Question

Rewrite the following expressions using an if...else statement. (Assume that all variables are declared properly.) a. \(\quad(x<5) ? \quad y=10: y=20\) b. \((\text { fuel }>=10)\) ? drive \(=150:\) drive \(=30\) c. (booksBought \(>=3\) ) ? discount \(=0.15\) : discount \(=0.0\)

Short answer

Convert each ternary operator to if-else: a) If x < 5, set y = 10, else y = 20; b) If fuel >= 10, drive = 150, else drive = 30; c) If booksBought >= 3, discount = 0.15, else 0.0.

Step-by-step solution

Understanding Expressions

The given expressions are ternary operators, which are a concise way to write shortened if-else statements. They are of the form: `condition ? expression_if_true : expression_if_false`. Your task is to convert these into standard if-else syntax.

Statement a - Conversion

For the expression \((x<5) ? y=10: y=20\), rewrite it using if-else notation:```cppif (x < 5) { y = 10;} else { y = 20;}```Here, if \(x < 5\) is true, then \(y\) is set to 10. Otherwise, \(y\) is set to 20.

Statement b - Conversion

For the expression \((\text{fuel}>=10) ? \text{drive}=150: \text{drive}=30\), rewrite it using if-else:```cppif (fuel >= 10) { drive = 150;} else { drive = 30;}```Here, if \(\text{fuel} \geq 10\) is true, then \(\text{drive}\) is set to 150. Otherwise, it is set to 30.

Statement c - Conversion

For the expression \((\text{booksBought} >= 3) ? \text{discount} = 0.15 : \text{discount} = 0.0\), rewrite it using if-else:```cppif (booksBought >= 3) { discount = 0.15;} else { discount = 0.0;}```Here, if \(\text{booksBought} \geq 3\) is true, then \(\text{discount}\) is set to 0.15. Otherwise, it is set to 0.0.

Key concepts

Understanding if-else Statements

In C++ programming, if-else statements are fundamental building blocks for creating decision-making logic. An if-else statement allows your program to perform certain actions based on whether a specified condition evaluates as true or false. Here's how it works: when the condition in the if statement is true, the code block associated with the if statement is executed. If the condition is false, the code block following the else statement is executed.

Consider it as a basic fork in the road for your program's flow of execution. You have the logical condition acting as a gatekeeper deciding which path (code block) gets to execute. For example, in the expression `if (x < 5) { y = 10; } else { y = 20; }`, if `x` is less than 5, the variable `y` is set to 10. If `x` is not less than 5, `y` is set to 20 instead.

• The condition uses comparison or logical operators to evaluate a true or false value.
• If the condition is true, the if block executes.
• If the condition is false, the else block executes.

It's important to ensure that conditions are meaningful and help steer your program effectively.

Ternary Operators: A Concise Alternative

Ternary operators in C++ offer a shorthand way to write simple if-else statements. They are particularly useful when you need to assign a value to a variable based on a condition. The syntax of a ternary operator is: `condition ? expression_if_true : expression_if_false;`

This single line allows you to do in one quick statement what it would typically take several lines to accomplish with an if-else block. For example, the ternary expression `(x < 5) ? y = 10 : y = 20;` quickly allows `y` to take the value of 10 if `x` is less than 5, otherwise, `y` takes the value of 20.

• It's compact and can make the code look cleaner.
• Best used for simplicity and when making quick assignments.
• Preferably should not replace complex if-else logic due to potential readability issues.

Having ternary operators in your programmer's toolbox is handy, but be cautious of overusing them. Their brevity can be helpful, but sometimes it's worth using a classic if-else for clarity and maintainability reasons.

Exploring Conditional Expressions

Conditional expressions are the criteria evaluated to determine the flow of control in if-else statements or the result of ternary operators. In C++, these conditions are usually combinations of relational and logical operations. These operations compare values and variables and decide whether to execute specific blocks of code.

For example, in the statement `if (booksBought >= 3)`, `booksBought >= 3` is a conditional expression. It checks if the number of books bought is greater than or equal to 3. If true, certain actions, like setting a discount, can be triggered. Think of conditional expressions as questions that your code needs answers to, to move in the right direction.

• Common operators include `==`, `!=`, `>`, `<`, `>=`, and `<=`.
• Logical operators like `&&` (AND), `||` (OR), and `!` (NOT) often combine multiple conditions.
• Make sure conditions are precise to avoid unexpected behavior in your program's logic.

Understanding how to structure these expressions correctly is essential for implementing effective flow control in your programs.