getLastOrDefault

getLastOrDefault is a function or method found in various programming libraries that returns the last element of a sequence or collection, or a user-provided default value if the sequence is empty. The pattern is common in functional and query-style APIs to avoid exceptions when accessing the last element of a potentially empty collection.

Signature and variations typically describe a last-element retrieval with a fallback. A common form is getLastOrDefault<T>(IEnumerable<T> source, T defaultValue), where source is the sequence and defaultValue is returned if the sequence has no elements. Some implementations also support additional overloads, such as applying a selector or predicate before selecting the last element, or supplying a custom default value provider.

Key behavior considerations include the need for a defined order. The concept of "last" depends on an ordering of elements, which is usually the insertion or natural order of the sequence. If the source is empty, the function returns the supplied default value; if the source is non-empty, the value returned is the final element in that order. In some languages, a variant without an explicit default returns a language-specific default (for example, null or zero) when the sequence is empty, or may throw an exception.

Edge cases and performance notes: empty collections yield the default value; null inputs may raise an exception in many APIs. The time complexity to obtain the last element is typically O(n) for streams or enumerables that cannot directly access the end, but can be O(1) for indexed collections that store a last element.

Related concepts include the standard LastOrDefault or LastOrDefault-like utilities in other libraries, as well as first-or-default variants for retrieving the first element with a fallback.