Use Cases of Default Parameters and Parameters Check

In programming, there are different ways to handle function parameters, such as checking the validity of the passed arguments or setting default values for parameters. Here are some differences between parameter checking and default values:

1. Parameter checking ensures that the arguments passed to a function are valid and within the expected range, whereas default values are used when a parameter is not explicitly set by the caller.

2. Parameter checking can help prevent unexpected errors and bugs caused by invalid input values, whereas default values can make function calls more concise and convenient by allowing the caller to omit certain parameters.

3. Parameter checking can provide more flexibility and control over how a function behaves, whereas default values can simplify the function signature and make it easier to use.

4. Parameter checking can be more computationally expensive, especially if the input validation is complex, whereas default values are usually simple and have minimal performance impact.

5. Parameter checking is often used when the caller cannot guarantee the validity of the input, whereas default values are commonly used when the caller can make assumptions about the input or when a certain value is more common.
   

#include <stdio.h>

// Function that accepts two parameters with default values
void printMessage(char* message, int times) {
    // Set default value for times parameter
    if (times <= 0) {
        times = 1;
    }

    // Print message the specified number of times
    for (int i = 0; i < times; i++) {
        printf("%s\n", message);
    }
}

// Main function
int main() {
    // Call printMessage with valid arguments
    printMessage("Hello world!", 3);

    // Call printMessage with invalid times parameter
    printMessage("Invalid times", -1);

    return 0;
}

In the printMessage function, we have two parameters: message, which is a pointer to a string, and times, which is an integer that specifies how many times the message should be printed. We have set a default value for times by checking if it's less than or equal to 0, and if so, we set it to 1.

In the main function, we call printMessage twice: once with valid arguments, and once with an invalid times parameter. The first call will print "Hello world!" three times, and the second call will print "Invalid times" once (since the default value of 1 is used).

This example demonstrates the use of default values to simplify function calls and the use of parameter checking to handle invalid input values.

In general, both parameter checking and default values are useful techniques in programming, and their use depends on the specific needs and requirements of the function and its callers. A good practice is to use both techniques when appropriate, for example, by providing sensible default values for common input scenarios and performing parameter checking for critical input values.