Integers

Integers are whole numbers, like 1, 2, or -7, with no fractions or decimal points.

In this page:

Declaring Integers
Integer Arithmetic
Sized Integer Types

Declaring Integers

The Int type represents whole numbers and is the default choice for integer values in Swift, automatically inferred from whole-number literals.

Example: Declaring Integers

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let apples = 5
let oranges = 3
print("Total fruit: \(apples + oranges)")

Integer Arithmetic

Swift supports the standard arithmetic operators on integers: addition, subtraction, multiplication, integer division, and the remainder operator.

Note: Integer division truncates any fractional part -- 17 / 5 is 3, not 3.4.

Example: Integer Arithmetic

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let a = 17
let b = 5
print("\(a) / \(b) = \(a / b), remainder \(a % b)")

Sized Integer Types

Beyond Int, Swift offers explicitly sized types like Int8, Int16, Int32, and Int64 for when you need to control exactly how much memory a value uses, such as when interfacing with specific binary formats.

Note: Underscores in numeric literals like 9_000_000_000 are ignored by the compiler and just help readability.

Example: Sized Integer Types

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let small: Int8 = 100
let big: Int64 = 9_000_000_000
print("Int8: \(small), Int64: \(big)")

Common Mistakes

Assuming Int is always 32-bit; on modern platforms Int is 64-bit, matching the native word size.
Overflowing a fixed-size integer type like Int8 and being surprised by a runtime crash instead of silent wraparound.
Mixing Int and UInt (or Int and Double) in an expression directly instead of explicitly converting first.

Chapter Summary

Int is the default integer type and matches the platform's native word size (64-bit on modern systems).
Swift also has sized variants like Int8, Int16, Int32, Int64, and unsigned versions like UInt.
Arithmetic operators (+, -, *, /, %) work as expected on integers.
Integer overflow is checked and traps at runtime rather than silently wrapping, unless you use overflow-safe operators like &+.

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Integers

Declaring Integers

Integer Arithmetic

Sized Integer Types

Chapter Quiz — Complete all 8 topics to unlock

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