Dictionary

An ADT that contains a collection of (key, value) pairs, such that each key appears at most once in the collection.¹

Also known as associative arrays.

Properties

• mutable length
  • you set as many (key, value) pairs as you like, but keys must be unique
• keys must be unique
  • if it isn’t, you are effectively overwriting the original value
• pairs are unordered
  • programming languages may provide ordered solutions e.g. OrderedDict vs dict in Python

Signature

name: Dictionary
import: key, value, integer, boolean
operators:
  newDict: -> Dictionary;
  insert: Dictionary × key × value -> Dictionary;
  inDict: Dictionary × key -> boolean;
  remove: Dictionary × key -> Dictionary;
  lookup: Dictionary × key -> value;
  update: Dictionary × key × value -> Dictionary;
  length: Dictionary -> integer;

Footnotes

1. https://en.wikipedia.org/wiki/Associative_array ↩