Function Parameters and Return Types in C++
In the C++ programming language, function variable parameter values and return data types are important concepts or elements of any user-defined function definition. Functions help C++ users manage how to pass or transfer declared function parameter data type values as actual and formal arguments in a user-defined function, and how to exit a function when needed. Functions in C++ programming help you create modular program source code or functional programs by explaining how and when to define parameters in a custom function and how to define return data types in the proper order.
So, let’s take a closer look at the function parameter and return data type concepts in the C++ programming.
Function Parameter Concept in C++.
Parameters in a function program are user-defined variables that are created within brackets in a custom user-created function definition. These user-defined custom variable parameters serve as placeholders or storage locations for actual data type values that pass value or information when an existing function is called in the program.
Types of C++ Function Parameters.
A basic C++ function program defines several types of function parameter variables.
- Pass-by-value – In a pass-by-value function, a copy of the argument value is provided or passed to the user-defined function parameter.
- Pass-by-reference – The pass-by-reference method provides a user-defined function with an actual reference to an originally declared function argument, allowing the C++ user to modify or replace an argument directly within the function program.
- Pass-by-constant reference – This function method performs similarly to pass-by-reference, but the value passed to this type of function cannot be replaced.
Pass-by-value concept in C++.
The pass-by-value method provides a copy of the argument value passed to the function defined and declared as a parameter. Any modifications to the parameter inside the pass-by-value function have no major impact on the original argument outside the current function.
Pass-by-value syntax in C++.
return_type function_name(parameter1, parameter2, …) {
// Here you can define the function body as per your needs
}
Example of a pass-by-value function.
#include <iostream>
using namespace std;
void grow(int p) {
p++; // here it modifies the local copy of the p parameter
cout << “here it grows inside the function – ” << p << endl;
}
int main() {
int q = 1;
grow(q); // Here it passes a copy of the q parameter value
cout << “here it is stable Inside the main function – ” << q << endl; // Here the q parameter value remains unchanged with the increment operator
return 0;
}
Explanation of the Pass-by-value function method.
- In the pass-by-value example, the function grow accepts the value of the q parameter by value. Even if the p parameter is incremented inside the function with the grow increment operator, the original variable q in the main() function remains unchanged.
Pass-by-reference concept in C++.
In the pass-by-reference function method, a reference value address location (i.e., an alias, both formal and actual) is provided for the argument value passed to the function. Such that any modifications to the function parameter affect the original function argument value.
Syntax of pass-by-reference in C++.
return_type function_name(type ¶meter1, type ¶meter2, …) {
// Here you can define the function body as per your needs
}
Example of pass-by-reference.
#include <iostream>
using namespace std;
void grow(int &p) {
p++; // here it Directly modifies the original parameter variable passed
cout << “here it grows Inside the function – ” << p << endl;
}
int main() {
int q = 1;
grow(q); // here it passes a reference to q parameter
cout << “here it stable Inside the main function – ” << q << endl; //here q parameter is modified
return 0;
}
Explanation of pass-by-reference function method.
- In this pass-by-reference example, the q parameter variable is passed by reference to the incrementing function. Any modifications to the p parameter within the function directly affect the original variable q.
Pass-by-constant reference concept in C++.
In the pass-by-constant reference method, a reference to the argument value is provided to a user-defined function. As such, the original function cannot modify the argument value. The pass-by-constant reference method is used when C++ users want to avoid creating multiple copies of a large function object, but still want to ensure that the current function cannot modify the parameter argument value.
Pass-by-constant reference syntax.
return_type function_name(const type ¶meter1, const type ¶meter2, …) {
// Here you can define the function body as per your needs
}
Example of pass-by-constant reference.
#include <iostream>
using namespace std;
void preview(const int &p) {
cout << “here is the value of the p parameter – ” << p << endl;
/ p++; // it displays an error – cannot modify a const reference variable value
}
int main() {
int q = 7;
preview(q); // here it passes the q parameter by constant reference
return 0;
}
Explanation of pass-by-constant reference function method.
- In the pass-by-constant reference example, the q parameter is passed by constant reference. The function can access the q parameter’s property without copying it, as it cannot modify the original value of the q parameter. This is because the function reference is defined as a const data type.
Function return type concept in C++.
The return data type of a user-defined function indicates the return data type of the parameter value that will return a function value when the function is called in the current program. The return data type can be any valid C++ data type, such as int, float, double, char, or void if the function does not return any value.
Return data type void (no return value) concept in C++.
Remember, a function whose return data type is defined as void cannot return any value to the current program. A void function declaration is used when C++ users want their created function to perform only one action, such as printing some parameter values or modifying a variable by reference to the function parameter, but it does not need to return any data to the function caller.
Syntax of return data type void (no return value).
void function_name() {
// Here you can define the function body as per your needs
}
Example of return data type void (no return).
#include <iostream>
using namespace std;
void message() {
cout << “Welcome to, Vcanhelpsu” << endl;
}
int main() {
message(); // here it calls the function with a void return type method
return 0;
}
Explanation of return data type with void function method.
- Here in the return data type void example, a user-defined function message is declared with a void return type, which means it does not return any value to the current program. It simply prints a user-defined message to the console screen.
