How to solve C++ syntax error: 'expected identifier before '(' token'?

How to solve C syntax error: 'expected identifier before '(' token'?

In the process of C programming, we often encounter various Syntax error. One of the common errors is: 'expected identifier before '(' token'. This error usually occurs when calling a function. The compiler cannot recognize the function name or some necessary identifiers are missing from the function parameter list. This article We will introduce how to solve this syntax error and give some code examples.

First, we need to clarify what causes this error. In C, a function call requires a function name and parameter list, And enclosed in parentheses. When the function name does not exist or the necessary identifier is missing from the parameter list, the compiler will report an error, prompting 'expected identifier before '(' token'.

In order to better solve this Error, we can follow the following steps:

1. Check the function name: First, we need to check whether the function name is correct. Confirm the correct spelling, case and namespace of the function name. If the function If the function name is a custom function, then we need to ensure that it has been declared and defined correctly. If the function name is a function provided by the standard library or a third-party library, we need to import the correct library file.

Here is an example that shows an error caused by misspelling the function name in a function call:

// 错误示例
int res = summ(3, 5); // 函数名应为sum而非summ

// 正确示例
int res = sum(3, 5); // 函数名正确为sum

2. Check the parameter list: Next, we need to check the parameter list in the function call. Confirm the number of parameters , type and order are consistent with the function declaration or definition. If the function requires that the parameter passed in is an object of a certain class, we need to ensure that the class has been correctly defined and declared. If the parameter is a literal or constant, we need to confirm Whether the format and type of the parameter value are correct.

The following is an example showing an error caused by missing identifiers in the parameter list when a function is called:

// 错误示例
int res = sum(3, ); // 缺少第二个参数标识符

// 正确示例
int res = sum(3, 5); // 参数列表中包含了正确的两个整数参数

3. Check the header File: Sometimes, we need to import the corresponding header file before using the function. The header file contains the declaration or definition of the function. If the header file is not imported correctly, the compiler will not be able to recognize the function name. Therefore, we need to ensure that it is correct The required header files are introduced.

The following is an example showing the error caused by not introducing the correct header files when calling a function:

// 错误示例
#include <iostream>

int main() {
  cin >> num; // 缺少引入<iostream>头文件

  return 0;
}

// 正确示例
#include <iostream>

int main() {
  int num;
  std::cin >> num; // 引入<iostream>头文件，并使用std::cin进行输入

  return 0;
}

To summarize, when we encounter When encountering C syntax error: 'expected identifier before '(' token', we should check whether the function name, parameter list, and header file are correct. Through careful inspection and troubleshooting, we can solve this type of syntax error. I hope the solutions and sample code provided in this article can be helpful to you and help you better perform C programming.

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