Clojure - Values and Change: Clojure’s approach to Identity and State

BRANK

OO is, among other things, an attempt to provide tools for modeling identity and state in programs (as well as associating behavior with state, and hierarchical classification, both ignored here). OO typically unifies identity and state, i.e. an object (identity) is a pointer to the memory that contains the value of its state. There is no way to obtain the state independent of the identity other than copying it. There is no way to observe a stable state (even to copy it) without blocking others from changing it. There is no way to associate the identity’s state with a different value other than in-place memory mutation. In other words, typical OO has imperative programming baked into it! OO doesn’t have to be this way, but, usually, it is (Java/C++/Python/Ruby etc).People accustomed to OO conceive of their programs as mutating the values of objects. They understand the true notion of a value, say, 42, as something that would never change, but usually don’t extend that notion of val…