Swift - Literals

A literal is the source code representation of a value of an integer, floating-point number, or string type. The following are examples of literals −

42                // Integer literal
3.14159           // Floating-point literal
"Hello, world!"   // String literal

Integer Literals

An integer literal can be a decimal, binary, octal, or hexadecimal constant. Binary literals begin with 0b, octal literals begin with 0o, and hexadecimal literals begin with 0x and nothing for decimal.

Here are some examples of integer literals −

let decimalInteger = 17         // 17 in decimal notation
let binaryInteger = 0b10001     // 17 in binary notation
let octalInteger = 0o21         // 17 in octal notation
let hexadecimalInteger = 0x11   // 17 in hexadecimal notation

Floating-point Literals

A floating-point literal has an integer part, a decimal point, a fractional part, and an exponent part. You can represent floating point literals either in decimal form or hexadecimal form.

Decimal floating-point literals consist of a sequence of decimal digits followed by either a decimal fraction, a decimal exponent, or both.

Hexadecimal floating-point literals consist of a 0x prefix, followed by an optional hexadecimal fraction, followed by a hexadecimal exponent.

Here are some examples of floating-point literals −

let decimalDouble = 12.1875
let exponentDouble = 1.21875e1
let hexadecimalDouble = 0xC.3p0

String Literals

A string literal is a sequence of characters surrounded by double quotes, with the following form −


String literals cannot contain an unescaped double quote ("), an unescaped backslash (\), a carriage return, or a line feed. Special characters can be included in string literals using the following escape sequences −

Escape sequence Meaning
\0 Null Character
\\ \character
\b Backspace
\f Form feed
\n Newline
\r Carriage return
\t Horizontal tab
\v Vertical tab
\' Single Quote
\" Double Quote
\000 Octal number of one to three digits
\xhh... Hexadecimal number of one or more digits

The following example shows how to use a few string literals −

let stringL = "Hello\tWorld\n\nHello\'Swift 4\'"

When we run the above program using playground, we get the following result −

Hello World

Hello'Swift 4'

Boolean Literals

There are three Boolean literals and they are part of standard Swift 4 keywords −

  • A value of true representing true.

  • A value of false representing false.

  • A value of nil representing no value.