Pascal-Chapter Lists

Chapter 11 : Lists and Sets

Please now plot our course as a list of destinations.

Lists are linear collections of elements of the same type. Linear means that, in order to reach an element in a list, we must visit all the elements before (sequential access). Elements can be repeated, as only their order in the collection matters. The first element is called the head, and the sub-list after the head is called the tail.

Lists

To define an empty list :

const empty_list : list (int) = list []

ℹ️ You can also use nil instead of list []

To define list with values:

const my_list : list (int) = list [122]

You can add elements to an existing list using the cons operator # :

const larger_list : list (int) = 5 # my_list // [5; 1; 2; 2]

or

const larger_list : list (int) = cons(5, my_list) // [5; 1; 2; 2]

Sets

Sets are unordered collections of values of the same type, like lists are ordered collections. Elements of sets in LIGO are unique, whereas they can be repeated in a list. To define a set :

const my_set : set (int) = set [3221]

You can test membership with the contains operator :

const contains_3 : bool = my_set contains 3

You can get the size of a set using the Set.size operator :

const cardinal : nat = Set.size (my_set)

To update a set :

const larger_set : set (int) = Set.add (4, my_set)
const smaller_set : set (int) = Set.remove (3, my_set)

Your mission

1- Define a variable itinary as a list of string names of celestial bodies representing your course. Start with “earth”

2- On the next line, add “sun” to the itinary.

2- On the next line, add “alpha-centauri” to the itinary.

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