Programming Elixir 1.2

Double-Quoted Strings Are Binaries

Whereas single-quoted strings are stored as char lists, the contents of a double-quoted string (dqs) are stored as a consecutive sequence of bytes in UTF-8 encoding. Clearly this is more efficient in terms of memory and certain forms of access, but it does have two implications.

First, because UTF-8 characters can take more than a single byte to represent, the size of the binary is not necessarily the length of the string.

iex> dqs = "∂x/∂y"
"∂x/∂y"
iex> String.length dqs
5
iex> byte_size dqs
9
iex> String.at(dqs, 0)
"∂"
iex> String.codepoints(dqs)
["∂", "x", "/", "∂", "y"]
iex> String.split(dqs, "/")
["∂x", "∂y"]

Second, because you’re no longer using lists, you need to learn ...