haveMember

HaveMember is a term used in programming and formal specification to denote that a given element is a member of a container. In practice, it is often implemented as a predicate function or method, such as haveMember(collection, element), that returns a boolean indicating presence. The exact form and name vary by language, but the concept remains the same: testing whether the container contains the specified item.

Semantics and scope. HaveMember applies to a range of container types, including lists, arrays, and sets, and can also apply to maps or dictionaries to test the existence of a key. In many contexts, haveMember test for key existence rather than value presence in maps. The predicate typically returns true when the item is found and false otherwise. Some languages distinguish between membership tests for keys versus values; others treat containment uniformly across types.

Usage and examples. Typical usage patterns include checking for an element in a sequence or the presence of a key in a map. Examples: haveMember([1, 2, 3], 2) returns true; haveMember({apple: 3, banana: 5}, "apple") returns true; haveMember([1, 2, 3], 4) returns false. In many languages, equivalent operations are called contains, includes, or hasKey, depending on the container type.

Performance considerations. Time complexity depends on the container and its implementation. Linear scans occur for unsorted lists or arrays, while hash-based sets or maps yield average constant time for membership checks. Balanced trees offer logarithmic time.

See also. Related concepts include contains, includes, member, and membership operators in various languages.