anyone here implemented common CS data structures... (stack, queue...)

[Rob Cozens]

>did anyone here, by chance, implemented common data strucutres like 
>stacks and queues, like  stacks with first in last out behaviour and 
>first in first out behaviour...

Hi Andre,

I have used LIFO queues in HyperTalk and Transcript.

The queues are simply global or declared local variables containing 
lists of transaction requests.  Various handlers check the last line 
of the queue and do different things depending on transaction type.

Example:  OenoLog has a Wine Lot screen where one can add, edit, & 
delete wine lots.  The screen includes a "Thumbs Up" button the user 
clicks to complete a transaction.  When the user initiates a 
transaction, "Add", "Edit", or "Delete" is append to the queue in a 
new trailing line.  On mouseUp the "Thumbs Up" handler checks the 
last line of the queue to determine how to process the data in the 
window.

It can get more complicated:  Suppose I'm in the middle of a Wine Lot 
Edit transaction, and when I'm shown the Grape Variety screen to 
select the correct variety, it isn't listed.  I can interrupt the 
Wine Lot Edit transaction and initiate a Grape Variety Add 
transaction.  The queue now lists "Edit" on one line and "Add" on the 
following line.  The "Thumbs Up" button on the Grape Variety screen 
will process the Add and delete the last line of the queue before 
returning the new Grape Variety to the Wine Lot screen and continuing 
the Edit.

And it can get even more complicated:  Suppose I'm processing a 
Winemaking transaction, and when I get to the source tank selection 
stage I find the tank hasn't been identified to the system.  I must 
interrupt the Winemaking Add transaction and initiated a Tank Add 
transaction. The Tank Add transaction must be interrupted by a Wine 
Lot Add transaction if the Wine Lot in the tank has not been 
identified to the system.  In turn, that transaction can be 
interrupted to initiate Grape Variety Add and Vineyard Add 
transactions is those items are missing.

The use of queue-supported, interruptible transactions allows, among 
other things, the user to immediately begin transaction processing 
with NO initial setup, if desired.

Anything more you'ld like to know.
-- 

Rob Cozens
CCW, Serendipity Software Company

"And I, which was two fooles, do so grow three;
Who are a little wise, the best fooles bee."

from "The Triple Foole" by John Donne (1572-1631)