a doubt about hashCode of Value

[cydonialis]

current implementation of Value's hashCode is:
public int hashCode() { return value; }
but this will result in
Value.makeConstant(0).hashCode() equals Value.getNAC().hashCode() and Value.getUndef().hashCode()

and thus a hashCode of CPFact's instance may not changed when a Value changed.

an optional implementation
public int hashCode() { return toString().hashCode(); }