Here is a sample session running our Scheme interpreter

% ocaml
        Objective Caml version 3.08.3

# #use "main.ml";;
...
Scheme> nil;;
nil evaluates to nil
Scheme> (+ 1 2);;
(+ 1 2) evaluates to 3
Scheme> (+ 1 2 3 4 5);;
(+ 1 2 3 4 5) evaluates to 15
Scheme> (- 3);;
(- 3) evaluates to -3
Scheme> (- 3 4);;
(- 3 4) evaluates to -1
Scheme> (- 3 4 5);;
(- 3 4 5) evaluates to -6
Scheme> (* 1 2 3 4);;
(* 1 2 3 4) evaluates to 24
Scheme> (= 1 2);;
(= 1 2) evaluates to #f
Scheme> (= 1 1);;
(= 1 1) evaluates to #t
Scheme> (boolean? #t);;
(boolean? #t) evaluates to #t
Scheme> (boolean? 3);;
(boolean? 3) evaluates to #f
Scheme> (define three 3);;
(define three 3) evaluates to nil
Scheme> three;;
three evaluates to 3
Scheme> (+ three 4);;
(+ three 4) evaluates to 7
Scheme> (define add-two (lambda (n) (+ n 2)));;
(define add-two (lambda (n) (+ n 2))) evaluates to nil
Scheme> (add-two 5);;
(add-two 5) evaluates to 7
Scheme> (define fact (lambda (n) (if (= n 0) 1 (* n (fact (- n 1))))));;
(define fact (lambda (n) (if (= n 0) 1 (* n (fact (- n 1)))))) evaluates to nil
Scheme> (fact 3);;
(fact 3) evaluates to 6
Scheme> (fact 5);;
(fact 5) evaluates to 120
Scheme> (define x 52);;
(define x 52) evaluates to nil
Scheme> (define foo (lambda (x) (lambda (y) (+ x y))));;
(define foo (lambda (x) (lambda (y) (+ x y)))) evaluates to nil
Scheme> ((foo 3) 4);;
((foo 3) 4) evaluates to 7