Bonus Marks

• › Adapt the builtin function join to work on strings.
• › Adapt the builtin function head to work on strings.
• › Adapt the builtin function tail to work on strings.
• › Create a builtin function read that reads in and converts a string to a Q-expression.
• › Create a builtin function show that can print the contents of strings as it is (unescaped).
• › Create a special value ok to return instead of empty expressions ().
• › Add functions to wrap all of C’s file handling functions such as fopen and fgets.