Rework empty list as a literal.

Author: dvanhorn

langs/hustle/interp-heap-bits.rkt

@@ -20,7 +20,6 @@
   (match e    
     [(Lit d)  (cons h (value->bits d))]
     [(Eof)    (cons h (value->bits eof))]
-    [(Empty)  (cons h (value->bits '()))]
     [(Var x)  (cons h (lookup r x))]
     [(Prim0 'void) (cons h (value->bits (void)))]
     [(Prim0 'read-byte) (cons h (value->bits (read-byte)))]

langs/hustle/interp-heap.rkt

@@ -30,7 +30,6 @@
 (define (interp-env-heap e r h)
   (match e
     [(Lit d)  (cons h d)]
-    [(Empty)  (cons h '())]
     [(Eof)    (cons h eof)]
     [(Var x)  (cons h (lookup r x))]
     [(Prim0 'void) (cons h (void))]