Programming Erlang, 2nd Edition

Maps: Associative Key-Value Stores

Maps were made available from version R17 of Erlang.

Maps have the following properties:

• The syntax of maps is similar to that of records, except the record name is omitted and the key-value separator is either => or :=.

• Maps are associative collections of key-value pairs.

• The keys in a map can be any fully ground Erlang term (fully grounded means that there are no unbound variables in the term).

• The elements in a map are ordered by the keys.

• Updating a map where the keys are not changed is a space-efficient operation.

• Looking up the value of a key in a map is an efficient operation.

• Maps have a well-defined order.

We’ll look at maps in more detail in the following sections.

The Semantics of Maps

Map literals ...