A new variable scope

[csda1]

Re: A new variable scope

You do not need to load the script in order to save the new one.

Gabe:
Let me repeat in case you missed it:
If you want to operate in a 1 person, 1 thread operation go ahead, you'll run just fine.

But you can't do any Multi-user, multi-thread, or Multi-process operation properly (meaning without errors) without a proper read-modify-write (Test & Set) in a single indivisible (atomic) operation as it's basis.

When you join the real world that does more than single threaded operations, you'll find that over 60 years of modern age computers are based on and work because of locking mechanisms.

[DaveM]

Re: A new variable scope

Ira,

So if you'd like to dynamically mess with your data dictionaries, the functions include

A5.WRITE_SETTING( Setting_Name as C, Value as C )
A5.READ_SETTING( Setting_Name as C )

and it's big brother versions

A5_LOAD_SETTINGS( Setting_Name as C, Dot_Variable as P [, Dictionary_Name as C ] )
A5_SAVE_SETTINGS( Setting_Name as C, Dot_Variable as P [, Dictionary as C ] )
A5_DELETE_SETTINGS( Setting_Name as C [, Dictionary as C ])

If you'd like to mess up your Windows registry, we also have these functions (although at least these are only available to a single user)

REGISTRY.LOAD_SETTINGS( Registry_Key as C, Dot_Variable as P )
REGISTRY.SAVE_SETTINGS( Registry_Key as C, Dot_Variable as C )
REGISTRY.DROP_SETTINGS( Registry_Key as C )

But if you really want to just waste more time, and slow things down, then use

SCRIPT_LOAD( Script_Name as C [, Password as C ] )
SCRIPT_SAVE(C script_name,C script_code[,C Password])

If I save something to my registry, can another computer share it? If I save something in a script or any data dictionary on my computer, can another computer share it? If I have a variable on my computer it the Alpha memory range, can another computer share it? NO

I believe these would work on a single user system, but that is not what I mean at all. I mean a shared by anyone connected by a shadow to a server would also be able to share a memory space on that server for the use of a variable(maybe more). Without the use of that memory space, then we are relegated to the use of a table since it is the data that goes back and forth.

Maybe if we ever get to a real server system with a direct connection, we can do that. I am sure Alpha has been working on that, but do not know where it stands in the priorities. Suspect the web stuff comes first.

Now, if we all used the webserver, rewrote our apps, and connected by way of intranet, we could do what g thinks in a way. Am I right?

As it stands now, I(as many do) load all company information into vars for quick use wherever needed, but it is all on the user's computer. There are are other vars that get changed repeatedly on the users computer. I cannot dim a var that is universal and changeable by all the computers in a days work, it has to be saved in a table or I have to make another way to the server. Come to think about it, that is possible, but is it worth the traffic that could come from it and it still has to be written to a file.

DaveM

[forskare]

Re: A new variable scope

Ira,

I don't know if you've unblocked Gabe so you are able to see his comments. If not, you should consider unblocking him. It would lower the frustration levels for both of you.

kenn

[csda1]

Re: A new variable scope

If I save something to my registry, can another computer share it? If I save something in a script or any data dictionary on my computer, can another computer share it? If I have a variable on my computer it the Alpha memory range, can another computer share it? NO

Absolutely correct.

I believe these would work on a single user system, but that is not what I mean at all. I mean a shared by anyone connected by a shadow to a server would also be able to share a memory space on that server for the use of a variable(maybe more). Without the use of that memory space, then we are relegated to the use of a table since it is the data that goes back and forth.

I'm not sure how to interpret what you said above.

Any data stored in a file in any format in a shared network location (this could mean as a text file, non-shadowed (Master) data dictionary, shared table, whatever), can be used 100% safely by any other user if, and only if, there is

• a locking mechanism (and is used properly) that provides a Read-Modify-Write operation without interruption from any process, and the use of it is done correctly, or
• You have a server that arbitrates request for the shared resources and decides which processes data gets written (effectively moving the locking process to within the server).

Now, if we all used the webserver, rewrote our apps, and connected by way of intranet, we could do what g thinks in a way. Am I right?

The web doesn't create a magical solution. It's still the same. It's just acting like a client-server

To reiterate, you can't even share correctly a variable between two different threads/processes/users/CPUs etc on the same computer. One process needs to know if a write is potentially in progress from another thread, and this can't be done without a locking mechanism, unless you want to go with the dangerous concept of whoever writes last, wins (with the exception listed below).

Imagine you have 2 computers that both read a current inventory quantity of say, 5 units, and for a line item in order 1 purchases 2 widgets and order 2 purchases 1 widget. If you now save the new inventory quantity from order 1, the new inventory value is 3. Then comes order # 2 (having previously read a 5 units) and writes a new inventory value of 4. The correct value should have been 2.

The reason this works in Alpha 5 posting rules, is that it does a read-modify-write in 1 indivisible operation. At save time it reads the inventory value, decrements the value and writes it back.

Using a table with locking in the correct way can also accomplish this. But you can't do it with code without using something in Alpha or externally that has an implicit or explicit locking mechanisms allowing a read-modify-write (or equivalent like a test and set)

Now a global setting that all users have access to that you are willing to have the last person changing it always be the current value, then it is fine (imagine which screen style sheet to use as a setting). It is shared but not used in a cooperative way, and hopefully it doesn't matter too much what the current value is to the individual user.

This does not need a locking mechanism unless you are changing a group of variables that must be changed all together. Otherwise, someone could read the partially-written values and have read some of them still in the process of change.

I cannot dim a var that is universal and changeable by all the computers in a days work, it has to be saved in a table or I have to make another way to the server. Come to think about it, that is possible, but is it worth the traffic that could come from it and it still has to be written to a file.

The overhead of writing a couple of variables (values) to a table is almost nothing compared to normal traffic from the main data.

[G Gabriel]

Re: A new variable scope

Gabe:
But you can't do any Multi-user, multi-thread, or Multi-process operation properly (meaning without errors) without a proper read-modify-write .

OK.. for the last time:
1-I acknowledged the multi-users issue from the very early begining.
2-As I said in my last post, I'll tell you again: you do not need to load a script in order to save a new one, one-user or multi-user.