Language List

empty_list = []
one_item_list = [1]
two_item_list = [1, 2]
multiple_type_list = [1, :pi, 3.14, "four"]

# [1] represented in [head | tail] notation
[1 | []]

# [1, 2, 3] represented in [head | tail] notation
[1 | [2 | [3 | []]]]

# Suppose
list = [2, 1]

[3, 2, 1] == [3 | list]
# => true

# Check if 1 is a member of the list
1 in [1, 2, 3, 4]
# => true

Instructions

In this exercise you need to implement some functions to manipulate a list of programming languages.

1. Define a function to return an empty language list

Define the new/0 function that takes no arguments and returns an empty list.

LanguageList.new()
# => []

2. Define a function to add a language to the list

Define the add/2 function that takes 2 arguments (a language list and a string literal of a language). It should return the resulting list with the new language prepended to the given list.

language_list = LanguageList.new()
# => []
language_list = LanguageList.add(language_list, "Clojure")
# => ["Clojure"]
language_list = LanguageList.add(language_list, "Haskell")
# => ["Haskell", "Clojure"]

3. Define a function to remove a language from the list

Define the remove/1 function that takes 1 argument (a language list). It should return the list without the first item. Assume the list will always have at least one item.

language_list = LanguageList.new()
# => []
language_list = LanguageList.add(language_list, "Clojure")
# => ["Clojure"]
language_list = LanguageList.add(language_list, "Haskell")
# => ["Haskell", "Clojure"]
language_list = LanguageList.remove(language_list)
# => ["Clojure"]

4. Define a function to return the first item in the list

Define the first/1 function that takes 1 argument (a language list). It should return the first language in the list. Assume the list will always have at least one item.

language_list = LanguageList.new()
# => []
language_list = LanguageList.add(language_list, "Elm")
# => ["Elm"]
language_list = LanguageList.add(language_list, "Prolog")
# => ["Prolog", "Elm"]
LanguageList.first(language_list)
# => "Prolog"

5. Define a function to return how many languages are in the list

Define the count/1 function that takes 1 argument (a language list). It should return the number of languages in the list.

language_list = LanguageList.new()
# => []
language_list = LanguageList.add(language_list, "Elm")
# => ["Elm"]
language_list = LanguageList.add(language_list, "Prolog")
# => ["Prolog", "Elm"]
LanguageList.count(language_list)
# => 2

6. Define a function to determine if the list includes a functional language

Define the functional_list?/1 function which takes 1 argument (a language list). It should return a boolean value. It should return true if "Elixir" is one of the languages in the list.

language_list = LanguageList.new()
# => []
language_list = LanguageList.add(language_list, "Elixir")
# => ["Elixir"]
LanguageList.functional_list?(language_list)
# => true