Re: [Jscheme-user] when do objects get freed

[Timothy J. H. <tim...@ma...>]

On Apr 3, 2004, at 4:19 PM, david wrote:

>
> if I create a java object in a let
>
> (let ((o (java.util.Hashtable.))) ..blah o )
Since "let" is a macro, this gets converted to
  ( (lambda (o p q ..) ...blah  o)
     (java.util.Hashtable.)
     ...
  )
So the o,p,q,... are put into a lexical environment
and bound to their  corresponding values in the "let"
The body is then evaluated (...blah o) and at the end
the lexical symbol "o" is evaluated and its value is
returned. The lexical closure then will be garbage
collected unless it gets captured during the evaluation
of the body and is reachable from non-garbage, eg.

(define f (let ((o (java.util.Hashtable.))
                        (y (java.util.Hashtable.))  )
      (set! g
         (lambda(z)
            (list o y z)))
       o
))

but in normal situations the lexical environment
will be garbage collected ...

(define f (let ((o (java.util.Hashtable.))
                        (y (java.util.Hashtable.))  )
      (.put y 'a 1)
      (.put o 'b y)
       o
))

Does this help??

---Tim---
>
> and return that object so that a reference to it
> is saved , does this prevent other objects
> in the let from being garbage collected?
>
> davud
>
>
>
>
>
>
>
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