Due May 10, 1999 before class

You are given an interpreter for a Scheme-like language written in Scheme. Here is a sample interaction with the interpreter:

/cs/classes/cis624/www/code/exceptions > which scheme
/local/apps/chez-6.0/bin/scheme
/cs/classes/cis624/www/code/exceptions > scheme
Chez Scheme Version 6.0
Copyright (c) 1998 Cadence Research Systems

> (load "interp.ss")
> (rep)
--> (define fact (lambda (n) (if (equal n 0) 1 (* n (fact (sub1 n))))))

--> (fact 5)
120
--> (define x 9)

--> (begin (set! x 5) (fact x))
120
--> (car (cdr (cons 1 (cons 2 (cons 3 (cons 4 emptylist))))))
2
--> quit
> (exit)
/cs/classes/cis624/www/code/exceptions > 

• Implement the missing three clauses in the interpreter that define, raise, and handle exceptions.
• Use your implementation above to raise exceptions if the interpreter attempts to execute (car emptylist) or (cdr emptylist). Your solution should be such that user code can handle this exception.
• Eliminate all other calls to error from interp.ss and env.ss and use exceptions instead. Again user code should be able to handle such exceptions.