other stuff

Question 1

Curried function form

Answer 1

A ⇒ (B ⇒ C) = (A)(B) ⇒ C

Question 2

Uncurried function form

Answer 2

(A,B) ⇒ C

Question 3

First-class functions

Answer 3

treated like any other value

Question 4

lazy val

Answer 4

computed once, when value is first used, reuses value afterwards

Question 5

def

Answer 5

computed each time when value is used

Question 6

val

Answer 6

computed once, when object is created, reuses value afterwards

Question 7

closure

Answer 7

has free parameters ( which can be modified inside it)

Question 8

generic classes

Answer 8

take types as a parameter

Question 9

abstract

Answer 9

needs to be extended
Cannot instantiateabstract classes directly
Abstract methodsmust be implemented by subclasses
Supportspolymorphismand code reuse through inheritance

Question 10

null

Answer 10

a subtype of any (+user defined) class

Question 11

final

Answer 11

cannot be overridden or redefined in subclasses
No subclasses possible

Question 12

super

Answer 12

use super keyword to call the immediate parent class’ method

Question 13

any

Answer 13

Every class in a Scala execution environment inherits directly or indirectly from this class

Question 14

Overloading

Answer 14

ability to redefine a function in more than one form, by defining two or more functions in a class sharing the same name
sum(a,b,c) <-> sum(a,b)

Question 15

LUB

Answer 15

the lowest common ancestor

Question 16

exists
x.exists(p)

Answer 16

a boolean indicating whether the predicate p holds for some element in x

Question 17

forall
x.forall(p)

Answer 17

a boolean indicating whether the predicate p holds for all elements of x

Question 18

count
x.count(p)

Answer 18

the number of elements in x that satisfy the predicate p

Question 19

takewhile
x.takeWhile(p)

Answer 19

The longest prefix of elements in the collection that all satisfy p

Question 20

dropwhile
x.dropWhile(p)

Answer 20

The collection without the longest prefix of elements that all satisfy p

Question 21

x.foreach(f)

Answer 21

executes function f for each element of x

Question 22

x.map(f)

Answer 22

the collection obtained from applying the function f to every element in x

Question 23

desugaring
loop ->
yield ->
yield with multiple indices ->

Answer 23

foreach
map, filter
flatmap

Question 24

x.filter(p)

Answer 24

collection consisting of those elements of x that satisfy the predicate p

Question 25

x.flatMap(f)

Answer 25

collection obtained from applying the collection-valued function f to every element in x and concatenating the results

Question 26

xs.foldLeft(z)(op)

Answer 26

Apply binary operation op between successive elements of xs, going left to right and starting with z

Question 27

xs.foldRight(z)(op)

Answer 27

Apply binary operation op between successive elements of xs, going right to left and starting with z.

Question 28

monoid

Answer 28

a set and an associated binary oeprator that combines two elements from the set
def[A] |+| (left: A, right: A): A

Question 29

zipWithIndex

Answer 29

return a set of tuples (element, index)

Question 30

Nothing

Answer 30

has no values
is a subtype of everyhing

Question 31

Linear pattern

Answer 31

each variable occurs only once

Question 32

Sealed classes

Answer 32

No extension of the class is possible outside of the current file
If a function is not sealed, it needs a default case or you will get a warning: match is not exhaustive!
-> allows exhaustive pattern matching

Question 33

Option

Answer 33

be either Some[T] or None object, which represents a missing value

Question 34

Tail Recursion

Answer 34

he recursive call is the last thing done by the function

Question 35

Static typing

Answer 35

check types at compile time, without running the code

Question 36

Dynamic typing

Answer 36

check types at runtime, while running the code

Question 37

:<
A :< B

Answer 37

specifies an upper bound
B is upper bound of A

Question 38

traits

Answer 38

like an abstract class
a class can extend multiple traits (but one class)
a trait also defines a type

Question 39

Diamond problem

Answer 39

occurs whenever we have some type of multiple inheritance

Question 40

Linearisation

Answer 40

• Searched in linear order for method implementation:
  Deepest first, last trait first

Question 41

COVARIANCE
If A:B =>

Answer 41

COVARIANCE
→ more specific output
=> then I<a> : I<b></b></a>

(if A is a subtype of B)

Question 42

CONTRAVARIANCE
If A:B then =>

Answer 42

→ more general input

=> I<b> : I<a></a></b>

Question 43

INVARIANCE

Answer 43

input and output

Question 44

variance of:
lists
arrays
seq

Answer 44

covariant
contravariant
covariant

Question 45

function subtyping
A ⇒ B

Answer 45

functions are contravariant in their arguments but covariant in their results
general ⇒ specific