C++ Function Return Values ​​Guide: A Deep Dive into Types and Meanings

C function return value types include basic types, custom types, pointers, references and void. The meaning of the return value can vary depending on the context and includes operation results, status indications, output parameters, and no return value. Practical cases demonstrate the use of return values ​​in summing and obtaining user names, allowing us to understand the code logic and data flow.

Guide to C Function Return Values: An In-depth Exploration of Types and Meanings

Introduction

The function return value in C is a crucial part of understanding the code logic and data flow. This article will comprehensively explore the types and meanings of C function return values, and deepen understanding through practical cases.

1. Function return value type

C functions can have various return types, including:

• Basic data types : int, double, char, etc.
• User-defined types: Class, structure, union, etc.
• Pointer: Points to a specific memory Pointer to location
• Reference: Reference as an alias to another variable
• void: Type that does not return any value

2. Meaning of function return value

The meaning of function return value depends on the context in which it is used. It can represent:

• The result of the operation: Contains the value calculated during the execution of the function (for example, a sum or average).
• Status indication: Indicates a problem or status (for example, success or failure) encountered during function execution.
• Output parameters: Serve as a mechanism for passing function results to the calling code (e.g., by reference).
• No return value: If the function does not have a meaningful return value, the void type can be used.

3. Practical case

In order to deeply understand the function return value, let’s take a look at a practical case:

int sum(int a, int b) {
  return a + b;
}

string get_username() {
  // 模拟数据库查询
  string username = "John Doe";
  return username;
}

int main() {
  int result = sum(10, 20);  // 储存函数返回值
  cout << "Sum: " << result << endl;
  
  string user = get_username();  // 储存函数返回值
  cout << "Username: " << user << endl;
  
  return 0;
}

at In main function:

• sum The function is called, and its return value (30) is stored in the result variable.
• get_username The function is called and its return value ("John Doe") is stored in the user variable.

Conclusion

Through this article, we have an in-depth discussion of C function return value types and meanings. Understanding function return values ​​is critical to understanding code logic and data flow. Through the provided practical examples, we demonstrate how to use function return values ​​effectively.

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