Map

val romanNumerals = Map("I" -> 1, "V" -> 5, "X" -> 10)

The syntax key -> value is just another way to write the pair (key, value).

• Map is the subclass of Iterable.

  romanNumerals.map((x, y) => (y, x))
  

• Map is function.

  romanNumerals("I") // 1
  

  However, it will throw an error if the key is not found. The better way to query is:

  romanNumerals.get("I") // Some(1)
  romanNumerals.get("aaa") // None
  

  Some and None are the subclass of Option.

Updating a Map

• m + (k -> v)
• m ++ kvs