C311 Assignment 8 -- Dynamic scope

Due Monday, March 27th, at 8:55 AM

Submit via email

1. Define a <static&dynamic-language> class that extends your <let-language> (in which the parser expands let expressions into calls) such that variables whose names begin with a colon are dynamically bound, while all others are statically bound.

   Examples:

   (let ((x 3)
         (y 4))
     (let ((f (lambda (a) (+ a y)))
   	(y 5))
       (f x)))
   
   ==> 7
   
   (let ((x 3)
         (:y 4))
     (let ((f (lambda (a) (+ a :y)))
   	(:y 5))
       (f x)))
   
   ==> 8
   

   The following procedure may be used to determine if a variable name refers to a dynamic variable.

   (define dynamic-var?
     (lambda (var)
       (char=? #\: 
         (string-ref (symbol->string var) 0))))