Solution to Exercise 2.87

[clean99]

function install_polynomial_package() {
    // ...
  
    function is_termlist_equal_to_zero(termlist) {
        return is_empty_termlist(termlist)
               ? true
               : is_equal_to_zero(coeff(first_term(termlist)))
               ? is_termlist_equal_to_zero(rest_terms(termlist))
               : false;
    }
  
    function is_poly_equal_to_zero(p) {
        return is_termlist_equal_to_zero(term_list(p));
    }
  
    put("is_equal_to_zero", "polynomial",
         is_poly_equal_to_zero);
    //...
}