Macro with arguments - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a macro named SQUARE that calculates the square of a number.

C

#define SQUARE([1]) (([1]) * ([1]))

int main() {
    int x = 5;
    int result = SQUARE(x);
    return 0;
}

Drag options to blanks, or click blank then click option'

Anum

Bx

Cval

Dn

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to put parentheses around the argument in the macro definition.

Using invalid characters or spaces in the macro argument.

The macro argument name can be any valid identifier. Here, n is used as the argument name for clarity.

2fill in blank

medium

Complete the macro definition to create a macro MAX that returns the maximum of two values a and b.

C

#define MAX(a, b) (([1]) > (b) ? (a) : (b))

int main() {
    int max_val = MAX(3, 7);
    return 0;
}

Drag options to blanks, or click blank then click option'

AMAX

Ba

Cb

Dc

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping the arguments in the comparison, which changes the logic.

Forgetting parentheses around macro arguments.

The macro compares a and b. The first operand in the comparison should be a.

3fill in blank

hard

Fix the error in the macro to correctly compute the cube of a number x.

C

#define CUBE(x) (([1]) * (x) * (x))

int main() {
    int c = CUBE(3);
    return 0;
}

Drag options to blanks, or click blank then click option'

Ax

BCUBE

C3

Dy

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different variable name than the macro argument.

Hardcoding a number instead of using the argument.

The macro argument x must be used consistently to compute the cube.

4fill in blank

hard

Fill both blanks to define a macro MIN that returns the minimum of two values x and y.

C

#define MIN([1], [2]) ((([1]) < ([2])) ? ([1]) : ([2]))

int main() {
    int m = MIN(10, 20);
    return 0;
}

Drag options to blanks, or click blank then click option'

Ax

By

Ca

Db

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing argument names or using different names in different parts.

Forgetting parentheses around arguments.

The macro arguments are x and y. Use them consistently in the macro.

5fill in blank

hard

Fill all three blanks to define a macro SWAP that swaps two variables a and b using a temporary variable temp.

C

#define SWAP([1], [2], [3]) \
    do { \
        int [3] = [1]; \
        [1] = [2]; \
        [2] = [3]; \
    } while(0)

int main() {
    int x = 5, y = 10;
    SWAP(x, y, temp);
    return 0;
}

Drag options to blanks, or click blank then click option'

Aa

Bb

Ctemp

Dswap

Attempts:

3 left

💡 Hint

Common Mistakes

Using the same name for the temporary variable and one of the variables to swap.

Forgetting the do-while(0) structure for safe macro usage.

The macro swaps variables a and b using a temporary variable temp.

Practice

1. What does a macro with arguments in C do?

easy

A. It replaces code snippets with given values before compilation

B. It creates a new function at runtime

C. It allocates memory dynamically

D. It executes code conditionally during runtime

Solution

1. Step 1: Understand macro replacement

   Macros with arguments are replaced by the preprocessor before the program runs, substituting the macro call with the code snippet using the given arguments.

2. Step 2: Differentiate from functions

   Unlike functions, macros do not create executable code at runtime but perform textual substitution during compilation.

3. Final Answer:

   It replaces code snippets with given values before compilation -> Option A

4. Quick Check:

   Macro = code substitution before compile [OK]

Hint: Macros replace code before running, not at runtime [OK]

Common Mistakes:

• Thinking macros create functions
• Confusing macros with runtime code
• Assuming macros allocate memory

2. Which of the following is the correct syntax for defining a macro with two arguments a and b that adds them?

easy

A. #define ADD(a, b) a + b

B. #define ADD a, b (a + b)

C. #define ADD(a, b) (a + b)

D. #define ADD(a, b) {a + b}

Solution

1. Step 1: Check macro argument syntax

   Macro arguments must be enclosed in parentheses immediately after the macro name, like ADD(a, b).

2. Step 2: Ensure proper expression grouping

   To avoid operator precedence issues, the expression should be enclosed in parentheses: (a + b).

3. Final Answer:

   #define ADD(a, b) (a + b) -> Option C

4. Quick Check:

   Correct macro syntax = #define NAME(args) (expression) [OK]

Hint: Always put parentheses around macro arguments and whole expression [OK]

Common Mistakes:

• Missing parentheses around arguments
• Not enclosing expression in parentheses
• Using braces {} instead of parentheses

3. Given the macro definition #define SQUARE(x) x * x, what is the output of printf("%d", SQUARE(3 + 1));?

medium

A. Error

B. 16

C. 12

D. 7

Solution

1. Step 1: Expand the macro with argument

   The macro call SQUARE(3 + 1) expands to 3 + 1 * 3 + 1 because the macro definition lacks parentheses around the expression.

2. Step 2: Apply operator precedence

   Multiplication has higher precedence, so 3 + (1 * 3) + 1 = 3 + 3 + 1 = 7.

3. Final Answer:

   7 -> Option D

4. Quick Check:

   Without parentheses, macro expands incorrectly = 7 [OK]

Hint: Without parentheses, macro args can cause wrong math [OK]

Common Mistakes:

• Assuming macro adds parentheses automatically
• Ignoring operator precedence
• Expecting 16 as square of 4

4. Identify the error in this macro definition: #define MULTIPLY(a, b) a * b)

medium

A. Extra closing parenthesis at the end

B. Missing opening parenthesis before a

C. Arguments should not have parentheses

D. Macro name should be lowercase

Solution

1. Step 1: Check parentheses balance

   The macro ends with an extra closing parenthesis ")" that does not match any opening parenthesis.

2. Step 2: Confirm correct macro syntax

   Macro should be defined as #define MULTIPLY(a, b) (a * b) with balanced parentheses around the expression.

3. Final Answer:

   Extra closing parenthesis at the end -> Option A

4. Quick Check:

   Parentheses must be balanced in macro definitions [OK]

Hint: Count parentheses carefully in macro definitions [OK]

Common Mistakes:

• Ignoring unmatched parentheses
• Thinking arguments can't have parentheses
• Believing macro names must be lowercase

5. You want to create a macro MAX(a, b) that returns the larger of two values. Which definition correctly handles expressions as arguments without errors?

hard

A. #define MAX(a, b) ((a > b) ? a : b)

B. #define MAX(a, b) ((a) > (b) ? (a) : (b))

C. #define MAX(a, b) a > b ? a : b

D. #define MAX(a, b) (a > b ? a : b)

Solution

1. Step 1: Understand argument safety

   To safely handle expressions as arguments, each argument must be enclosed in parentheses to avoid precedence errors.

2. Step 2: Check full macro expression grouping

   The entire conditional expression should be enclosed in parentheses to ensure correct evaluation when used in larger expressions.

3. Final Answer:

   #define MAX(a, b) ((a) > (b) ? (a) : (b)) -> Option B

4. Quick Check:

   Parentheses around args and whole expression prevent bugs [OK]

Hint: Always parenthesize macro args and whole expression [OK]

Common Mistakes:

• Missing parentheses around arguments
• Not enclosing entire expression
• Assuming macro works like a function