// TYPES OF EXPRESSIONS
// 1. Implication
if (opt.equals("<=")){ // type implication
Expression consequence = parseExpression(s.members.get(0));
ExpList premises = parseExpList(s.members.subList(1, s.members.size()));
res = new Implication(consequence, premises);
} else if (opt.equals("=>")){ // type implication
Expression consequence = parseExpression(s.members.get(s.members.size()-1));
ExpList premises = parseExpList(s.members.subList(0, s.members.size()-1));
res = new Implication(consequence, premises);
}
else if (opt.equals("OR") && s.members.size() >= 2)
{
// if (s.members.size() < 2)
// {