reference type or value type.

Pass-in-address

Pass-in-address passes the memory address of the actual object to the function. This means that the function can modify the original value. This can be achieved with non-const reference types or pointer types.

Higher-order functions

Higher-order functions are functions that accept functions or function pointers as parameters. Parameter passing in higher-order functions requires special attention, as the passed functions may have different parameter signatures and return types.

Practical case: Sorting function

std::sort is a widely used sorting function in the C standard library. It is a high-order Function that accepts a comparison function as a parameter. Here is an example showing parameter passing for std::sort:

#include <algorithm>
#include <vector>

bool compareInts(int a, int b) {
  return a < b;
}

int main() {
  std::vector<int> nums = {1, 5, 2, 9, 3};
  std::sort(nums.begin(), nums.end(), compareInts);
  for (auto num : nums) {
    std::cout << num << " "; // 输出：1 2 3 5 9
  }
  std::cout << std::endl;
}

In this example, the compareInts function is a higher-order function that takes two Takes an integer as argument and returns a Boolean value. The std::sort function takes the compareInts function as its third parameter, thereby sorting the nums containers based on the comparison result of compareInts Integers are sorted.

Conclusion

Understanding parameter passing in C is crucial to writing robust and maintainable code. Parameter passing in higher-order functions introduces a certain complexity, but through careful attention to the function's signature and underlying mechanism, they can be managed effectively.

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