C++ error: Unable to convert function parameter type, how to modify it?

When programming in C, we often encounter various errors. One of the most common errors is the inability to convert function parameter types. This problem seems relatively simple, but it often causes headaches. Next, we will introduce how to solve this problem.

First, let’s look at a sample code:

#include <iostream>
using namespace std;

void printNum(int num) {
    cout << "The number is: " << num << endl;
}

int main() {
    double num = 3.14;
    printNum(num);
    return 0;
}

The code defines a printNum function to output an integer. In the main function, we define a double-precision floating point number num and then pass it as a parameter to the printNum function. There seems to be no problem with the logic of this code, but the following error message will be prompted:

error: cannot convert 'double' to 'int' for argument '1' to 'void printNum(int)'
     printNum(num);
             ^~~

The error message states: Type double cannot be converted to type int, and Function printNum accepts a parameter of type int. This is because when we call function printNum, the parameter type passed to it is inconsistent with the parameter type in the function declaration.

To solve this problem, the easiest way is to modify the parameter type of the calling function to ensure that the parameter type passed to the function is consistent with the parameter type in the function declaration:

#include <iostream>
using namespace std;

void printNum(int num) {
    cout << "The number is: " << num << endl;
}

int main() {
    double num = 3.14;
    int intNum = static_cast<int>(num);
    printNum(intNum);
    return 0;
}

In the above code , we added a static_cast<int></int> forced type conversion to convert the double-precision floating point number num into an integer intNum, and then intNum is passed to the function printNum as a parameter, thereby avoiding errors of inconsistent parameter types.

Of course, there are other ways to solve this problem, such as changing the parameter type to double when declaring the function, or changing the function parameter type to a template type, etc. But no matter which method is used, we need to always pay attention to the matching of variable and function parameter types in C programming to avoid various errors due to type mismatch.

In short, to solve the problem of being unable to convert function parameter types, you need to pay attention to the setting of the parameter type in the function declaration, and whether the type of the parameter passed when calling the function meets the requirements of the function parameter type. As long as we keep these in mind, we can avoid the trouble caused by this error and successfully write high-quality C programs.

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