[jawsscripts] Re: Resizing arrays
- From: Doug Lee <doug.lee@xxxxxxxxxxxxxxxx>
- To: jawsscripts@xxxxxxxxxxxxx
- Date: Thu, 5 Jan 2012 14:55:10 -0500
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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