@Override
 public CompoundInterval visit(
     Variable<CompoundInterval> pVariable,
     Map<? extends String, ? extends InvariantsFormula<CompoundInterval>> pEnvironment) {
   InvariantsFormula<CompoundInterval> varState = pEnvironment.get(pVariable.getName());
   if (varState == null) {
     return CompoundInterval.top();
   }
   return varState.accept(this, pEnvironment);
 }
 @Override
 protected CompoundInterval visitDefault(
     InvariantsFormula<CompoundInterval> pFormula,
     Map<? extends String, ? extends InvariantsFormula<CompoundInterval>> pParam) {
   return abstractionOf(pFormula.accept(EVALUATION_VISITOR, pParam));
 }