immutabel

Immutabel is a concept in computer science describing data or objects whose state cannot be changed after creation. In practice, immutabel objects enforce a fixed value and operations that would alter the state instead produce a new object with the updated state. The term is closely related to immutable, but immutabel is sometimes used as a stylized or localized spelling in programming discussions or documentation.

Achieving immutabel state typically relies on data structures designed to be persistent, such as linked lists, trees, or maps that share most of their structure between versions. Copy-on-write and structural sharing minimize allocations. Many functional languages (Haskell, Erlang, Clojure) treat immutabel data as the default, while languages with mutable references (JavaScript, Python, Java) support immutabel usage through immutable types, frozen objects, or careful programming discipline.

Common examples include strings in many languages, tuples in Python and other languages, and records defined as frozen or read-only. In practice, immutabel objects enable safer concurrent execution, easier reasoning about code, and straightforward undo/redo semantics, as previous states remain accessible.

Trade-offs include potential performance costs from creating new objects rather than updating in place and increased memory usage in naïve implementations. However, modern techniques mitigate these costs through sharing and specialized allocators.

Origin and terminology: the root is the Latin immutabilis meaning not changeable; the English term immutable is standard, with immutabel appearing in some dialects or discussions. See also immutable, persistent data structures, structural sharing, copy-on-write.