to clear instance of a variable

as I can recover the previous state of a instanciada variable ?

exists some predicate or method to conduct that operation?

for example:

%in eclipse I define :

X :: 1..4,

%soon instancio X to 3

X is 3,

%then eclipse responds to me that X=3
% some predicate or method exists to recover the variable to its state
X {1..4}
%by its quick answer thanks