Re: [Jscheme-devel] Re: JScheme SchemeApplet - UC WISE Citris Project

[Dazhi L. <da...@uc...>]

Thank you very much! I'll integrate this into the listener.

Regards,
Darrel

Timothy Hickey wrote:

>
> On Sunday, May 26, 2002, at 02:15 PM, Dazhi Liu wrote:
>
>> BTW, a quick question: After user program in JScheme for a while, is
>> there an easy way to erase all user defined bindings, that is, to return
>> to the initial state of JScheme?
>>
>
>
>
> Its not too hard. At the end of this note is a procedure that creates
> a SymbolTable
> restorer. You use it as
>
> > (define z (make-state-restorer))
> ....
> > (z)
> and it will restore your state to the initial one.
>
>
>
> ;; This is a System restorer
> ;; It makes a copy of the Symbol table state which it stores in its
> returned value
> ;; > (define z (make-state-restorer))
> ;; When you later invoke the thunk
> ;; > (z)
> ;; it resets the Symbol table to its
> ;; original values (but it doesn't reset the javadot primitives as
> this would just
> ;; waste time).
>
> (define (make-state-restorer)
> (let
> ((ST0
> (java.util.Hashtable.))
> (isJavadot (lambda (x)
> (or (> (.indexOf x ".") -1) (> (.indexOf x "$") -1))))
> (enum->list
> (lambda(E)
> (let loop ((L ()))
> (if (.hasMoreElements E)
> (loop (cons (.nextElement E) L))
> L)))))
> (for-each
> (lambda(x)
> (if (not (isJavadot x)) ;; don't remember javadots!
> (.put ST0 x
> (tryCatch
> (list (.getGlobalValue (string->symbol x)))
> (lambda(e)
> ())))))
> (enum->list (.keys jsint.Symbol.symbolTable$)))
>
> (display (length (enum->list (.keys ST0))))(newline)
>
> (lambda()
> (let ((ST jsint.Symbol.symbolTable$))
> (for-each
> (lambda(x)
> (let ((v (.get ST0 x)))
> (if (equal? #null v)
> (if (not (isJavadot x))
> (begin (display x)(newline) (.remove ST x)))
> (let ((s (string->symbol x)))
> (.put ST x s)
> (if (not (null? v))
> (.setGlobalValue s (first v)))))))
> (enum->list (.keys ST)))))))
>
>
>