Functions for working with tuples.

Tuples are ordered collections of elements; tuples can contain elements of any type, and a tuple can contain elements of different types. Curly braces can be used to create tuples:

iex> {}
{}
iex> {1, :two, "three"}
{1, :two, "three"}

Tuples store elements contiguously in memory; this means that accessing a tuple element by index (which can be done through the Kernel.elem/2 function) is a constant-time operation:

iex> tuple = {1, :two, "three"}
iex> elem(tuple, 0)
1
iex> elem(tuple, 2)
"three"

Same goes for getting the tuple size (via Kernel.tuple_size/1):

iex> tuple_size({})
0
iex> tuple_size({1, 2, 3})
3

Tuples being stored contiguously in memory also means that updating a tuple (for example replacing an element with Kernel.put_elem/3) will make a copy of the whole tuple.

Tuples are not meant to be used as a “collection” type (which is also suggested by the absence of an implementation of the Enumerable protocol for tuples): they’re mostly meant to be used as a fixed-size container for multiple elements. For example, tuples are often used to have functions return “enriched” values: a common pattern is for functions to return {:ok, value} for successful cases and {:error, reason} for unsuccessful cases. For example, this is exactly what File.read/1 does: it returns {:ok, contents} if reading the given file is successful, or {:error, reason} otherwise (e.g., {:error, :enoent} if the file doesn’t exist).

This module provides functions to work with tuples; some more functions to work with tuples can be found in Kernel (Kernel.tuple_size/1, Kernel.elem/2, Kernel.put_elem/3, and others).