Swift Lexical Structure
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Last Updated on March 13, 2022 by Deya Eldeen

Swift lexical structure, consists of valid tokens (lowest-level building blocks) that form the structure of any swift program, these tokens describe the rest of whole swift language…

A token consists of an identifier, keyword, punctuation, literal, or operator.

1) Identifiers:
An example of an identifier is a variable name, for example here “pet” is an identifier.

let pet = "Happy Dinosaur πŸ¦–";

Identifiers support unicode characters, you can name you variable in you native language, and as in other programming languages, you cannot use keywords as identifiers, this is still possible if you surrounding a keyword with back-ticks,

var `var` = "var"

examples of unicode identifiers are

var _latitude = 32.0;
var をップル = "apple"

2) Keywords:
The list of basic keywords in swift are listed below, see (Swift Reserved Keywords) for comprehensive list and details.


3) Literals:
literals fall into 3 categories, integer, floating point, and string literals

Integer Literals
var a = 10

var b = 00010100b

var c = 14x

var d = 24o

leading zeros will be ignored by the compiler, and the use of underscores is possible to increase readability.

var a = 100_000_000

Floating Point Literals
//Simple floating point number
var a = 10.7

//Exponent floating point number
var b = 10.6e2

var c = 10.1e-2
//Exponent floating point number

//Hexa decimal exponent
var d = 0xAp2

//Hexa decimal exponent
var d = 0xAp-2

String Literals

String literals are characters are enclosed within double quotes. Strings can contain escape sequences to represent characters like qoutes. Example for string literal is shown below.

var a = “test”
var a = “Hello\nWorld”

\0 Null Character
\ Backslash
\t Horizontal Tab
\n New line
\r Carriage Return
\” Double Quote
\’ Single Quote

4) Operators:
There are different operators supported in swift which includes
+ : Addition
– : Subtraction
* : Multiplication
/ : Division
% : Remainder
^ : Exponent
& : Bitwise And
&& : Logical And
| : Bitwise Or
|| : Logical Or
++ : Increment Operator
– : Minus
~ : Bitwise Not
< : Less Than
> : Greater Than
… etc.

Keep in mind, as in Swift’s official documentation, this is a list of reserved punctuation and can’t be used as custom operators:
(){}[].,:;=@#& (as a prefix operator), ->`?, and ! (as a postfix operator)”

Swift Whitespace:
White spaces are used to separate tokens and to distinguish prefixes, otherwise it’s normally omitted by the compiler.

Swift Comments:
these are statements that are ignored by the compiler, and meant for documentation purposes of our code, they could be either one-line or multi-line.

// This is a single line comment

/* Multi line (block) comment - can have
more than one line! */

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