;    Initialization file for TinySCHEME 1.41

; Per R5RS, up to four deep compositions should be defined
(define (caar x) (car (car x)))
(define (cadr x) (car (cdr x)))
(define (cdar x) (cdr (car x)))
(define (cddr x) (cdr (cdr x)))
(define (caaar x) (car (car (car x))))
(define (caadr x) (car (car (cdr x))))
(define (cadar x) (car (cdr (car x))))
(define (caddr x) (car (cdr (cdr x))))
(define (cdaar x) (cdr (car (car x))))
(define (cdadr x) (cdr (car (cdr x))))
(define (cddar x) (cdr (cdr (car x))))
(define (cdddr x) (cdr (cdr (cdr x))))
(define (caaaar x) (car (car (car (car x)))))
(define (caaadr x) (car (car (car (cdr x)))))
(define (caadar x) (car (car (cdr (car x)))))
(define (caaddr x) (car (car (cdr (cdr x)))))
(define (cadaar x) (car (cdr (car (car x)))))
(define (cadadr x) (car (cdr (car (cdr x)))))
(define (caddar x) (car (cdr (cdr (car x)))))
(define (cadddr x) (car (cdr (cdr (cdr x)))))
(define (cdaaar x) (cdr (car (car (car x)))))
(define (cdaadr x) (cdr (car (car (cdr x)))))
(define (cdadar x) (cdr (car (cdr (car x)))))
(define (cdaddr x) (cdr (car (cdr (cdr x)))))
(define (cddaar x) (cdr (cdr (car (car x)))))
(define (cddadr x) (cdr (cdr (car (cdr x)))))
(define (cdddar x) (cdr (cdr (cdr (car x)))))
(define (cddddr x) (cdr (cdr (cdr (cdr x)))))

;;;; Utility to ease macro creation
(define (macro-expand form)
     ((eval (get-closure-code (eval (car form)))) form))

(define (macro-expand-all form)
   (if (macro? form)
      (macro-expand-all (macro-expand form))
      form))

(define *compile-hook* macro-expand-all)


(macro (unless form)
     `(if (not ,(cadr form)) (begin ,@(cddr form))))

(macro (when form)
     `(if ,(cadr form) (begin ,@(cddr form))))

; DEFINE-MACRO Contributed by Andy Gaynor
(macro (define-macro dform)
  (if (symbol? (cadr dform))
    `(macro ,@(cdr dform))
    (let ((form (gensym)))
      `(macro (,(caadr dform) ,form)
         (apply (lambda ,(cdadr dform) ,@(cddr dform)) (cdr ,form))))))

; Utilities for math. Notice that inexact->exact is primitive,
; but exact->inexact is not.
(define exact? integer?)
(define (inexact? x) (and (real? x) (not (integer? x))))
(define (even? n) (= (remainder n 2) 0))
(define (odd? n) (not (= (remainder n 2) 0)))
(define (zero? n) (= n 0))
(define (positive? n) (> n 0))
(define (negative? n) (< n 0))
(define complex? number?)
(define rational? real?)
(define (abs n) (if (>= n 0) n (- n)))
(define (exact->inexact n) (* n 1.0))
(define (<> n1 n2) (not (= n1 n2)))

; min and max must return inexact if any arg is inexact; use (+ n 0.0)
(define (max . lst)
  (foldr (lambda (a b)
           (if (> a b)
             (if (exact? b) a (+ a 0.0))
             (if (exact? a) b (+ b 0.0))))
         (car lst) (cdr lst)))
(define (min . lst)
  (foldr (lambda (a b)
           (if (< a b)
             (if (exact? b) a (+ a 0.0))
             (if (exact? a) b (+ b 0.0))))
         (car lst) (cdr lst)))

(define (succ x) (+ x 1))
(define (pred x) (- x 1))
(define gcd
  (lambda a
    (if (null? a)
      0
      (let ((aa (abs (car a)))
            (bb (abs (cadr a))))
         (if (= bb 0)
              aa
              (gcd bb (remainder aa bb)))))))
(define lcm
  (lambda a
    (if (null? a)
      1
      (let ((aa (abs (car a)))
            (bb (abs (cadr a))))
         (if (or (= aa 0) (= bb 0))
             0
             (abs (* (quotient aa (gcd aa bb)) bb)))))))


(define (string . charlist)
     (list->string charlist))

(define (list->string charlist)
     (let* ((len (length charlist))
            (newstr (make-string len))
            (fill-string!
               (lambda (str i len charlist)
                    (if (= i len)
                         str
                         (begin (string-set! str i (car charlist))
                         (fill-string! str (+ i 1) len (cdr charlist)))))))
          (fill-string! newstr 0 len charlist)))

(define (string-fill! s e)
     (let ((n (string-length s)))
          (let loop ((i 0))
               (if (= i n)
                    s
                    (begin (string-set! s i e) (loop (succ i)))))))

(define (string->list s)
     (let loop ((n (pred (string-length s))) (l '()))
          (if (= n -1)
               l
               (loop (pred n) (cons (string-ref s n) l)))))

(define (string-copy str)
     (string-append str))

(define (string->anyatom str pred)
     (let* ((a (string->atom str)))
       (if (pred a) a
         (error "string->xxx: not a xxx" a))))

(define (string->number str . base)
    (let ((n (string->atom str (if (null? base) 10 (car base)))))
        (if (number? n) n #f)))

(define (anyatom->string n pred)
  (if (pred n)
      (atom->string n)
      (error "xxx->string: not a xxx" n)))

(define (number->string n . base)
    (atom->string n (if (null? base) 10 (car base))))


(define (char-cmp? cmp a b)
     (cmp (char->integer a) (char->integer b)))
(define (char-ci-cmp? cmp a b)
     (cmp (char->integer (char-downcase a)) (char->integer (char-downcase b))))

(define (char=? a b) (char-cmp? = a b))
(define (char<? a b) (char-cmp? < a b))
(define (char>? a b) (char-cmp? > a b))
(define (char<=? a b) (char-cmp? <= a b))
(define (char>=? a b) (char-cmp? >= a b))

(define (char-ci=? a b) (char-ci-cmp? = a b))
(define (char-ci<? a b) (char-ci-cmp? < a b))
(define (char-ci>? a b) (char-ci-cmp? > a b))
(define (char-ci<=? a b) (char-ci-cmp? <= a b))
(define (char-ci>=? a b) (char-ci-cmp? >= a b))

; Note the trick of returning (cmp x y)
(define (string-cmp? chcmp cmp a b)
     (let ((na (string-length a)) (nb (string-length b)))
          (let loop ((i 0))
               (cond
                    ((= i na)
                         (if (= i nb) (cmp 0 0) (cmp 0 1)))
                    ((= i nb)
                         (cmp 1 0))
                    ((chcmp = (string-ref a i) (string-ref b i))
                         (loop (succ i)))
                    (else
                         (chcmp cmp (string-ref a i) (string-ref b i)))))))


(define (string=? a b) (string-cmp? char-cmp? = a b))
(define (string<? a b) (string-cmp? char-cmp? < a b))
(define (string>? a b) (string-cmp? char-cmp? > a b))
(define (string<=? a b) (string-cmp? char-cmp? <= a b))
(define (string>=? a b) (string-cmp? char-cmp? >= a b))

(define (string-ci=? a b) (string-cmp? char-ci-cmp? = a b))
(define (string-ci<? a b) (string-cmp? char-ci-cmp? < a b))
(define (string-ci>? a b) (string-cmp? char-ci-cmp? > a b))
(define (string-ci<=? a b) (string-cmp? char-ci-cmp? <= a b))
(define (string-ci>=? a b) (string-cmp? char-ci-cmp? >= a b))

(define (list . x) x)

(define (foldr f x lst)
     (if (null? lst)
          x
          (foldr f (f x (car lst)) (cdr lst))))

(define (unzip1-with-cdr . lists)
  (unzip1-with-cdr-iterative lists '() '()))

(define (unzip1-with-cdr-iterative lists cars cdrs)
  (if (null? lists)
      (cons cars cdrs)
      (let ((car1 (caar lists))
            (cdr1 (cdar lists)))
        (unzip1-with-cdr-iterative
          (cdr lists)
          (append cars (list car1))
          (append cdrs (list cdr1))))))

(define (map proc . lists)
  (if (null? lists)
      (apply proc)
      (if (null? (car lists))
        '()
        (let* ((unz (apply unzip1-with-cdr lists))
               (cars (car unz))
               (cdrs (cdr unz)))
          (cons (apply proc cars) (apply map (cons proc cdrs)))))))

(define (for-each proc . lists)
  (if (null? lists)
      (apply proc)
      (if (null? (car lists))
        #t
        (let* ((unz (apply unzip1-with-cdr lists))
               (cars (car unz))
               (cdrs (cdr unz)))
          (apply proc cars) (apply map (cons proc cdrs))))))

(define (list-tail x k)
    (if (zero? k)
        x
        (list-tail (cdr x) (- k 1))))

(define (list-ref x k)
    (car (list-tail x k)))

(define (last-pair x)
    (if (pair? (cdr x))
        (last-pair (cdr x))
        x))

(define (head stream) (car stream))

(define (tail stream) (force (cdr stream)))

(define (vector-equal? x y)
     (and (vector? x) (vector? y) (= (vector-length x) (vector-length y))
          (let ((n (vector-length x)))
               (let loop ((i 0))
                    (if (= i n)
                         #t
                         (and (equal? (vector-ref x i) (vector-ref y i))
                              (loop (succ i))))))))

(define (list->vector x)
     (apply vector x))

(define (vector-fill! v e)
     (let ((n (vector-length v)))
          (let loop ((i 0))
               (if (= i n)
                    v
                    (begin (vector-set! v i e) (loop (succ i)))))))

(define (vector->list v)
     (let loop ((n (pred (vector-length v))) (l '()))
          (if (= n -1)
               l
               (loop (pred n) (cons (vector-ref v n) l)))))

;; The following quasiquote macro is due to Eric S. Tiedemann.
;;   Copyright 1988 by Eric S. Tiedemann; all rights reserved.
;;
;; Subsequently modified to handle vectors: D. Souflis

(macro
 quasiquote
 (lambda (l)
   (define (mcons f l r)
     (if (and (pair? r)
              (eq? (car r) 'quote)
              (eq? (car (cdr r)) (cdr f))
              (pair? l)
              (eq? (car l) 'quote)
              (eq? (car (cdr l)) (car f)))
         (if (or (procedure? f) (number? f) (string? f))
               f
               (list 'quote f))
         (if (eqv? l vector)
               (apply l (eval r))
               (list 'cons l r)
               )))
   (define (mappend f l r)
     (if (or (null? (cdr f))
             (and (pair? r)
                  (eq? (car r) 'quote)
                  (eq? (car (cdr r)) '())))
         l
         (list 'append l r)))
   (define (foo level form)
     (cond ((not (pair? form))
               (if (or (procedure? form) (number? form) (string? form))
                    form
                    (list 'quote form))
               )
           ((eq? 'quasiquote (car form))
            (mcons form ''quasiquote (foo (+ level 1) (cdr form))))
           (#t (if (zero? level)
                   (cond ((eq? (car form) 'unquote) (car (cdr form)))
                         ((eq? (car form) 'unquote-splicing)
                          (error "Unquote-splicing wasn't in a list:"
                                 form))
                         ((and (pair? (car form))
                               (eq? (car (car form)) 'unquote-splicing))
                          (mappend form (car (cdr (car form)))
                                   (foo level (cdr form))))
                         (#t (mcons form (foo level (car form))
                                         (foo level (cdr form)))))
                   (cond ((eq? (car form) 'unquote)
                          (mcons form ''unquote (foo (- level 1)
                                                     (cdr form))))
                         ((eq? (car form) 'unquote-splicing)
                          (mcons form ''unquote-splicing
                                      (foo (- level 1) (cdr form))))
                         (#t (mcons form (foo level (car form))
                                         (foo level (cdr form)))))))))
   (foo 0 (car (cdr l)))))

;;;;;Helper for the dynamic-wind definition.  By Tom Breton (Tehom)
(define (shared-tail x y)
   (let ((len-x (length x))
         (len-y (length y)))
      (define (shared-tail-helper x y)
         (if
            (eq? x y)
            x
            (shared-tail-helper (cdr x) (cdr y))))

      (cond
         ((> len-x len-y)
            (shared-tail-helper
               (list-tail x (- len-x len-y))
               y))
         ((< len-x len-y)
            (shared-tail-helper
               x
               (list-tail y (- len-y len-x))))
         (#t (shared-tail-helper x y)))))

;;;;;Dynamic-wind by Tom Breton (Tehom)

;;Guarded because we must only eval this once, because doing so
;;redefines call/cc in terms of old call/cc
(unless (defined? 'dynamic-wind)
   (let
      ;;These functions are defined in the context of a private list of
      ;;pairs of before/after procs.
      (  (*active-windings* '())
         ;;We'll define some functions into the larger environment, so
         ;;we need to know it.
         (outer-env (current-environment)))

      ;;Poor-man's structure operations
      (define before-func car)
      (define after-func  cdr)
      (define make-winding cons)

      ;;Manage active windings
      (define (activate-winding! new)
         ((before-func new))
         (set! *active-windings* (cons new *active-windings*)))
      (define (deactivate-top-winding!)
         (let ((old-top (car *active-windings*)))
            ;;Remove it from the list first so it's not active during its
            ;;own exit.
            (set! *active-windings* (cdr *active-windings*))
            ((after-func old-top))))

      (define (set-active-windings! new-ws)
         (unless (eq? new-ws *active-windings*)
            (let ((shared (shared-tail new-ws *active-windings*)))

               ;;Define the looping functions.
               ;;Exit the old list.  Do deeper ones last.  Don't do
               ;;any shared ones.
               (define (pop-many)
                  (unless (eq? *active-windings* shared)
                     (deactivate-top-winding!)
                     (pop-many)))
               ;;Enter the new list.  Do deeper ones first so that the
               ;;deeper windings will already be active.  Don't do any
               ;;shared ones.
               (define (push-many new-ws)
                  (unless (eq? new-ws shared)
                     (push-many (cdr new-ws))
                     (activate-winding! (car new-ws))))

               ;;Do it.
               (pop-many)
               (push-many new-ws))))

      ;;The definitions themselves.
      (eval
         `(define call-with-current-continuation
             ;;It internally uses the built-in call/cc, so capture it.
             ,(let ((old-c/cc call-with-current-continuation))
                 (lambda (func)
                    ;;Use old call/cc to get the continuation.
                    (old-c/cc
                       (lambda (continuation)
                          ;;Call func with not the continuation itself
                          ;;but a procedure that adjusts the active
                          ;;windings to what they were when we made
                          ;;this, and only then calls the
                          ;;continuation.
                          (func
                             (let ((current-ws *active-windings*))
                                (lambda (x)
                                   (set-active-windings! current-ws)
                                   (continuation x)))))))))
         outer-env)
      ;;We can't just say "define (dynamic-wind before thunk after)"
      ;;because the lambda it's defined to lives in this environment,
      ;;not in the global environment.
      (eval
         `(define dynamic-wind
             ,(lambda (before thunk after)
                 ;;Make a new winding
                 (activate-winding! (make-winding before after))
                 (let ((result (thunk)))
                    ;;Get rid of the new winding.
                    (deactivate-top-winding!)
                    ;;The return value is that of thunk.
                    result)))
         outer-env)))

(define call/cc call-with-current-continuation)


;;;;; atom? and equal? written by a.k

;;;; atom?
(define (atom? x)
  (not (pair? x)))

;;;;    equal?
(define (equal? x y)
     (cond
          ((pair? x)
               (and (pair? y)
                    (equal? (car x) (car y))
                    (equal? (cdr x) (cdr y))))
          ((vector? x)
               (and (vector? y) (vector-equal? x y)))
          ((string? x)
               (and (string? y) (string=? x y)))
          (else (eqv? x y))))

;;;; (do ((var init inc) ...) (endtest result ...) body ...)
;;
(macro do
  (lambda (do-macro)
    (apply (lambda (do vars endtest . body)
             (let ((do-loop (gensym)))
               `(letrec ((,do-loop
                           (lambda ,(map (lambda (x)
                                           (if (pair? x) (car x) x))
                                      `,vars)
                             (if ,(car endtest)
                               (begin ,@(cdr endtest))
                               (begin
                                 ,@body
                                 (,do-loop
                                   ,@(map (lambda (x)
                                            (cond
                                              ((not (pair? x)) x)
                                              ((< (length x) 3) (car x))
                                              (else (car (cdr (cdr x))))))
                                       `,vars)))))))
                  (,do-loop
                    ,@(map (lambda (x)
                             (if (and (pair? x) (cdr x))
                               (car (cdr x))
                               '()))
                        `,vars)))))
      do-macro)))

;;;; generic-member
(define (generic-member cmp obj lst)
  (cond
    ((null? lst) #f)
    ((cmp obj (car lst)) lst)
    (else (generic-member cmp obj (cdr lst)))))

(define (memq obj lst)
     (generic-member eq? obj lst))
(define (memv obj lst)
     (generic-member eqv? obj lst))
(define (member obj lst)
     (generic-member equal? obj lst))

;;;; generic-assoc
(define (generic-assoc cmp obj alst)
     (cond
          ((null? alst) #f)
          ((cmp obj (caar alst)) (car alst))
          (else (generic-assoc cmp obj (cdr alst)))))

(define (assq obj alst)
     (generic-assoc eq? obj alst))
(define (assv obj alst)
     (generic-assoc eqv? obj alst))
(define (assoc obj alst)
     (generic-assoc equal? obj alst))

(define (acons x y z) (cons (cons x y) z))

;;;; Handy for imperative programs
;;;; Used as: (define-with-return (foo x y) .... (return z) ...)
(macro (define-with-return form)
     `(define ,(cadr form)
          (call/cc (lambda (return) ,@(cddr form)))))

;; Print the given history.
(define (vm-history-print history)
  (let loop ((n 0) (skip 0) (frames history))
    (cond
     ((null? frames)
      #t)
     ((> skip 0)
      (loop 0 (- skip 1) (cdr frames)))
     (else
      (let ((f (car frames)))
	(display n)
	(display ": ")
	(let ((tag (get-tag f)))
	  (when (and (pair? tag) (string? (car tag)) (number? (cdr tag)))
		(display (basename (car tag)))
		(display ":")
		(display (+ 1 (cdr tag)))
		(display ": ")))
	(write f))
	(newline)
	(loop (+ n 1) skip (cdr frames))))))

;;;; Simple exception handling
;
;    Exceptions are caught as follows:
;
;         (catch (do-something to-recover and-return meaningful-value)
;              (if-something goes-wrong)
;              (with-these calls))
;
;    "Catch" establishes a scope spanning multiple call-frames until
;    another "catch" is encountered.  Within the recovery expression
;    the thrown exception is bound to *error*.  Errors can be rethrown
;    using (rethrow *error*).
;
;    Finalization can be expressed using "finally":
;
;         (finally (finalize-something called-purely-for side-effects)
;              (whether-or-not something goes-wrong)
;              (with-these calls))
;
;    The final expression is executed purely for its side-effects,
;    both when the function exits successfully, and when an exception
;    is thrown.
;
;    Exceptions are thrown with:
;
;         (throw "message")
;
;    If used outside a (catch ...), reverts to (error "message")

(define *handlers* (list))

(define (push-handler proc)
     (set! *handlers* (cons proc *handlers*)))

(define (pop-handler)
     (let ((h (car *handlers*)))
          (set! *handlers* (cdr *handlers*))
          h))

(define (more-handlers?)
     (pair? *handlers*))

;; This throws an exception.
(define (throw message . args)
  (throw' message args (cdr (*vm-history*))))

;; This is used by the vm to throw exceptions.
(define (throw' message args history)
  (cond
   ((and args (list? args) (= 2 (length args))
	 (equal? *interpreter-exit* (car args)))
    (*run-atexit-handlers*)
    (quit (cadr args)))
   ((more-handlers?)
    ((pop-handler) message args history))
   (else
    (display message)
    (when (and args (not (null? args)))
	  (display ": ")
	  (if (and (pair? args) (string? (car args)))
	      (begin (display (car args))
		     (unless (null? (cdr args))
			     (newline)
			     (write (cdr args))))
	      (write args)))
    (newline)
    (vm-history-print history)
    (quit 1))))

;; Convenience function to rethrow the error.
(define (rethrow e)
  (apply throw' e))

(macro (catch form)
     (let ((label (gensym)))
          `(call/cc (lambda (**exit**)
               (push-handler (lambda *error* (**exit** ,(cadr form))))
               (let ((,label (begin ,@(cddr form))))
                    (pop-handler)
                    ,label)))))

(define-macro (finally final-expression . expressions)
  (let ((result (gensym)))
    `(let ((,result (catch (begin ,final-expression (rethrow *error*))
			   ,@expressions)))
       ,final-expression
       ,result)))

;; Make the vm use throw'.
(define *error-hook* throw')



;; High-level mechanism to terminate the process is to throw an error
;; of the form (*interpreter-exit* status).  This gives automatic
;; resource management a chance to clean up.
(define *interpreter-exit* (gensym))

;; Terminate the process returning STATUS to the parent.
(define (exit status)
  (throw "interpreter exit" *interpreter-exit* status))

;; A list of functions run at interpreter shutdown.
(define *atexit-handlers* (list))

;; Execute all these functions.
(define (*run-atexit-handlers*)
  (unless (null? *atexit-handlers*)
	  (let ((proc (car *atexit-handlers*)))
	    ;; Drop proc from the list so that it will not get
	    ;; executed again even if it raises an exception.
	    (set! *atexit-handlers* (cdr *atexit-handlers*))
	    (proc)
	    (*run-atexit-handlers*))))

;; Register a function to be run at interpreter shutdown.
(define (atexit proc)
  (set! *atexit-handlers* (cons proc *atexit-handlers*)))



;;;;; Definition of MAKE-ENVIRONMENT, to be used with two-argument EVAL

(macro (make-environment form)
     `(apply (lambda ()
               ,@(cdr form)
               (current-environment))))

(define-macro (eval-polymorphic x . envl)
  (display envl)
  (let* ((env (if (null? envl) (current-environment) (eval (car envl))))
         (xval (eval x env)))
    (if (closure? xval)
      (make-closure (get-closure-code xval) env)
      xval)))

; Redefine this if you install another package infrastructure
; Also redefine 'package'
(define *colon-hook* eval)

(macro (package form)
  `(apply (lambda ()
	    ,@(cdr form)
	    (current-environment))))

(define-macro (export name . expressions)
  `(define ,name
     (begin
       ,@expressions)))

;;;;; I/O

(define (input-output-port? p)
     (and (input-port? p) (output-port? p)))

(define (close-port p)
     (cond
          ((input-output-port? p) (close-input-port p) (close-output-port p))
          ((input-port? p) (close-input-port p))
          ((output-port? p) (close-output-port p))
          (else (throw "Not a port" p))))

(define (call-with-input-file s p)
     (let ((inport (open-input-file s)))
          (if (eq? inport #f)
               #f
               (let ((res (p inport)))
                    (close-input-port inport)
                    res))))

(define (call-with-output-file s p)
     (let ((outport (open-output-file s)))
          (if (eq? outport #f)
               #f
               (let ((res (p outport)))
                    (close-output-port outport)
                    res))))

(define (with-input-from-file s p)
     (let ((inport (open-input-file s)))
          (if (eq? inport #f)
               #f
               (let ((prev-inport (current-input-port)))
                    (set-input-port inport)
                    (let ((res (p)))
                         (close-input-port inport)
                         (set-input-port prev-inport)
                         res)))))

(define (with-output-to-file s p)
     (let ((outport (open-output-file s)))
          (if (eq? outport #f)
               #f
               (let ((prev-outport (current-output-port)))
                    (set-output-port outport)
                    (let ((res (p)))
                         (close-output-port outport)
                         (set-output-port prev-outport)
                         res)))))

(define (with-input-output-from-to-files si so p)
     (let ((inport (open-input-file si))
           (outport (open-input-file so)))
          (if (not (and inport outport))
               (begin
                    (close-input-port inport)
                    (close-output-port outport)
                    #f)
               (let ((prev-inport (current-input-port))
                     (prev-outport (current-output-port)))
                    (set-input-port inport)
                    (set-output-port outport)
                    (let ((res (p)))
                         (close-input-port inport)
                         (close-output-port outport)
                         (set-input-port prev-inport)
                         (set-output-port prev-outport)
                         res)))))

; Random number generator (maximum cycle)
(define *seed* 1)
(define (random-next)
     (let* ((a 16807) (m 2147483647) (q (quotient m a)) (r (modulo m a)))
          (set! *seed*
               (-   (* a (- *seed*
                         (* (quotient *seed* q) q)))
                    (* (quotient *seed* q) r)))
          (if (< *seed* 0) (set! *seed* (+ *seed* m)))
          *seed*))
;; SRFI-0
;; COND-EXPAND
;; Implemented as a macro
(define *features* '(srfi-0 tinyscheme))

(define-macro (cond-expand . cond-action-list)
  (cond-expand-runtime cond-action-list))

(define (cond-expand-runtime cond-action-list)
  (if (null? cond-action-list)
      #t
      (if (cond-eval (caar cond-action-list))
          `(begin ,@(cdar cond-action-list))
          (cond-expand-runtime (cdr cond-action-list)))))

(define (cond-eval-and cond-list)
  (foldr (lambda (x y) (and (cond-eval x) (cond-eval y))) #t cond-list))

(define (cond-eval-or cond-list)
  (foldr (lambda (x y) (or (cond-eval x) (cond-eval y))) #f cond-list))

(define (cond-eval condition)
  (cond
    ((symbol? condition)
       (if (member condition *features*) #t #f))
    ((eq? condition #t) #t)
    ((eq? condition #f) #f)
    (else (case (car condition)
            ((and) (cond-eval-and (cdr condition)))
            ((or) (cond-eval-or (cdr condition)))
            ((not) (if (not (null? (cddr condition)))
                     (error "cond-expand : 'not' takes 1 argument")
                     (not (cond-eval (cadr condition)))))
            (else (error "cond-expand : unknown operator" (car condition)))))))

(gc-verbose #f)
