Optionalmap

Optionalmap is a data structure in computer science that blends the concepts of a map with optional values. It represents a mapping from keys to values where the value itself can be present or absent. In other words, each key may be associated with a value (some value) or with no value (none), and some designs also allow a key to be completely absent from the mapping. This combination enables explicit representation of partial data, where the absence of a value conveys information beyond mere missing keys.

Semantics of an Optionalmap vary by implementation. Some designs treat a missing key as distinct from a key that exists but maps to None, offering a containsKey (or hasKey) operation to distinguish presence from absence. Others expose retrieval operations that return a nested optional type, such as an optional value wrapped in another optional, requiring additional unwrapping to determine both the presence of the key and the presence of a value.

Common operations on an Optionalmap include insertion and update of entries, removal of keys, and lookup. Typical APIs provide get, put, and remove, along with utilities such as containsKey, getOrDefault, and map or fold-style traversals. Merging two Optionalmaps, filtering by keys or values, and transforming the value type through mapping are also supported in many implementations.

Use cases for Optionalmap include representing configuration parameters where some fields may be unspecified, modeling partial records in databases, managing feature flags with optional metadata, and implementing sparse data structures where many keys are not assigned a value.

Related concepts include standard maps, optional types (Maybe/Option), and partial functions. Optionalmap serves as a pragmatic bridge when both key presence and value absence carry meaningful information.