Literals

• These are values hard coded as such in the code.

print(18)        // 18 is an Integer literal
print(3.14)      // 3.14 is a Double literal
print("Hello")   // "Hello" is a String literal
print(true)      // true is a Boolean literal

• Type of the literal is automatically inferred.
• Numeric literals of difference bases

18          // Decimal integer literal
2.5e3       // Decimal double literal. This evaluates to 2.5 x 103
0b1010      // Binary literal has a prefix of 0b
0o1357      // Octal literal has a prefix of 0o
0x15AF      // Hex literal has a prefix of 0x
0xABCDEFp5  // Hex literal with exponent. This evaluates to 0xABCDEF x 25

Constants

• The syntax for declaring constants is

let constantName: TypeName = value/object

• Examples

let message: String = "Hello"  // message is an immutable String
let pi = 3.14                  // Automatic Type Inference to Double
let a: Int                     // Despite being a constant (immutable), the value is
                               // not assigned here. This is possible, provided you
                               // set the value during initialization, which is
                               // discussed later.
let a, b, c: Int               // All 3 constants are of type Int
let a: Int, b, c: String       // "a" is Int, "b" and "c" are Strings
let a = 1, b = 2, c = 3.14     // "a" and "b" are Ints, "c" is a Double

Variables

• The syntax for declaring variables is

var variableName: TypeName = value/object

• Examples

var message: String = "Hello"  // message is a mutable String
var pi = 3.14                  // Automatic type inference to Double 
var a: Int

var a, b, c: Int
var a: Int, b, c: String
var a = 1, b = 2, c = 3.14

Naming Constants & Variables

• Almost any character (including Unicode) can be used for names.
• Can not use math symbols, box drawing characters, arrows etc.
• Can not begin with numbers.

Commenting Code

• Single line comment using    //

print("Hello World!")  // This is a comment

• Multi line comment using    /*   */

/*
    print("Hello")
    print("World")
*/

• Comments can be nested    /*   /*  */   */

/*
    print("Hello")  
    /*
        print("World")  // Some comment
    */
*/

Semicolon

• Semicolon at the end of statement is is not mandatory (unless next statement is on the same line).