Language List

$no_keys = ["my", "first", "array"];
$integer_keys = [0 => "my", 1 => "first", 2 => "array"];

$no_keys == $integer_keys // => equal returns true
$no_keys === $integer_keys // => strictly equal returns true

$prime_numbers = [2, 3, 5, 6];

$prime_numbers[3] = 7; // replace 6 with 7

$prime_numbers[] = 11; // array now contains [2, 3, 5, 7, 11]

<?php

function actOnItems(...$items) {
  // $items is an array containing 0 or more values
  // used to call the function.
}

actOnItems(1, 2, 3, 4); // $items => [1, 2, 3, 4]

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 language_list function that takes no arguments and returns an empty list.

<?php

language_list();
// => []

2. Modify function to create a list from any number of languages

Modify the language_list function, so it takes a variadic argument of languages (strings). It should return the resulting list with the languages in the list.

<?php

$language_list = language_list();
// => []
$language_list = language_list("Clojure", "PHP");
// => ["Clojure", "PHP"]
$language_list = language_list("PHP", "Haskell", "Java", "C++", "Rust")
// => ["PHP", "Haskell", "Java", "C++", "Rust"]

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

Define the add_to_language_list function that takes 2 arguments, an array of languages, and the new language.

<?php

$language_list = language_list();
// => []
$language_list = add_to_language_list($language_list, "Clojure");
// => ["Clojure"]

4. Define a function to remove an item from the language list

Define the prune_language_list function to remove the first language from the array of languages.

<?php

$language_list = language_list("PHP");
// => ["PHP"]
$language_list = prune_language_list($language_list);
// => []

5. Define a function to get the first item in the list

Define the current_language 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.

<?php

$language_list = language_list("PHP", "Prolog");
// => ["PHP", "Prolog"]
$first = current_language($language_list);
// => "PHP"

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

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

<?php

$language_list = language_list("PHP", "Prolog", "Wren");
// => ["PHP", "Prolog", "Wren"]
language_list_length($language_list);
// => 3