A new variable scope

[G Gabriel]

To borrow the words of Robert Kennedy:
"Some people look at things and say why; I see things that never were and say why not!"

Variables are accessible within their scope and when you get out of alpha, they all die. That goes for any variable in just about any software programming.

So to suggest that you could make a variable survive after you get out of your program would sound like blasphemy to programming geeks and is bound to send you to the gallows.

Not that I have a death wish, but what prompted this idea is couple of recent threads.

So the question is: can you somehow retool or genetically engineer a variable to make it survive after you exist alpha?

The answer is yes.

Not only it will survive after you exit alpha, it will do so if you exit Windows, if you turn off the power to your machine, to the whole building or the entire neighborhood.
How?
As Jack Palace would say: "that's for you to figure out."

Thought you might be interested in a little brainteaser..Will post the response shortly.

[michaelwpayton]

Re: A new variable scope

"application cookies," there're not just for Web servers/apps... we have been saving/restoring an application's "state," by "user/session" for 20+ years...

[aschone]

Re: A new variable scope

Text file in application directory. Update the text file with your variable and their values.

[Marcel Kollenaar]

Re: A new variable scope

There a more ways to do that, property file, ini file, etc.

'Adapted from the help file
'Create a dot variable
Dim a[1] as P
a[1].name = "Fred"
a[1].city = "Boston"
a[1].age = 23
a[].name = "Tom"
a[..].city = "NY"
a[..].age = 35
 
'Show how the properties looks like
ui_msg_box("Write properties to file",properties_enum(a[1],"R;O=p|v|t"))
 
'Write 'm to disk
file.From_property("c:\my_property.txt", a)
 
'Delete the pointer var
delete a
 
dim b as P
dim a[1] as P
dim cc as C
 
'Read the properties from the property file
cc = file.to_property("c:\my_property.txt", b)
 
'Show the property string
ui_msg_box("Read property string from propertyfile",cc)
 
'Convert them from propety string into a property var
property_from_string(a, cc)
 
'Show the property var
ui_msg_box("Enum properties",properties_enum(a[1],"R;O=p|v|t"))

[csda1]

Re: A new variable scope

This has been covered multiple times on the board, but variable scope basically comes down to this

• Local variables - persistent within the current function or script
• Shared/Session variables - persistent through the current session (thread), typically a window in Alpha 5
• Global variables - persistent until the database closes
• Addin variables - persistent until the Alpha 5 window closes, even closing and opening other databases

Any other variable value that you want persistent values to is just a matter of storing it in an ADB file, database, registry, Data dictionary, text file etc. in such a place and location that all desired Alpha 5 windows, users (on the same system), network users have a common access to it. It will be much slower than a typical value, as it is essentially file based, so minimize reads/writes where possible.

In general, do not write to the Data dictionaries and Adb files as these are really for development, not dynamic usage. Windows Registry is also a bad idea, as it is cluttered enough, and there is always a risk of corrupting windows when writing to the registry if system should crash.

Databases and Text files in the appropriate folders are the best way for Alpha 5

[G Gabriel]

Re: A new variable scope

Thanks to everyone responding.
Yes, yes, yes.. you could do it in many different ways..

So far we've got:
application cookies (need more specifics) and
save to a text file

I will throw in another one:
Save to a table...(I don't know if that's what Ira meant as well).

BUT..

It's much much easier than that..

[aschone]

Re: A new variable scope

Not sure why you would want to add the complexity of a table into the fray. when a simple text file can handle the info for you.

I believe that the table would need to provide a needed benefit prior to wanting to implement one in this fashion. Either I would need to take advantage of the tables ability to index/query or sort based on different fields. But All of that could be handled within an array just as easily.

[G Gabriel]

Re: A new variable scope

Andrew:
This is not how I would do it, I am just throwing few more ideas along the line of what was suggested but that's not my way of doing it, none whatsoever.

[aschone]

Re: A new variable scope

O, ok.

How would you do it then? I figured sense you posed the question you wanted to know, but from your responses I am assuming that you already know how you would do it.

[G Gabriel]

Re: A new variable scope

I guess I became known for these brainteasers that some find very annoying while others find very challanging and enlightening..

How about if we just let it ride a little longer for those who like a little challange and who like to figure things out on their own? can you bear with me a little longer?

[csda1]

Re: A new variable scope

Hi Andrew,

Not sure why you would want to add the complexity of a table into the fray. when a simple text file can handle the info for you.

I believe that the table would need to provide a needed benefit prior to wanting to implement one in this fashion. Either I would need to take advantage of the tables ability to index/query or sort based on different fields. But All of that could be handled within an array just as easily.

A table (I said database earlier, but meant it in the generic or Alpha Four terminology of a table/dbf file) is better if multiple users need to share the data. It takes care of the sharing issues. If you used a text file, then when suppose 1st 1 person reads, then another person. 1st person modifies file, and writes. 2nd person modifies files and writes. All of person 1's values are then lost. If, on the other hand, you are the only one using the file, then a text file is OK.

An array goes away the moment you leave Alpha Five. If you want it to still be there next time, it better be stored in something that doesn't go away.

Also, you could also store data in windows environment variables, but this memory space goes away when you shutdown windows, and also very often is not configured for sufficient space to hold much data in many (maybe most) computers.

Using Alpha 5 functions to save values in the database (ADB/ALB/ALM/ALX files) or Table/Set Dictionaries is a bad idea for the reasons outlined earlier.

[aschone]

Re: A new variable scope

Hi Andrew,




A table (I said database earlier, but meant it in the generic or Alpha Four terminology of a table/dbf file) is better if multiple users need to share the data. It takes care of the sharing issues. If you used a text file, then when suppose 1st 1 person reads, then another person. 1st person modifies file, and writes. 2nd person modifies files and writes. All of person 1's values are then lost. If, on the other hand, you are the only one using the file, then a text file is OK.

An array goes away the moment you leave Alpha Five. If you want it to still be there next time, it better be stored in something that doesn't go away.

Also, you could also store data in windows environment variables, but this memory space goes away when you shutdown windows, and also very often is not configured for sufficient space to hold much data in many (maybe most) computers.

Using Alpha 5 functions to save values in the database (ADB/ALB/ALM/ALX files) or Table/Set Dictionaries is a bad idea for the reasons outlined earlier.

Very true on multiple users using the same text file. Seems to me though that a table would do the same thing. In either case you would need to distinguish which variable is assigned to which user. So the current user only modifies the variables assigned to them.

For the arrary I was only mentioning that for manipulation of the data. I wasn't very clear there. You can read the text file into an arrary, then use the arrary sorts to mimic the table sorts.

In the end, if you want the info to persist after a system reboot, you need to store it in a file. The question that I see truly being asked here is, what kind of file do you use.

[martinwcole]

Re: A new variable scope

I've been doing this with the registry for several years.

I have apps where the user jumps from one adb to another and the variables are retrieved in the autoexec.

[G Gabriel]

Re: A new variable scope

The question that I see truly being asked here is, what kind of file do you use.

No, quite the opposite.
So far, all responses point in that direction. I intentionally skirted the above-mentioned suggestions to avoid any blood-shedding debates, but I guess it's unavoidable.

You cannot preserve a variable, because if you do, at least from a technical point of view, it�s no longer a variable. If it becomes part of the permanent records of a table or a database somewhere somehow, by definition, it is no longer a variable.

If you hire a temp then give her a full time job, she is no longer a temp.

Variables are meant to occupy a TEMPORARY placeholder for TEMPORARY usage. These placeholders are wiped out once you leave alpha.

So my question, stated differently is, how do you wipe out these placeholders, i.e. wipe out the variables, but yet preserve them?

It sure sounds like a schizophrenic exercise in dichotomy, doesn't it?

[Tbaker]

Re: A new variable scope

So the question is: can you somehow retool or genetically engineer a variable to make it survive after you exist alpha?

The answer is yes.

Not only it will survive after you exit alpha, it will do so if you exit Windows, if you turn off the power to your machine, to the whole building or the entire neighborhood.

Gabe:

You now have me really confusedwith your last post.

I read some excellent suggestions in this post about where and how to store variables.

Are you still saying "the answer is yes or is the answer no"

Tom