mapget

Mapget is a term used in programming to describe retrieving the value associated with a key from a map, dictionary, or associative array. It is a fundamental operation in data structures that store key-value pairs, enabling fast lookups when the key is known.

Semantics and behavior: When the key exists, mapget returns the corresponding value. If the key is absent, languages differ: some return a default value or null, others throw an exception, and some provide a separate method to test for membership before retrieval. These differences influence error handling and control flow.

Variations: Many languages implement mapget as part of standard libraries or as a convenience function. A safe variant often called getOrDefault or withDefault supplies a user-specified default when the key is missing. Some APIs distinguish between non-strict lookups and strict lookups that signal absence.

Performance: The time to mapget depends on the map implementation. In hash-based maps, average time is constant, O(1). In tree-based maps, it is O(log n). The space cost is the size of the map plus overhead for missing-key handling.

Language examples: In Python, dict.get(key, default) provides a default when the key is missing. In Java, Map.get(key) returns the value or null if not present. In JavaScript, Map.prototype.get(key) returns undefined for absent keys. These examples show how mapget appears across ecosystems.

See also: dictionary, associative array, hash table, lookup, default value.