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Introduction To The Art Of Programming Using Scala Pdf

How to Master the Art of Programming with Scala: A Comprehensive Guide (PDF)

Scala is a modern, JVM-based language that combines the best features of functional and object-oriented programming. It is a powerful and expressive language that can be used for both small and large projects. Scala is also an ideal language for teaching beginning programming, as it introduces many concepts from CS1 and CS2 in a clear and concise way.

introduction to the art of programming using scala pdf

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In this article, we will give you an introduction to the art of programming using Scala. We will cover the following topics:

Scala basics: expressions, types, values, variables, conditionals, functions, and more.

Object-oriented programming: classes, objects, inheritance, polymorphism, abstract classes, traits, and more.

Functional programming: higher-order functions, anonymous functions, closures, collections, map, filter, fold, and more.

Data structures: arrays, lists, sets, maps, tuples, options, and more.

Multithreading and networking: concurrency, futures, promises, actors, sockets, and more.

By the end of this article, you will have a solid foundation for taking on larger-scale projects using Scala. You will also be able to download a PDF version of this article for your reference.

Scala Basics

Scala is a statically typed language, which means that every expression has a type that is checked at compile time. Scala also supports type inference, which means that you don't have to explicitly declare the type of every variable or function. Scala can infer the type from the context or the value assigned to it.

Scala has a rich set of basic types for representing numbers, characters, strings, booleans, and more. Here are some examples of Scala expressions and their types:

// Numbers

1 // Int

1.0 // Double

1 + 2 // Int

1.0 + 2.0 // Double

1 / 2 // Int

1.0 / 2.0 // Double

// Characters

'a' // Char

'A' // Char

'\n' // Char (newline)

'\u0041' // Char (Unicode for A)

// Strings

"Hello" // String

"Hello" + "World" // String

"Hello".length // Int

"Hello".charAt(0) // Char

// Booleans

true // Boolean

false // Boolean

!true // Boolean (negation)

true && false // Boolean (and)

true false // Boolean (or)

// Unit

() // Unit (represents no value)

println("Hello") // Unit (side effect)

You can use the Scala REPL (Read-Eval-Print Loop) to evaluate Scala expressions interactively. The REPL is a command-line tool that lets you enter Scala expressions and see their results immediately. You can start the REPL by typing scala in your terminal. Here is an example session:

$ scala

Welcome to Scala 2.13.6 (OpenJDK 64-Bit Server VM 11.0.11).

Type in expressions for evaluation. Or try :help.

scala> 1 + 2

val res0: Int = 3

scala> "Hello".length

val res1: Int = 5

scala> println("Hello")

Hello

scala> :quit

You can also use Scala scripts to write and run Scala programs in a file. A Scala script is a file with the extension .scala that contains Scala expressions and statements. You can run a Scala script by typing scala filename.scala in your terminal. Here is an example script:

// hello.scala

println("Hello World")

You can run it by typing scala hello.scala in your terminal:

$ scala hello.scala

Hello World

In Scala, you can name values and variables using the val and var keywords respectively. A value is immutable, which means that it cannot be reassigned once it is initialized. A variable is mutable, which means that it can be reassigned to different values during its lifetime.

// Values

val x = 1 // x is a value of type Int with value 1

x = 2 // error: reassignment to val

// Variables

var y = 1 // y is a variable of type Int with value 1

y = 2 // y is now 2

y = y + 1 // y is now 3

In general, it is recommended to use values over variables whenever possible, as they make your code more readable and less prone to errors.

In Scala, you can use conditional expressions to make decisions based on some conditions. The syntax of a conditional expression is if (condition) thenExpression else elseExpression. The condition must be a boolean expression, and the thenExpression and elseExpression must have the same type. The conditional expression evaluates to the thenExpression if the condition is true, or to the elseExpression if the condition is false.

// Conditional expressions

val x = 10

val y = if (x > 0) "Positive" else "Negative" // y is "Positive"

val z = if (x % 2 == 0) x / 2 else x * 2 // z is 5

// Nested conditional expressions

val w = if (x > 0)

if (x % 2 == 0) "Even positive" else "Odd positive"

else

if (x % 2 == 0) "Even negative" else "Odd negative"

// w is "Even positive"

In Scala, you can define and use functions to perform specific tasks or computations. A function has a name, a list of parameters, a return type, and a body. The syntax of a function definition is def name(parameter: Type): ReturnType = body. The parameter list can be empty or contain multiple parameters separated by commas. The return type can be omitted if it can be inferred from the body. The body can be a single expression or a block of statements enclosed by curly braces.

// Function definitions

// A function that takes no parameters and returns Unit (no value)

def greet(): Unit = println("Hello")

// A function that takes one parameter of type String and returns Unit

def greet(name: String): Unit = println("Hello " + name)

// A function that takes two parameters of type Int and returns Int

def add(x: Int, y: Int): Int = x + y

// A function that takes two parameters of type Double and returns Double (return type omitted)

def multiply(x: Double, y: Double) = x * y

// A function that takes one parameter of type Int and returns String (body as a block)

def sign(n: Int): String =

if (n > 0) "Positive"

else if (n < 0) "Negative"

else "Zero"

// Function calls

greet() // prints Hello

greet("Alice") // prints Hello Alice

add(1, 2) // returns 3

multiply(3.14, 2) // returns 6.28

sign(-10) // returns Negative

In Scala,

In Scala, you can also define and use function literals, which are anonymous functions that can be assigned to values or variables, passed as arguments to other functions, or returned as results from other functions. The syntax of a function literal is (parameter: Type) => body. The parameter list can be empty or contain multiple parameters separated by commas. The body can be a single expression or a block of statements enclosed by curly braces.

// Function literals

// A function literal that takes no parameters and returns Unit

() => println("Hello")

// A function literal that takes one parameter of type String and returns Unit

(name: String) => println("Hello " + name)

// A function literal that takes two parameters of type Int and returns Int

(x: Int, y: Int) => x + y

// A function literal that takes two parameters of type Double and returns Double (parameter types omitted)

(x, y) => x * y

// A function literal that takes one parameter of type Int and returns String (body as a block)

(n: Int) =>

if (n > 0) "Positive"

else if (n < 0) "Negative"

else "Zero"

// Function literal usage

// Assigning a function literal to a value

val f = (x: Int) => x * x // f is a value of type Int => Int

// Calling a function literal

f(10) // returns 100

// Passing a function literal as an argument to another function

def apply(f: Int => Int, x: Int): Int = f(x) // apply is a higher-order function

apply(f, 10) // returns 100

apply((x: Int) => x + 1, 10) // returns 11

// Returning a function literal as a result from another function

def makeAdder(n: Int): Int => Int = (x: Int) => x + n // makeAdder is a higher-order function

val addOne = makeAdder(1) // addOne is a value of type Int => Int

val addTwo = makeAdder(2) // addTwo is a value of type Int => Int

addOne(10) // returns 11

addTwo(10) // returns 12

In Scala, you can use collections to store and manipulate multiple values of the same type. Scala provides many built-in collection types, such as arrays, lists, sets, maps, and more. Collections can be mutable or immutable, depending on whether they can be modified after creation or not. Immutable collections are preferred over mutable ones, as they are safer and easier to reason about.

One of the most common collection types in Scala is the list, which is an immutable sequence of values. You can create a list using the List object or the :: operator. You can access the elements of a list using the head and tail methods or the (index) syntax. You can also perform various operations on lists using methods such as map, filter, fold, and more.

// Lists

// Creating lists

val empty = List() // empty is an empty list

val nums = List(1, 2, 3) // nums is a list of three integers

val words = List("one", "two", "three") // words is a list of three strings

val mixed = List(1, "two", 3.0) // mixed is a list of three values of different types

val cons = 1 :: 2 :: 3 :: Nil // cons is another way to create a list of three integers

// Accessing list elements

nums.head // returns 1 (the first element)

nums.tail // returns List(2, 3) (the rest of the list)

nums(0) // returns 1 (the element at index 0)

nums(1) // returns 2 (the element at index 1)

nums(2) // returns 3 (the element at index 2)

// List operations

nums.length // returns 3 (the number of elements in the list)

nums.isEmpty // returns false (whether the list is empty or not)

nums.contains(2) // returns true (whether the list contains the value 2 or not)

nums.indexOf(2) // returns 1 (the index of the first occurrence of the value 2 in the list)

nums.reverse // returns List(3, 2, 1) (a new list with the elements in reverse order)

nums.map(x => x * x) // returns List(1, 4, 9) (a new list with each element transformed by the given function)

nums.filter(x => x % 2 == 0) // returns List(2) (a new list with only the elements that satisfy the given predicate)

nums.fold(0)(_ + _) // returns 6 (a single value obtained by combining all the elements using the given function)

Conclusion

In this article, we have given you an introduction to the art of programming using Scala. We have covered some of the basic concepts and features of Scala, such as expressions, types, values, variables, conditionals, functions, function literals, collections, and more. We have also shown you how to use the Scala tools, such as the REPL and scripts, to write and run Scala programs.

Scala is a versatile and expressive language that can help you master the art of programming. It supports multiple programming paradigms, such as functional and object-oriented programming, and allows you to write concise and elegant code. Scala is also a practical language that can be used for both small and large projects, as it runs on the JVM and interoperates with Java.

If you want to learn more about Scala and its advanced features, such as object-oriented design, abstract data types, traits, pattern matching, generics, implicits, and more, you can download the PDF version of this article for your reference. You can also check out some of the online resources and books on Scala listed below: