Scala for Backend Engineering & Functional Programming · Leçon

Syntaxe et types de base

Comprenez la syntaxe fondamentale de Scala, les déclarations de variables (val/var), les types de données courants et les opérateurs de base.

Syntaxe et types de base est une leçon Scala for Backend Engineering & Functional Programming gratuite sur CoddyKit. Ceci est la leçon 2 sur 3. Tu peux lire la leçon complète ci-dessous gratuitement — puis la pratiquer en direct dans le navigateur avec un éditeur de code intégré et un tuteur IA 24/7. Elle fait partie du parcours d'apprentissage Scala for Backend Engineering & Functional Programming, et ta progression se synchronise sur le web et l'application CoddyKit. Le cours Scala for Backend Engineering & Functional Programming comprend 3 leçons au total.

Certaines parties de cette leçon n'ont pas encore été traduites et s'affichent en anglais.

Scala's Clean Syntax

Welcome to Scala's basic syntax! Scala is designed to be concise and expressive, often allowing you to write less code to achieve more.

Unlike some languages, semicolons are usually optional at the end of a line if there's only one statement. This helps keep your code clean.

Expressions Are Key

In Scala, almost everything is an expression, meaning it evaluates to a value. This is a powerful concept that makes your code more functional and predictable.

Even a simple calculation or a conditional block can return a value.

Try running this example:

object Main {
  def main(args: Array[String]): Unit = {
    val x = 5 + 3
    println(s"The value of x is: $x")

    val message = if (x > 7) "Greater than 7" else "Not greater than 7"
    println(message)
  }
}

`val`: Immutable Values

When you declare a variable using val, you are creating an immutable value. This means once it's assigned, its value cannot be changed.

Immutability is a cornerstone of functional programming and helps prevent unexpected side effects, making your code safer and easier to reason about.

Try it out:

object Main {
  def main(args: Array[String]): Unit = {
    val greeting = "Hello, Coddy!"
    println(greeting)
    // greeting = "New message" // This would cause a compile error!
  }
}

`var`: Mutable Variables

Sometimes you need a variable whose value can change. For this, Scala provides var for mutable variables.

While useful, it's a good practice in Scala to favor val over var whenever possible to embrace immutability and functional style.

See how `var` works:

object Main {
  def main(args: Array[String]): Unit = {
    var counter = 0
    println(s"Initial counter: $counter")
    counter = counter + 1
    println(s"New counter: $counter")
  }
}

Numbers: Int, Long, Double

Scala supports common numeric types. The compiler often infers the type, but you can specify it.

Int: For whole numbers (e.g., 10)
Long: For larger whole numbers (suffix L, e.g., 10000000000L)
Double: For floating-point numbers (decimals, e.g., 3.14)

Here's an example:

object Main {
  def main(args: Array[String]): Unit = {
    val anInt = 42
    val aLong = 1234567890123L
    val aDouble = 3.14159

    println(s"Int: $anInt")
    println(s"Long: $aLong")
    println(s"Double: $aDouble")
  }
}

Boolean and Char Types

Beyond numbers, Scala has types for truth values and single characters:

Boolean: Represents truth values, either true or false.
Char: Stores a single character, enclosed in single quotes (e.g., 'A').

These are fundamental for logic and text processing.

Example:

object Main {
  def main(args: Array[String]): Unit = {
    val isActive = true
    val initial = 'C'

    println(s"Is active? $isActive")
    println(s"Initial character: $initial")
  }
}

Strings and Text

The String type is used for sequences of characters, or text. Strings are immutable in Scala, just like in Java.

A very useful feature is String Interpolation, which allows you to embed expressions directly within string literals using an s prefix and $ for variables.

Check this out:

object Main {
  def main(args: Array[String]): Unit = {
    val name = "Coddy"
    val age = 3

    val greeting = s"Hello, my name is $name and I am $age years old."
    println(greeting)

    val mathResult = s"Two plus two is ${2 + 2}"
    println(mathResult)
  }
}

Basic Arithmetic Operators

Scala provides standard arithmetic operators for performing calculations with numbers:

+ (Addition)
- (Subtraction)
* (Multiplication)
/ (Division)
% (Modulo - remainder of division)

These operators work as you'd expect, returning a new numeric value.

Let's do some math:

object Main {
  def main(args: Array[String]): Unit = {
    val a = 10
    val b = 3

    println(s"Addition: ${a + b}")
    println(s"Subtraction: ${a - b}")
    println(s"Multiplication: ${a * b}")
    println(s"Division: ${a / b} (integer division)")
    println(s"Modulo: ${a % b}")

    val c = 10.0
    val d = 3.0
    println(s"Float Division: ${c / d}")
  }
}

Comparison Operators

Comparison operators are used to compare two values and always return a Boolean (true or false).

== (Equal to)
!= (Not equal to)
< (Less than)
> (Greater than)
<= (Less than or equal to)
>= (Greater than or equal to)

They are essential for control flow and decision-making.

object Main {
  def main(args: Array[String]): Unit = {
    val x = 10
    val y = 5

    println(s"x == y: ${x == y}")
    println(s"x != y: ${x != y}")
    println(s"x > y: ${x > y}")
    println(s"x <= y: ${x <= y}")
  }
}

Quick Check: Variables & Operators

Consider the following Scala code snippet:

object Main {
  def main(args: Array[String]): Unit = {
    val num1 = 7
    var num2 = 3
    num2 = num1 * 2
    val finalResult = num1 + num2 - 5
    println(finalResult)
  }
}

Recap: Syntax & Types

Great job! In this lesson, you've learned the fundamentals of Scala's basic syntax, including the use of expressions and the optional nature of semicolons.

We explored how to declare variables using val for immutable values and var for mutable ones. You also got familiar with common data types like Int, Long, Double, Boolean, Char, and String, including handy String Interpolation.

Finally, you practiced using basic arithmetic and comparison operators to perform calculations and logical checks. Keep practicing these basics as they are the building blocks for more complex Scala programs!

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