DmitrySoshnikov/scheme-on-coffee

Toy Scheme interpreter written in CoffeeScript

# Lisp/Scheme evaluator, see: SICP, 4.1
#
# Port to CoffeeScript
# by Dmitry Soshnikov <dmitry.soshnikov@gmail.com>
# (C) MIT Style License
#

Examples (see http://dmitrysoshnikov.com/coffee-lisp-eval/):

1. Sum:

    Input:

        (+ 1 2 3)

    Output:

        6

2. Define a variable in the Global environment:

    Input:

        (define x 10)

    Output:

        10 ; now x can be referred as bound variable

3. Define a procedure:

    Input:

        (define (sum x y)
                (+ x y))

    Output:

        ok ; procedure object created

4. Eval the sequence (block) of expression:

    Input:

        (begin (define a 10)       ; define "a" variable
               (define b 30)       ; and "b" variable
               (define (square x)
                       (* x x))    ; and a function
               (+ (square a) b))   ; and get the sum of square of "a" and "b"

    Output:

        130

5. Recursion; define the factorial function an call it:

    Input:

        (begin
          (define (factorial n)               ; define the factorial function
              (if (= n 1)
                1
                (* n (factorial (- n 1)))))
          (factorial 5))                      ; and call it for value 5

    Output:

        120

6. Map the list with a lambda expression:

    Input:

        (map (lambda (x) (* x x)) ; anonymous function
              (list 1 2 3 4))      ; maps the list to '(1 4 9 16)

    Output:

        (1 4 9 16)