/** * \file eval.hpp * * Encapsulates the interface for the expression evaluator function. */#ifndef EVAL_HPP#define EVAL_HPP#include "cons.hpp"using namespace std;/** * \brief Evaluate the expression tree whose root is pointed to by c * (error if c does not hold a well-formed expression). * * \return The value resulting from evaluating the expression. */Cell* eval(Cell* const c);#endif // EVAL_HPP