Swift - Constants, Variables & Print function

In Swift, constants and variables associate a name with a value of a particular type. The value of a constant cannot be changed after it's set, whereas a variable can be set to a different value in the future.

Let's dive into constants, variables, and the print function in Swift:

1. Constants:

Constants are declared using the let keyword. Once set, the value of a constant cannot be changed.

let pi = 3.14159

2. Variables:

Variables are declared using the var keyword.

var age = 25
age = 26  // This is valid because age is a variable

3. Type Annotations:

You can provide a type annotation when you declare a constant or variable, to be clear about the kind of values the constant or variable can store:

var userName: String
userName = "Alice"

4. Multiple Assignments:

You can declare multiple constants or multiple variables on a single line, separated by commas:

let x = 10, y = 20, z = 30
var red, green, blue: Double

5. Print Function:

The print(_:separator:terminator:) function is a global function in Swift that writes one or more values to the standard output.

Basic Usage:
```
print("Hello, World!")
```
Printing Variables and Constants:
```
var greeting = "Hello"
let name = "Alice"
print("\(greeting), \(name)!")
```
This uses string interpolation (\()) to insert constants or variables into a string.
Using separator and terminator:
```
print("Red", "Green", "Blue", separator: " - ", terminator: "!")
```
This will output: Red - Green - Blue!

Conclusion:

Swift offers a straightforward way to define constants and variables using the let and var keywords respectively. The language's static typing, combined with its type inference capabilities, makes it both powerful and user-friendly. The print function, meanwhile, is versatile and provides options to customize the output format, making debugging and logging easier.

How to declare constants in Swift:
- Description: Constants in Swift are declared using the let keyword. Once a value is assigned to a constant, it cannot be changed.
- Code:
```
let pi = 3.14159
print(pi)
```
Defining variables in Swift programming:
- Description: Variables in Swift are declared using the var keyword. Unlike constants, variables can have their values changed after they are initially set.
- Code:
```
var age = 25
age = 26 // Valid, as it's a variable
print(age)
```
Print statements with variables in Swift:
- Description: Print statements in Swift can include variables for displaying their values.
- Code:
```
let name = "John"
var score = 95

print("Player: \(name), Score: \(score)")
```
Concatenating strings in Swift print:
- Description: Strings and variables can be concatenated in print statements in Swift.
- Code:
```
let firstName = "Alice"
let lastName = "Smith"

print("Full Name: " + firstName + " " + lastName)
```
Formatting output with print in Swift:
- Description: The print function in Swift allows formatting output using various options.
- Code:
```
let price = 29.99

// Formatting with precision
print(String(format: "Price: %.2f", price))
```

Swift multiline print statements:

Description: Multiline print statements in Swift can be achieved by using line breaks (\n).

Code:

let message = """
               Hello,
               This is a multiline
               message in Swift.
               """
print(message)

Using constants and variables in Swift examples:
- Description: Constants and variables can be used in various combinations to create dynamic and flexible code.
- Code:
```
let maxAttempts = 3
var currentAttempts = 0

while currentAttempts < maxAttempts {
    print("Attempt \(currentAttempts + 1)")
    currentAttempts += 1
}
```
Swift type annotations for variables:
- Description: Swift allows specifying the type of a variable using type annotations.
- Code:
```
var message: String = "Hello, Swift!"

// Type annotation for an integer
var count: Int = 10
```