@Override
protected void visit(RENode.CharacterClassExpr.Char expr) throws RuntimeException {
solver = new Solver.Char(expr.getValue());
}
@Override
protected void visit(RENode.CharacterClassExpr.Range expr) throws RuntimeException {
RENode.CharacterClassExpr.Char from = expr.getFrom();
RENode.CharacterClassExpr.Char to = expr.getTo();
solver = new Solver.Range(from.getValue(), to.getValue());
}