Putset

Putset is a term encountered in some computer science writings to refer to a set‑like collection that emphasizes its insertion operation. There is no universally accepted definition, and usage varies by author and context. In many descriptions, a putset provides at least a put(x) operation to insert elements, a membership test like contains(x), and a way to iterate over stored elements. Typically, putsets aim to store unique elements, so inserting an existing item does not create duplicates.

Variants differ in aspects such as ordering and mutability. Some putsets preserve insertion order, yielding elements in the sequence they were added; others do not guarantee any particular order. Implementations may be mutable, modifying the existing collection in place, or persistent/immutable, returning a new putset with the added element while leaving the original unchanged. Performance characteristics (time for put, contains, and iteration) depend on the underlying data structure, such as hash-based or tree-based representations.

Common use cases described in literature include modeling repositories of unique items, such as identifiers, tags, or tokens, where duplicates must be avoided and membership checks are frequent. In these discussions, putset is often contrasted with generic sets that may emphasize different operation names (for example, add vs put) or with multisets that allow duplicates.

Etymology derives from combining “put,” the insertion action, with “set,” the mathematical concept of a collection of unique elements. Because the term appears in niche contexts, its precise semantics should be taken from the specific source in which it is used. See also set, hash set, insertion-ordered set, and map.