[jawsscripts] Re: Resizing arrays
- From: "Travis Roth" <travis@xxxxxxxxxxxxxx>
- To: <jawsscripts@xxxxxxxxxxxxx>
- Date: Thu, 5 Jan 2012 14:20:54 -0600
Yes I thought the array copy was by reference as well.
I have the same problem of not knowing array size in advance.
But it does look useful that you can just make a new array on the existing
variable, I hadn't realized that was possible. Does the old array just stop
existing when new is called again? We've lost access to it but I am just
wondering if JAWS does any garbage collection. I am thinking in the case of
the default scripts, where those global variables are in existence until
JAWS is unloaded, if garbage collection does not automatically occur using
new repeatedly would start to be a memory leak.
Like the ideas... Thanks everyone.
-----Original Message-----
From: jawsscripts-bounce@xxxxxxxxxxxxx
[mailto:jawsscripts-bounce@xxxxxxxxxxxxx] On Behalf Of Doug Lee
Sent: Thursday, January 05, 2012 1:55 PM
To: jawsscripts@xxxxxxxxxxxxx
Subject: [jawsscripts] Re: Resizing arrays
A couple clarifications:
First, to me at least, a "deep copy" is a full duplication of something with
all subparts. My understanding of "s2 = s1" where they are arrays is that,
in JAWS, only the pointer is copied. It still works for your usage though,
so this is mostly just behind-the-scenes stuff for this case.
Second though, your code assumes array sizes, and most of my cases don't
have a clue in advance what size to use. As an example, consider code that
creates a structure of information for each entry in a chat window. If the
process of counting entries is as expensive as that for actually retrieving
them, there's no reasonable way to know in advance how big to make the
array. A collection becomes more efficient in this case, because it is
dynamic while still being amenable to random access.
On Thu, Jan 05, 2012 at 03:59:00PM -0300, Andrew Hart wrote:
I don't understand your need for collections in order to use arrays
globally. You just create the array at the size you need. If you need to
add to it, you just fob it off to a local variable, assign a new larger
array to the global var and then copy the array elements in the local var to
the global one. Then, to finish, you erase the copy of the array by
assigning it an unassigned array var of the same type, much as you would do
with Object vars.
For example:
Var
StringArray s1,
StringArray S2,
StringArray NULLStringArray
s1 = New StringArray[5]
; fill the array with stuff
...
;Copy the array (this is a deep copy, not a shallow copy that only ;passes a
reference pointer)
s2 = s1
s1 = New StringArray[10] ; make the array bigger ; Now copy the contents of
s2 to s1 For i = 1 To 5
s1[i] = s2[i]
EndFor
; erase the array.
; Since JAWS performs deep array copies, it should reduce s2 to its ;minimal
memory footprint, allowing the space to be reclaimed by the ;heap when
appropriate conditions prevail
s2 = NULLStringArray
If you're serious about regularly resizing arrays, I'd recommend making a
few functions using the relevant bits of the above example for resizing
arrays of different types. You'd pass the array being resized by reference
(using ByRef in the function declaration). Also, as this is a linear time
operation, doing it a lot could slow things down if you are dealing with big
arrays. Tricks for dealing with that are to always make the array bigger
than what you need. For example, you could always double the size of the
array whenever you run out of space and then resize it to conserve memory by
removing unused portions later if it is not likely to be added to for a
while.
Hth,
Andrew.
On 5/01/2012 2:32 PM, Travis Roth wrote:
> Perhaps a combination of a collection and an array would work then?
> The documentation states that a collection can hold arrays. So when a
> new array is wanted, delete the old one in the collection and make a new
one.
>
> I am not sure what type of performance that'd give, but might be
> another workaround.
>
> The reason for not just creating new arrays is I need them to be
> global, and there'd be no way to keep track of the names, or at least
> not a practical way.
> Bbut a collection may solve that.
>
> -----Original Message-----
> From: jawsscripts-bounce@xxxxxxxxxxxxx
> [mailto:jawsscripts-bounce@xxxxxxxxxxxxx] On Behalf Of Doug Lee
> Sent: Thursday, January 05, 2012 11:26 AM
> To: jawsscripts@xxxxxxxxxxxxx
> Subject: [jawsscripts] Re: Resizing arrays
>
> JAWS 12 introduced a CollectionRemoveItem function for that.
>
> On Thu, Jan 05, 2012 at 11:23:32AM -0600, Travis Roth wrote:
> Kind of messy but I see your reasoning.
> How do you remove an item from a collection?
>
>
> -----Original Message-----
> From: jawsscripts-bounce@xxxxxxxxxxxxx
> [mailto:jawsscripts-bounce@xxxxxxxxxxxxx] On Behalf Of Doug Lee
> Sent: Thursday, January 05, 2012 10:21 AM
> To: jawsscripts@xxxxxxxxxxxxx
> Subject: [jawsscripts] Re: Resizing arrays
>
> In the absence of knowledge of a way to do that, I've been using
> collections as dynamic arrays, where the keys are things like
> intToString(i). You do need to stringify the keys though. When I do
> that, I also sometimes include a count key that I keep updated when
> adding or removing elements. This also allows for efficient sparse
> arrays but does complicate their management a bit and precludes things
> like inserts/deletes where elements slide in to fill the hole or make
room.
>
> On Thu, Jan 05, 2012 at 10:17:13AM -0600, Travis Roth wrote:
> Is it possible to resize arrays in JAWS script?
> It appears that the arrays are dynamically sized at runtime because
> the new keyword is used.
> But the documentation on the website does not seem to discuss
> destroying or resizing arrays?
> This may not be an issue for local variables, but I am thinking for a
> global array where at some point it may be desireable to store
> something larger than was originally set for.
>
>
>
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