Summary  
The `else` statement enables conditional branching by executing one block of code when an `if` condition is false, ensuring that only one of two alternative paths runs.  

General domain of usage  
Printing different messages based on evaluated conditions.

The `else` statement is a crucial element in controlling the program flow. It complements the `if` statement by allowing a program to take different actions depending on whether a given condition is `true` or `false`. Essentially, it enables the program to **choose between two alternative paths**.

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If the condition is `false`, the code inside the first block (the one following `if`) **is skipped**, and the code inside the second block (the one following `else`) **is executed**.

When executed, it appears to be functioning as expected. Since the variable `x` **is less** than 10, the output correctly states: ```X is not greater than 10```.

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But try to modify the value of a variable `x` to a number greater than 10, and then execute the provided code snippet once more. As you can see there are two distinct messages: one indicating that ```X is greater than 10```, and the other specifying that ```X is not greater than 10```. 

The key thing to understand is that the second `std::cout` statement **is not** part of the `if` block, it is **always be executed unconditionally** after the `if` block resulting in both messages being printed. Of course this has to be fixed and this issue can be resolved by using an `else` keyword.

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Now everything works as expected and **only one of two** instructions will be executed depending on the value of the `x`.

The `else` keyword can be followed by any statement, including another `if` block, and this chain can be extended as necessary, but it's important not to overuse this construct because it can make it challenging to comprehend the program's flow.

Note

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

// Function declaration
double calculateShippingCost(double weightKg);

TEST_CASE("Light package (<= 2 kg) should cost $5", "[calculateShippingCost]") {
double result = calculateShippingCost(1.5);
REQUIRE(result == Approx(5.0));
}

TEST_CASE("Edge case: exactly 2 kg should cost $5", "[calculateShippingCost]") {
double result = calculateShippingCost(2.0);
REQUIRE(result == Approx(5.0));
}

TEST_CASE("Medium package (>2 kg and <=5 kg) should cost $10", "[calculateShippingCost]") {
double result = calculateShippingCost(3.5);
REQUIRE(result == Approx(10.0));
}

TEST_CASE("Edge case: exactly 5 kg should cost $10", "[calculateShippingCost]") {
double result = calculateShippingCost(5.0);
REQUIRE(result == Approx(10.0));
}

TEST_CASE("Heavy package (>=5 kg) should cost $20", "[calculateShippingCost]") {
double result = calculateShippingCost(7.2);
REQUIRE(result == Approx(20.0));
}

test.cpp

Welcome to a beginner-friendly course that will help you learn the core concepts of conditional statements . Whether you're new to programming or looking to improve your understanding of conditional statements and how they influence the flow of your programs, this course is designed to meet your needs.

This is your gateway to understanding the fundamental building blocks of decision making. Gain the essential knowledge to make your programs more intelligent and responsive.

Challenge: Else Statement

解答