Numeric literal formats in Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a hexadecimal integer literal.

Swift

let hexNumber = 0[1]1A

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

Ab

Bo

Cx

Dd

Attempts:

3 left

💡 Hint

Common Mistakes

Using 0b or 0o instead of 0x for hexadecimal.

Forgetting the letter after 0.

In Swift, hexadecimal literals start with 0x.

2fill in blank

medium

Complete the code to declare a binary integer literal.

Swift

let binaryNumber = 0[1]1011

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

Ax

Bo

Cd

Db

Attempts:

3 left

💡 Hint

Common Mistakes

Using 0x or 0o instead of 0b for binary.

Omitting the prefix.

Binary literals in Swift start with 0b.

3fill in blank

hard

Fix the error in the code to declare an octal integer literal.

Swift

let octalNumber = 0[1]17

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

Ao

Bx

Cb

Dd

Attempts:

3 left

💡 Hint

Common Mistakes

Using 0b or 0x instead of 0o for octal.

Writing octal numbers without prefix.

Octal literals in Swift start with 0o.

4fill in blank

hard

Fill both blanks to declare a floating-point literal with an exponent.

Swift

let floatNumber = 1.25[1]3[2]2

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

Ae

Bp

C+

D-

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'p' instead of 'e' for decimal exponents.

Omitting the sign after the exponent.

Floating-point literals with decimal exponents use e followed by a plus or minus sign.

5fill in blank

hard

Fill all three blanks to declare a hexadecimal floating-point literal with a negative exponent.

Swift

let hexFloat = 0x1.[1]p[2][3]

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

A8

B4

C-

D+

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'e' instead of 'p' for hexadecimal floating-point literals.

Omitting the sign before the exponent.

Hexadecimal floating-point literals use p followed by a sign and exponent number.

Practice

1. Which of the following is a valid binary numeric literal in Swift?

easy

A. 0b1010

B. 0x1010

C. 1010b

D. 0o1010

Solution

1. Step 1: Understand binary literal format in Swift

   Binary literals start with 0b followed by 0s and 1s.

2. Step 2: Check each option

   0b1010 uses 0b prefix correctly. 0x1010 is hexadecimal, C is invalid, A is octal.

3. Final Answer:

   0b1010 -> Option A

4. Quick Check:

   Binary literals start with 0b = D [OK]

Hint: Binary literals always start with 0b prefix [OK]

Common Mistakes:

• Confusing binary (0b) with hexadecimal (0x)
• Placing the b suffix after the number
• Using octal prefix 0o for binary

2. Which of the following is the correct way to write the number one million using underscores in Swift?

easy

A. 1_00_0000

B. 1000_000

C. 10_00_000

D. 1_000_000

Solution

1. Step 1: Understand underscore usage in numeric literals

   Underscores can be placed anywhere between digits to improve readability.

2. Step 2: Check each option for correct grouping

   1_000_000 groups digits in thousands correctly. Others have irregular grouping which is allowed but uncommon and confusing.

3. Final Answer:

   1_000_000 -> Option D

4. Quick Check:

   Use underscores to separate thousands = A [OK]

Hint: Use underscores every three digits for clarity [OK]

Common Mistakes:

• Placing underscores at the start or end of number
• Using inconsistent grouping that confuses readers
• Thinking underscores change the value

3. What is the output of the following Swift code?

let number = 1.5e2
print(number)

medium

A. 150.0

B. 1.5e2

C. 15.0

D. SyntaxError

Solution

1. Step 1: Understand scientific notation in Swift

   1.5e2 means 1.5 x 10², which equals 150.0.

2. Step 2: Evaluate the print output

   Printing the number shows the decimal value 150.0, not the literal string.

3. Final Answer:

   150.0 -> Option A

4. Quick Check:

   1.5e2 = 150.0 [OK]

Hint: e2 means multiply by 10 squared [OK]

Common Mistakes:

• Thinking print shows the literal string '1.5e2'
• Confusing e2 with e-2 (which divides)
• Assuming integer output instead of floating-point

4. Identify the error in this Swift numeric literal:

let value = 0b1021

medium

A. Should use 0x prefix for binary

B. Binary literals cannot contain digits other than 0 or 1

C. Missing underscore for readability

D. Floating-point literals cannot use binary format

Solution

1. Step 1: Check digits allowed in binary literals

   Binary literals only allow digits 0 and 1 after the 0b prefix.

2. Step 2: Analyze the given literal

   The literal contains digit 2, which is invalid for binary (only 0s and 1s allowed).

3. Final Answer:

   Binary literals cannot contain digits other than 0 or 1 -> Option B

4. Quick Check:

   Binary digits only 0 or 1 = C [OK]

Hint: Binary digits must be only 0 or 1 [OK]

Common Mistakes:

• Thinking underscores are mandatory
• Confusing binary prefix 0b with hexadecimal 0x
• Assuming floating-point literals can be binary

5. You want to represent the decimal number 255 in Swift using hexadecimal and octal literals. Which pair of literals correctly represents 255?

hard

A. 0xFF and 0o255

B. 0x255 and 0o255

C. 0xFF and 0o377

D. 0x377 and 0oFF

Solution

1. Step 1: Convert decimal 255 to hexadecimal

   255 decimal equals FF in hexadecimal, so 0xFF is correct.

2. Step 2: Convert decimal 255 to octal

   255 decimal equals 377 in octal, so 0o377 is correct.

3. Final Answer:

   0xFF and 0o377 -> Option C

4. Quick Check:

   255 decimal = 0xFF hex & 0o377 oct [OK]

Hint: Hex FF = 255 decimal; Oct 377 = 255 decimal [OK]

Common Mistakes:

• Confusing octal digits with decimal digits
• Using decimal digits after 0x prefix
• Mixing up hexadecimal and octal prefixes