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Number types and literals

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Example

Swift's built-in numeric types are:

Literals

A numeric literal's type is inferred from context:

let x = 42    // x is Int by default
let y = 42.0  // y is Double by default

let z: UInt = 42     // z is UInt
let w: Float = -1    // w is Float
let q = 100 as Int8  // q is Int8

Underscores (_) may be used to separate digits in numeric literals. Leading zeros are ignored.

Floating point literals may be specified using significand and exponent parts («significand» e «exponent» for decimal; 0x «significand» p «exponent» for hexadecimal).

Integer literal syntax

let decimal = 10               // ten
let decimal = -1000            // negative one thousand
let decimal = -1_000           // equivalent to -1000
let decimal = 42_42_42         // equivalent to 424242
let decimal = 0755             // equivalent to 755, NOT 493 as in some other languages
let decimal = 0123456789

let hexadecimal = 0x10         // equivalent to 16
let hexadecimal = 0x7FFFFFFF
let hexadecimal = 0xBadFace
let hexadecimal = 0x0123_4567_89ab_cdef

let octal = 0o10               // equivalent to 8
let octal = 0o755              // equivalent to 493
let octal = -0o0123_4567             

let binary = -0b101010         // equivalent to -42
let binary = 0b111_101_101     // equivalent to 0o755
let binary = 0b1011_1010_1101  // equivalent to 0xB_A_D

Floating-point literal syntax

let decimal = 0.0
let decimal = -42.0123456789
let decimal = 1_000.234_567_89

let decimal = 4.567e5               // equivalent to 4.567×10⁵, or 456_700.0
let decimal = -2E-4                 // equivalent to -2×10⁻⁴, or -0.0002
let decimal = 1e+0                  // equivalent to 1×10⁰, or 1.0

let hexadecimal = 0x1p0             // equivalent to 1×2⁰, or 1.0
let hexadecimal = 0x1p-2            // equivalent to 1×2⁻², or 0.25
let hexadecimal = 0xFEEDp+3         // equivalent to 65261×2³, or 522088.0
let hexadecimal = 0x1234.5P4        // equivalent to 0x12345, or 74565.0
let hexadecimal = 0x123.45P8        // equivalent to 0x12345, or 74565.0
let hexadecimal = 0x12.345P12       // equivalent to 0x12345, or 74565.0
let hexadecimal = 0x1.2345P16       // equivalent to 0x12345, or 74565.0
let hexadecimal = 0x0.12345P20      // equivalent to 0x12345, or 74565.0