Transient data structures

Transients are mutable builders for Vector, Map, Set, SortedVector, DoubleVector, and IntVector. Operations ending in ! mutate the builder; persistent! returns an immutable value and invalidates the transient. The original persistent collection is never changed.

with-mutable scopes that lifecycle and returns the persistent result automatically:

(def original [1 2 3])
(def updated
  (with-mutable [builder original]
    (conj! builder 4)))

original ; => [1 2 3]
updated  ; => [1 2 3 4]

The available mutation operations and Python-compatible mutable APIs vary by transient type. See transient operations in the standard library reference for the complete API and interoperability examples.