;; mole - vectored forth vm

;; main ideas:
;; - primitives are C functions -> interpreter is a trampoline / loop
;; - forth return stack is a separate (abstract: list,vector,?) structure
;; - proper tail calls
;; - words are tagged: at least 2 bits are used: literal + exit.

(require "cgen.ss")


(extend-expressions
 (transformer

  (define (car x) `(index ,x 0))
  (define (cdr x) `(index ,x 1))

  ;; stacks are easier on the eye as lvalues
  (define (top stack)  `(* ,stack))
  (define (push stack) `(* (pre  ++ ,stack)))
  (define (pop stack)  `(* (post -- ,stack)))))


(define-syntax mole
  (syntax-rules ()
    ((_ statement ...)
     (display
      (statement->string
       '(statements statement ...))))))


(mole
  (= (push s) 123)
  (= a (pop s))
  (= b (top s)))