A Changeable is a data structure used to register changes over a certain value
of a given type.
The initial value is supposed to be given on creation, and then subsequent changes
can be registered using addChange.
At any moment the current value (that corresponding to the last active change) can be
accessed using currentValue.
A Changeable is a data structure used to register changes over a certain value of a given type.
The initial value is supposed to be given on creation, and then subsequent changes can be registered using addChange. At any moment the current value (that corresponding to the last active change) can be accessed using currentValue.