
;;; Cedar Scheme Derived Expressions

;;; Binding Forms
;;; Conditionals

(extend-syntax (when)
(  (when predicate body more ...)
(if predicate (begin body more ...))))

(extend-syntax (unless)
(  (unless predicate body more ...)
(if (not predicate) (begin body more ...))))

;;; Syntax Extension

(extend-syntax (macro)
(  (macro name proc)
(with ((var (gensym)))
(define name
(make-syntax
(lambda var
(proc (cons 'name var))))))))

;;; Simple Modularity

(extend-syntax (export)
((export (var ...) defn ...)
(begin
(define var #f) ...
(let ((lst (let () defn ... (list var ...))))
 { (set! var (car lst))
(set! lst (cdr lst))} ...)
'(var ...))))


   ˆ  
;;; Syntax2.scheme
;;; Copyright Ó 1988, 1989, 1991 by Xerox Corporation.  All rights reserved.
;;; Last changed by Pavel on August 11, 1989 4:18:39 pm PDT
;;; Michael Plass, January 21, 1989 0:05:43 am PST

;; Obsolete:
(extend-syntax (fluid-let)
(  (fluid-let ((var val) ...)
   body
more-body ...)
(with (((saved-var ...) (map (lambda (x) (gensym)) '(var ...)))
    (swap! (gensym))
    (temp (gensym)))
(let ((saved-var val) ... (temp #f))
(let ((swap! (lambda ()
             { (set! temp var)
            (set! var saved-var)
         (set! saved-var temp)
    } ...)))
(dynamic-wind
swap!
(lambda () body more-body ...)
swap!))))))

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