Int, Double, Float number types in Swift - Mini Project: Build & Apply

Working with Int, Double, and Float Number Types in Swift

📖 Scenario: You are creating a simple Swift program to understand how to use different number types: Int, Double, and Float. These types help you store whole numbers and decimal numbers with different precision.

🎯 Goal: Build a Swift program that declares variables of type Int, Double, and Float, assigns values to them, and prints their values to see how they work.

📋 What You'll Learn

Declare an Int variable named wholeNumber with the value 42.

Declare a Double variable named decimalNumber with the value 3.14159.

Declare a Float variable named smallDecimal with the value 2.718.

Print all three variables with descriptive text.

💡 Why This Matters

🌍 Real World

Understanding number types is essential for any app that works with calculations, measurements, or data input.

💼 Career

Many programming jobs require knowledge of how to handle different numeric data types correctly to avoid errors and ensure precision.

1

Declare an Int variable

Create a variable called wholeNumber of type Int and set it to 42.

Swift

# Your code here

Hint

Use var to declare a variable and specify the type Int with a colon.

2

Declare Double and Float variables

Add a variable called decimalNumber of type Double with the value 3.14159, and a variable called smallDecimal of type Float with the value 2.718.

Swift

var wholeNumber: Int = 42
# Your code here

Hint

Remember to specify the type after the variable name with a colon, and assign the correct decimal values.

3

Print the variables

Use three print statements to display the values of wholeNumber, decimalNumber, and smallDecimal with descriptive text. For example, print "Whole number: 42" for wholeNumber.

Swift

var wholeNumber: Int = 42
var decimalNumber: Double = 3.14159
var smallDecimal: Float = 2.718
# Your code here

Hint

Use string interpolation with \(variableName) inside the print statements.

4

Run and see the output

Run the program to display the values of wholeNumber, decimalNumber, and smallDecimal.

Swift

var wholeNumber: Int = 42
var decimalNumber: Double = 3.14159
var smallDecimal: Float = 2.718
print("Whole number: \(wholeNumber)")
print("Decimal number: \(decimalNumber)")
print("Small decimal: \(smallDecimal)")
# Run the program

Hint

Check the console output matches the expected text exactly.

Practice

1.

Which Swift type is best to store the number 42 without any decimal part?

easy

A. String

B. Double

C. Float

D. Int

Solution

1. Step 1: Understand the number type

   The number 42 is a whole number without decimals.

2. Step 2: Match with Swift types

   Int stores whole numbers, while Double and Float store decimal numbers.

3. Final Answer:

   Int -> Option D

4. Quick Check:

   Whole number = Int [OK]

Hint: Whole numbers use Int, decimals use Double or Float [OK]

Common Mistakes:

• Choosing Double or Float for whole numbers
• Confusing String with number types

2.

Which of the following is the correct way to declare a variable price as a Double with value 19.99 in Swift?

?

easy

A. var price: Int = 19.99

B. var price = 19.99f

C. var price: Double = 19.99

D. var price: Float = "19.99"

Solution

1. Step 1: Check type and value compatibility

   Double can store decimal numbers like 19.99 correctly.

2. Step 2: Validate syntax

   var price: Double = 19.99 uses correct syntax: variable name, type annotation, and decimal value.

3. Final Answer:

   var price: Double = 19.99 -> Option C

4. Quick Check:

   Double declaration syntax = var name: Double = value [OK]

Hint: Use var name: Double = value for decimals [OK]

Common Mistakes:

• Using 'f' suffix which is invalid in Swift
• Assigning decimal to Int type
• Using quotes for numbers

3.

What will be the output of this Swift code?

let a: Float = 3.14
let b: Double = 3.14
print(a == b)

medium

A. false

B. true

C. Compile-time error

D. Runtime error

Solution

1. Step 1: Understand type comparison

   Float and Double are different types; comparing them directly requires conversion.

2. Step 2: Check equality operation

   Swift allows comparing Float and Double, but values may differ due to precision, so a == b is false.

3. Final Answer:

   false -> Option A

4. Quick Check:

   Float vs Double equality = false [OK]

Hint: Float and Double differ in precision; direct equality often false [OK]

Common Mistakes:

• Assuming Float and Double are equal if values look same
• Expecting compile error for comparing different types

4.

Identify the error in this Swift code snippet:

var x: Int = 10.5
var y: Float = 20

medium

A. Cannot assign integer 20 to Float variable

B. Cannot assign decimal 10.5 to Int variable

C. Missing semicolon after variable declarations

D. Variable names are invalid

Solution

1. Step 1: Check variable type and assigned value

   Variable x is Int but assigned 10.5 which is a decimal number.

2. Step 2: Validate other assignments

   Variable y is Float and assigned 20 (an integer), which is allowed by implicit conversion.

3. Final Answer:

   Cannot assign decimal 10.5 to Int variable -> Option B

4. Quick Check:

   Int cannot hold decimals [OK]

Hint: Int variables cannot hold decimal values [OK]

Common Mistakes:

• Thinking Float cannot hold integer values
• Expecting semicolons in Swift
• Assuming variable names are invalid

5.

You want to store the value 0.123456789 in Swift with the highest precision possible. Which type should you choose and why?

hard

A. Double, because it stores decimal numbers with more precision

B. Float, because it uses less memory

C. Int, because it stores whole numbers accurately

D. String, to keep exact digits

Solution

1. Step 1: Understand precision needs

   The number 0.123456789 has many decimal places requiring high precision.

2. Step 2: Compare Swift types for precision

   Double stores decimal numbers with more precision than Float; Int stores whole numbers only.

3. Step 3: Consider String

   String stores text, not numbers, so it cannot be used for numeric calculations.

4. Final Answer:

   Double, because it stores decimal numbers with more precision -> Option A

5. Quick Check:

   Highest decimal precision = Double [OK]

Hint: Use Double for precise decimal numbers [OK]

Common Mistakes:

• Choosing Float for high precision decimals
• Using Int for decimal numbers
• Using String for numeric calculations