View Source Lists and Tuples
Elixir has two collection types: (Linked) Lists and Tuples.
Lists
A List is defined with square brackets and can contain elements of different data types:
details = ["Peter", 32, 190.47, true, :active]Lists are not stored contiguously in memory because they are implemented as linked lists. Each element is stored in memory with its value and a pointer to the next element. This structure makes traversing, updating, deleting, and appending values slow, but prepending new values fast. For more information, see the Big-O Time Complexities section.
You can access elements in various ways:
details = ["Peter", 32, 190.47, true, :active]
# Get the 2nd element, because lists are 0-based.
Enum.at(details, 1) # => 32
# Get the last element with a negative index
Enum.at(details, -1) # => :active
# Or use the `List` helper functions
List.first(details) # => "Peter"
List.last(details) # => :active
# Update an element at a specific index
List.replace_at(details, 1, 30)
# => ["Peter", 30, 190.47, true, :active]
# Prepend a value to the list
[:adult | details]
# => [:adult, "Peter", 32, 190.47, true, :active]
# Concatenate two lists
details ++ [nil, 123]
# => ["Peter", 32, 190.47, true, :active, nil, 123]
# Delete the first occurrence of an element
List.delete(details, 32)
# => ["Peter", 190.47, true, :active]
# Delete an element at a specific index
List.delete_at(details, -1)
# => ["Peter", 32, 190.47, true]Tuples
A Tuple is stored contiguously in memory. That makes accessing an element by its index or getting the tuple size a fast operation.
hobbies = {"Sport", "Coffee", "Writing"}
# Get the first element
elem(hobbies, 0) # => "Sport"
# Update an element
put_elem(hobbies, 2, "Reading")
# => {"Sport", "Coffee", "Reading"}
# Append an element
Tuple.append(hobbies, "Coding")
# => {"Sport", "Coffee", "Writing", "Coding"}
# Delete an element at a specific index
Tuple.delete_at(hobbies, 1)
# => {"Sport", "Writing"}
# Get the Tuple size
tuple_size(hobbies) # => 3If you look closely at the output above, you'll see that although we update and append elements to our tuple, the original hobbies variable is not modified. In Elixir, variables are immutable and every function call => a copy of the input variable instead of a modified version of the original variable.