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 −
"characters"
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 −
import Cocoa let stringL = "Hello\tWorld\n\nHello\'Swift\'" println(stringL)
When we run the above program using playground, we get the following result −
Hello World Hello'Swift'
Boolean Literals
There are three Boolean literals and they are part of standard Swift keywords −
- A value of true representing true.
- A value of false representing false.
- A value of nil representing no value.
