FP

Question 1

def assertAllPosS <: IntSet: S = …

Here what [S <: IntSet] is ?

And what does that mean ?

Answer 1

S is a subtype of Intset.We can also say that type S is upperbounded by type IntSet

It means that S can be instantiated only to types that conform to IntSet.

Question 2

What is Liskov Substituion Principle

Answer 2

When one can to do with a value of type B
one should also be able to do with a value of type A.

Eg: Everything we can do with a fruit, we can do with a banana. Everything we can do with an animal, we can do with a Cat and so on…

Question 3

How is Covariance and Contravariance denoted in Scala

Answer 3

With a “+” or a “-“ next to the Parametric Type.

Example:

class Box+T

Question 4

What is Covariance ?

Answer 4

Covariance allows a generic type to preserve the subtype relationship. In other words, if type B is a subtype of type A, then Container[B] is a subtype of Container[A].

Question 5

Why is Covariance useful ?

Answer 5

This is useful in situations where you want to create collections or structures that can hold more specific types but still be treated as holding more general types.

Question 6

What is Contravariant ?

Question 7

Why is Contravariant useful ?

Answer 7

This is useful when you’re consuming values but not producing them. For example, let’s say you have a function that can accept any type of Animal, but you want to pass in a more general handler that can accept Dogs or Cats.

Question 8

what is type parameterization ?

Answer 8

When we say a class, trait, or method is type parameterized, it means that it can accept a type as a parameter (called a type parameter) that gets specified later, when you create an instance of the class or call the method.

Question 9

In the contexte of Polymorphisme what are bounds ?

Answer 9

Bounds are constraints from subtypes applied to types parameters.

Question 10

in the context of Polymorphisme what is Variance ?

Answer 10

How type parameters behaves when subtyping occurs.

Question 11

What a is a generic type ?

Answer 11

A generic type (or type parameterization) is a type that is defined with one or more type parameters, allowing it to work with different types without specifying the exact types in advance. It provides a way to write reusable and flexible code that can operate on various data types while maintaining type safety at compile-time.

Question 12

What is a generic class ?

Answer 12

A class that is defined with one or more type parameters, allowing it to work with different types without having to specify those types exactly in advance

Eg: A List

Question 13

What is the difference and the relation between a class and a type

Answer 13

Une classe est une définition ou une description d’un objet. Elle décrit comment un objet est construit et comment il se comporte. Elle est souvent associée à la création d’instances (objets) et contient des méthodes et des champs.

Un type est une catégorie de données qui décrit les valeurs que peut prendre une variable. Il peut être défini par une classe (comme Person), mais il peut également être autre chose (comme un type primitif ou un type abstrait).

Question 14

Among Arrays and list which one are covariant which one isn’t and why ?

Answer 14

Arrays aren’t covariant because they are mutable while list are not mutable. Since you cannot modify the list, you can’t accidentally add a Cat to a list of Dogs.

Question 15

What are the typing rules for function ?

Answer 15

if A2> A1 and B>B2 then
A1 => B1 < A2 => B2

Question 16

how functions behaves in terms of variance regarding their type arguments and their return type

Answer 16

function are contravariant in their argument and covariant in their result type

Question 17

Can Objects have parameters. If yes or no why ?

Answer 17

They can’t because there’s only one instance of an object

Question 18

What is Nothing in Scala ?

Answer 18

It’s a universal subtype of all types

Question 19

What is a trait ?

Answer 19

A trait is like an interface in other languages (such as Java), but it can also include method implementations. It is primarily used to define behavior that can be shared across different classes. Traits are commonly used for multiple inheritance of behavior.

trait CanFly {
def fly(): Unit = println(“Flying”)
}

trait CanSwim {
def swim(): Unit = println(“Swimming”)
}

class Duck extends Animal with CanFly with CanSwim

Question 20

What is a coefficient

Answer 20

A number that mutiplies an other. That is a subtype of a factor ( number only)

Question 21

What is a polynomial ?

Answer 21

A mathematical expression composed of variables (unknowen) and coefficient that are linked by operations ( somme, soubrstration, etc.). Les variables dans un polynôme sont élevées à des puissances non négatives (entiers naturels).

Question 22

What is factorize ?

Answer 22

Factoriser consiste à réécrire une expression mathématique sous la forme d’un produit de plusieurs facteurs

Question 23

What is a factor

Answer 23

Term or expression mutiplied by a term or a an expression

Question 24

What are the steps of solving a recursion ?

Answer 24

Step1: Find the base case
Step2: Visualize
Step 3: Relate (bigger example with smaller example )
Step 4: Generalize
Step 5: Write code
step 6: substitution method

Question 25

Quelle expression logique, je peux utiliser pour trouver les nombres impairs d’une liste ?

Answer 25

(l.head % 2 != 0)

Question 26

Comment appelle-t-on le fait que “tous les éléments d’un ensemble respectent une condition” est considéré comme vrai même si l’ensemble est vide ?

Answer 26

Réponse : Vérité triviale (ou quantificateur universel sur un ensemble vide).

Question 27

What function function check if an element is present in a list? What argument does it take, what does it return ?

Answer 27

The contains function checks if a given element exists in a list. If the element is found, it returns true; otherwise, it returns false.

Question 28

What is the difference between a set and a list

How can you find stuff in a list vs in a set

Answer 28

Set: Ideal for collections where the uniqueness of elements is important and frequent lookups are necessary.
List: Used when the order of elements or the possibility of duplicates is important, or for sequential processing operations.
list use a Linkedlist method, while set use a hash method where an inex represent one element

Question 29

How can you find stuff

Question 30

What a function return an expression of this form:

x || y

What appens

Answer 30

L’évaluation s’arrête dès que True et retourner pour la première partie gauche de l’opérateur car si c’est true cela sera toujours true.

Question 31

What is a literal ?

Answer 31

A literal is a fix value without a name

Question 32

What is a constant ?

Answer 32

A constant is a fix value with a name

Question 33

What is the opposite of a literal ?

Answer 33

The opposite is a calculated variable or a dynamic variable that are generetated at the execution of the program.

Question 34

Enum

Answer 34

Un enum en Scala est un type qui permet de définir un ensemble fixe et limité de valeurs nommées (ou cas), souvent utilisé pour représenter des choix ou des états constants dans un programme.

Question 35

What are algebraic Data Structures

Answer 35

Les types de données algébriques (ou ADTs) sont des types composites qui combinent des valeurs simples en structures complexes, utilisant deux opérations principales : les types produits (ET) pour combiner plusieurs valeurs obligatoires, et les types sommes (OU) pour représenter des choix exclusifs parmi plusieurs options.

Question 36

What is a product type in the context of aglbraic data structures ?

Answer 36

An agebraic data types where all values are obligatory eg:
case class Adresse(rue: String, codePostal: String, ville: String)

Question 37

What is a sum type in the context of agebraic data structures ?

Answer 37

A data structure that can be either on or an other:

Eg:

sealed trait Animal
case class Chien(nom: String) extends Animal
case class Chat(nom: String) extends Animal

Question 38

Quel est ce symble ? &

Answer 38

C’est un bitwise AND.

Il compare chaque bit de deux nombres binaires et revoit uniquement des 1 si c’est 1 des dans les deux nombres.

Question 39

What is final class

Answer 39

it’s a class that can not be extended to other class ( not inherited)

Question 40

Que fait la fonction count ?

Answer 40

a fonction count retourne le nombre d’éléments dans une collection qui satisfont une condition donnée (un prédicat).

a fonction count retourne le nombre d’éléments dans une collection qui satisfont une condition donnée (un prédicat).

Question 41

Que fait lenght

Answer 41

La fonction length retourne le nombre total d’éléments dans une collection.

val words = List(“apple”, “banana”, “cherry”)
words.length // Résultat : 3 (nombre total de mots)

Question 42

When can Reduce been used in parralele

Answer 42

When the op is associative.
When we say that an operator op must be associative, we mean that it should yield the same result regardless of how the elements are grouped

Question 43

l.scanLeft(z)(op) == l.reverse.scanRight(z)((a, b) ⇒ op(b, a)).reverse