Extensii pentru limbajul LET | EOPL3 Let language extensions for list: cons, car, cdr, ...

Constructori:
* listagoala -> ListofExpval
* adauga : expVal x ListofExpval -> ListofExpval

Observatori:
* primul : ListofExpval -> expVal
* restul : ListofExpval -> ListofExpval
* e_goala : ListofExpval -> Bool

> lang.scm___________________________________________________
;;; in the grammar
        (expression
            ("lista-goala")
        gol-exp)

        (expression 
            ("adauga" expression "la" expression)
        add-exp)

        (expression
            ("primul" "din" expression)
        car-exp)

        (expression
            ("restul" "din" expression)
        cdr-exp)

        (expression
            ("e-goala" "(" expression ")")
        isempty-exp)

> interp.scm__________________________________________________
;; in value-of 
        (gol-exp ()
            '()
        )

        (add-exp (exp1 exp2)
            (cons (value-of exp1 env) (value-of exp2 env)))

        (car-exp (exp1)
            (car (value-of exp1 env)))

        (cdr-exp (exp1)
            (cdr (value-of exp1 env)))

        (isempty-exp (exp1)
            (bool-val (null? (value-of exp1 env))))

> tests.scm____________________________________________________
        (lista-test1 "adauga 5 la adauga 6 la lista-goala" (5 6))
        (lista-test2 "lista-goala" ())
        (lista-test3 "let x=1 in adauga x la lista-goala" (1))
        (lista-test4 "adauga zero?(1) la adauga 5 la adauga let x = 2 in -(x,1) la lista-goala" (#f 5 1))
        (lista-test5 "e-goala(lista-goala)" #t)
        (lista-test6 "e-goala(adauga 3 la lista-goala)" #f)
        (lista-test7 "primul din let x=1 in adauga x la lista-goala" 1)
        (lista-test8 "restul din adauga zero?(1) la adauga 5 la adauga let x = 2 in -(x,1) la lista-goala" (5 1))

> top.scm______________________________________________________
;;; in sloppy->expval  (for tests.scm)
((list? sloppy-val) (map sloppy->expval sloppy-val))