A Mutator is an abstract data type declaration of the form:

interface Mutator<Action : Any, State : Any> {
    val state: State
    val accept: (Action) -> Unit
}

where Action defines an input type that yields production of the State output type. In other words, a Mutator represents a production pipeline of State which may be altered by input of Action.

The unit of change for processing an Action into a new State is a Mutation, a data class hosting a lambda with the existing State as a receiver, that when invoked produces a new State.

data class Mutation<T : Any>(
    val mutate: T.() -> T
)

The default implementation is the stateFlowMutator.

A sample app utilizing it (and coincidentally what this post was written with) can be found here: