Summary  
This chapter explains how to define simple functions with parameters and return values, and how to invoke them to organize and reuse code.

General domain of usage  
Mathematical calculations

#define CATCH_CONFIG_MAIN
#include <catch2/catch.hpp>

double calculateTripCost(double distanceKm);

TEST_CASE("Trip cost for 0 km should be $5.0", "[calculateTripCost]") {
    double result = calculateTripCost(0.0);
    REQUIRE(result == Approx(5.0)); // Base fare 5.0 + 0 * 2.0 = 5.0
}

TEST_CASE("Trip cost for 10 km should be $25.0", "[calculateTripCost]") {
    double result = calculateTripCost(10.0);
    REQUIRE(result == Approx(25.0)); // Base fare 5.0 + 10 * 2.0 = 25.0
}

TEST_CASE("Trip cost for 12.5 km should be $30.0", "[calculateTripCost]") {
    double result = calculateTripCost(12.5);
    REQUIRE(result == Approx(30.0)); // Base fare 5.0 + 12.5 * 2.0 = 30.0
}

TEST_CASE("Trip cost for 0.5 km should be $6.0", "[calculateTripCost]") {
    double result = calculateTripCost(0.5);
    REQUIRE(result == Approx(6.0)); // Base fare 5.0 + 0.5 * 2.0 = 6.0
}

TEST_CASE("Trip cost for 100 km should be $205.0", "[calculateTripCost]") {
    double result = calculateTripCost(100.0);
    REQUIRE(result == Approx(205.0)); // Base fare 5.0 + 100 * 2.0 = 205.0
}

TEST_CASE("Trip cost for fractional km 7.75 should be $20.5", "[calculateTripCost]") {
    double result = calculateTripCost(7.75);
    REQUIRE(result == Approx(20.5)); // Base fare 5.0 + 7.75 * 2.0 = 20.5
}

test.cpp

Explore the world of C++ functions and delve into their fundamental concepts and practical applications. Gain proficiency in declaring, using, and optimizing functions, including parameter handling, scope management, and function overloading. Learn about recursion, templates, and lambda expression for robust C++ programming. Develop the skills to create modular, efficient, and reusable functions for real-world coding challenges.

Now it's time to dive into the world of C++ functions! Now you will learn some general concepts about functions in C++, including their definition, declaration, and usage. Discover how to declare and call functions, and gain insights into variable scopes, both local and global, for effective program design.

We will delve into specifying and using function arguments in C++ programming. Explore concepts like pass-by-value and pass-by-reference, and understand the role of default arguments; learn how to pass arrays as function arguments and become familiar with constant function arguments.

Now we will learn about how to specify the return value of a function in C++. This includes understanding the data types that functions can return, such as integers, floating-point numbers, and arrays. We will also consider function that have no return value.

Now let's delve into some additional topic in C++! We will explore function overloading, mastering the art of creating multiple functions with the same name but different parameter lists for enhanced code flexibility. Recursion is introduced, teaching the principles of recursive functions, allowing students to solve complex problems efficiently. Additionally, the section covers lambda functions, providing insights into creating concise anonymous functions/

Challenge: Simple Function Creation

Example

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Challenge: Simple Function Creation

Example

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