Variable variables

[fenyctis]

Heh, like the topic title.

So what I'm looking for is how to have variable variables:

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var{variable} = test
As in:
var987 = test1
var134 = test2

As in: creating variables during the programme execution with variable names.

I realize this might be a little unclear..

~fenyctis

[srod]

No chance!

Once a program is compiled, all variable names lose their meaning and translate to locations within the computers memory (the heap, the stack etc.)

The closest you'll get is to use an array or a linked list or perhaps even allocate some memory etc.

Of course, you could probably hack something together at the preprocessor stage, perhaps with macros etc.

[SunSatION]

I think you should us arrays in this case.

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Dim var(1000)
varentry = 987
var(varentry) = test1

;Here is to show you that you can change the variable
varentry = 987-853 ; which is equal to 134
var(varentry) = test2

I also think that variable variables are not possible to create

[fenyctis]

No chance!

Once a program is compiled, all variable names lose their meaning and translate to locations within the computers memory (the heap, the stack etc.)

The closest you'll get is to use an array or a linked list or perhaps even allocate some memory etc.

Of course, you could probably hack something together at the preprocessor stage, perhaps with macros etc.

I remember mIRC, in which you could create such variables:

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%var $+ 576 = test

would result in

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%var576 = test

[fenyctis]

I think you should us arrays in this case.

Code: Select all

Dim var(1000)
varentry = 987
var(varentry) = test1

;Here is to show you that you can change the variable
varentry = 987-853 ; which is equal to 134
var(varentry) = test2

I also think that variable variables are not possible to create

The numbers are actually ClientIDs of connecting clients and I want to store some information they pass on (username, hostname etc.) Maybe you've got a good idea?

[SunSatION]

Well, mIRC is not a compiler. That's the only reason why that's allowed. With mIRC scripting, variables are not stored in the data segment, but saved in an ini file

In that case, you can use Multidimensional array

Maybe this is not so perfect, but it gives you some hints

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 dim var(5000,5000,5000,5000)

such that you can save 4 parameters for the given clientID

I noticed that ClientIDs are given in multiples of 4(at least on v3.94). So, if you wish to save space, just divide them by 4(that's what I did).

[fenyctis]

Well, mIRC is not a compiler. That's the only reason why that's allowed. With mIRC scripting, variables are not stored in the data segment, but saved in an ini file

XD Good one.

[srod]

Yes, but unless I'm mistaken, mIRC is not a compiler.

The only way you'll be able to implement something along these lines, is before compilation, e.g. with a macro.

**EDIT - too slow!

[fenyctis]

Yes, but unless I'm mistaken, mIRC is not a compiler.

The only way you'll be able to implement something along these lines, is before compilation, e.g. with a macro.

**EDIT - too slow!

The numbers are actually ClientIDs of connecting clients and I want to store some information they pass on (username, hostname etc.) Maybe you've got a good idea?　I'm afraid of databases, because they require third-party software other people may not have. Having INI files storing these variables is unsafe and requires a lot of writing to the harddrive if my server is busy.

[SunSatION]

Or else, if you were in mIRC scripting and don't want to use Multidimensional array, make something like $token in mIRC with PureBasic.

[srod]

Assuming you're writing all this in Purebasic, then I wouldn't worry about databases. If I've understood correctly, then you could use SQLite easily enough - providing the server application is accessing it as if it were a stand alone app. SQLite simply requires that you copy a single .dll file onto the machine running the application; no activex controls, no MSDAC components, no fiddly ODBC setups.

However, providing the number of clients is not huge, why not use an array of structures:

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Structure ClientInfo
  ClientId.l
  Username.s
  Hostname.s
EndStructure

Dim clients.ClientInfo(999) ;Enough storage for 1000 clients.

clients(0)\Username="Bob"

You could even use a linked list instead.

Writing such an array out to an SQLite database is simplicity itself.

[fenyctis]

Assuming you're writing all this in Purebasic, then I wouldn't worry about databases. If I've understood correctly, then you could use SQLite easily enough - providing the server application is accessing it as if it were a stand alone app. SQLite simply requires that you copy a single .dll file onto the machine running the application; no activex controls, no MSDAC components, no fiddly ODBC setups.

However, providing the number of clients is not huge, why not use an array of structures:

Code: Select all

Structure ClientInfo
  ClientId.l
  Username.s
  Hostname.s
EndStructure

Dim clients.ClientInfo(999) ;Enough storage for 1000 clients.

clients(0)\Username="Bob"

You could even use a linked list instead.

Writing such an array out to an SQLite database is simplicity itself.

Doesn't that array require a lot of memory?

[srod]

How many clients are we talking about?

[fenyctis]

How many clients are we talking about?

Never mind, even a thousand clients doesn't consume that much memory.
Say the strings are a max of 30: ((4+30+30)*1000)/1024 = 62kB

Thanks!