A reimplementation of the stateful transducers from clojure.core, in a way that opens their states to extension.
Suppose you want to use stateful transducers in a context in which you need control over their states, for example to persist their states to disk and restore them.
If you try to do this with the ones in clojure.core, you will run into a snag: they construct their states themselves in a lexical scope, usually a value in a volatile!, sometimes a java collection... not something that is easy for you to extend from Clojure.
If volatile! were a dynamic function, then you could replace its implementation in order to manage the transducer's state yourself.
Since it is not, there is no straightforward way to access a transducer's state, unless the transducer is implemented to allow this. They generally are not open to this sort of extension. The functions in clojure.core which return stateful transducers are not. Replicas of all of them are provided in this library (only the arity that returns the stateful transducer).
Their implementations are trivially different from those in clojure.core. The main difference is that instead of calling volatile! to construct their state, they call a dynamic function coddled-super-centaurs.core/*state* and expect it to return a volatile!. Also, instead of a java.util.ArrayList they use a vector in a volatile!.
I have not bothered to do any benchmarking, however these are bound to be slower than their clojure.core counterparts, since they are identical but for the addition of some indirection and the use of Clojure collections instead of Java collections. You should not use these unless you need control over the states.
See their usage in noah, which was my motivation for this.
Copyright © 2019 Blake Miller
Distributed under the Eclipse Public License either version 1.0 or (at your option) any later version.