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
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
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
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 −
|\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\'" print(stringL)
When we run the above program using playground, we get the following result −
Hello World Hello'Swift 4'
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.