Question

State whether the following are valid switch statements. If not, explain why. Assume that \(n\) and digit are int variables. a. switch \((n<=2)\) \\{ case 0: cout \(<<\) "Draw." \(<<\) endl break; case 1: cout \(<<\) "Win. " \(<<\) endl break; case 2: cout \(<<\) "Lose." \(<<\) endl break; \\} b. switch (digit / 4 ) \\{ case 0 case 1: cout \(<<\) "Iow. " \(<<\) endl break; case 1 case 2: cout \(<<\) "middle." \(<<\) endl break; case 3: cout \(<<\) "high." \(<<\) endl c. switch \((n \quad \text { \& } \quad 6)\) \\{ case 1: case 2: case 3: case 4: case 5: cout \(<

Short answer

Statements a, b, and d are invalid due to syntax errors. Only statement c is technically valid, but incomplete due to syntax issues.

Step-by-step solution

Check Syntax of Switch Statements

Review the syntax of a switch statement in C++. A switch statement requires an expression in parentheses, a series of cases with constant expressions, an optional default case, and colons (:) after each case.

Analyze Switch Statement a

The expression `(n<=2)` is not valid for switch statements as switch requires an integral or enumeration type, but a boolean expression returns true (1) or false (0). Additionally, there is a missing semicolon in `endl break`.

Analyze Switch Statement b

This switch uses `(digit / 4)` as its expression, which is valid as long as `digit` is an `int`. However, only one `case` can be followed by a block of code without a `break;`. Missing colons and semicolons make the cases invalid.

Analyze Switch Statement c

The expression \(n \ \&\ 6\) is valid with bitwise operation resulting in integral type. This case would work if the expression evaluates to an expected case value. However, there's a syntax error since `<<n` is not valid due to missing context (like ending using `<<` operator) and missing break statements leave cases open.

Analyze Switch Statement d

The expression `(n 8 10)` is syntactically invalid as it is missing an operator between 'n', '8', and '10'. Therefore, it cannot be used as a switch expression. The case statements also lack colons, and `cout` lacks stream insertion operators '<<' and needed semicolons.

Key concepts

C++ syntax

Understanding C++ syntax is key to programming correctly and avoiding common errors. In C++, a switch statement is a control structure that works by evaluating an expression and executing different code blocks based on the value of the expression.
To write a C++ switch statement correctly:

• Start with the keyword switch followed by an expression in parentheses.
• Enclose the block of code with cases in curly braces {}.
• Begin each case with the keyword case followed by a constant expression or value, ending with a colon :.
• Optionally include a default case to handle unexpected values.
• Use break; to exit the switch after a case executes, preventing fall-through.

Following correct syntax helps the compiler understand and execute your code as intended. Missing components or incorrect usage leads to syntax errors.

switch case structure

The switch case structure in C++ is a way to simplify multi-path decision-making in programs. It is typically used when there are several conditions for executing different parts of the code, making it preferable over using multiple if-else statements.
Here’s a breakdown of the switch case structure:

• Switch Expression: This expression determines which case to execute. It could be a variable or any expression that evaluates to an integer type.
• Case Labels: Each case label follows the keyword case and is concluded with a colon :. It contains code that executes when the case value matches the switch expression evaluation.
• Break Statement: Placing a break; at the end of a case block is crucial. It tells the program to jump out of the switch structure after the execution of that particular case.
• Default Case: This section executes if no case values match the expression. It's the catch-all part and is optional, but recommended for handling unexpected values.

Properly structured switch case statements make programs cleaner and more efficient.

valid switch expressions

Switch statements in C++ depend on valid switch expressions. The expression evaluated in a switch must return an integer, character, or enumeration type. This is different from a boolean expression, which only returns true (1) or false (0) and is not suitable for switch statements.
Here are some examples of valid switch expressions:

• Integral Values: Expressions that evaluate to an integer, such as simple arithmetic operations or constants, are valid.
• Enumeration Constants: If you use enum constants in your switch expressions, they are valid as they map to integer values.
• Char data type: Since char values are internally stored as integers (ASCII values), they are also valid.

Incorrect or complex expressions will lead to compile-time errors. Make sure the expression aligns with these standards to ensure your program runs smoothly.

switch statement errors

Switch statements are powerful, but they can also result in errors if not used correctly. Errors typically stem from syntactical mistakes or inappropriate expressions. Below are some common errors and tips to avoid them:

• Missing Breaks: Omission of a break; statement leads to fall-through, executing subsequent cases even if they do not match the expression, unless this behavior is intentional.
• Incorrect Expression Types: Ensure the switch expression is an integer, character, or enumeration type, not a boolean or complex datatype.
• Missing Colons: Each case label should end with a colon :, not a semicolon ;. Forgetting this causes errors or unintended behavior.
• Unmatched Parentheses: When using parentheses in expressions, ensure each opening parenthesis has a corresponding closing parenthesis.
• Inadequate Stream Operations: Ensure that all I/O operations, like cout, have complete stream insertion (<<) and terminate properly with semicolons ;.

Carefully checking and correcting these common mistakes can prevent faulty code execution and save debugging time.