SHARED doesn't share variables from the non-main-scope

[rudd68]

Hello,

the keyword "Shared" doesn't work, but it isn't forbidden in the documentation:

Code: Select all

Procedure.s Create_Display_Text()
  Shared Element
  Debug Element  
  Text.s = "Random_Element is: " + Str(Element)
  ProcedureReturn Text
EndProcedure

Procedure Random_Element()  
  Element.l = Random(100) + 1
  Debug Element  
  Debug Create_Display_Text()
EndProcedure

; main program

Random_Element()

End

Please don't correct the documentation but enlarge the functionality of the keyword "Shared".

Greetings.

[ts-soft]

You have to use shared in all procedures, you use it.

Code: Select all

Procedure.s Create_Display_Text()
  Shared Element
  Debug Element 
  Text.s = "Random_Element is: " + Str(Element)
  ProcedureReturn Text
EndProcedure

Procedure Random_Element() 
  Shared Element
  Element = Random(100) + 1
  Debug Element 
  Debug Create_Display_Text()
EndProcedure

; main program

Random_Element()

End 

And it is recommed to define the Shared Var in the MainScope!

[rudd68]

Thank you ts-soft.

But the first definition of the variable "Element" is in the procedure "Random_Element()".

The behavior of "Shared" is differently to written in the documentation.

I have 1100 lines of code, 15 procedures, many variables. Your solution expands the main program code and the code in the higher procedures. I don't want this.

Either I use parameters in the procedure calls or I use the keyword "Global". "Shared" is too restricted.

[netmaestro]

You have to use shared in all procedures, you use it.

You only need to use the keyword Shared in those procedures that need access to the var. Or, alternatively, define the var in the main scope and use Shared in one or more procedures that need access. If you have 15 procedures, by no means do all procedures need the definition. That would mimic Global. One common use for it is if you have a procedure and you're calling something like EnumChildWindows() or such from it. You would use Shared to allow those two procs to know a particular variable, where none of the others know it or need to:

Code: Select all

Procedure four( )
  Debug "four: "+Str(x) ; not shared here!
EndProcedure

Procedure three( )
  Debug "three: "+Str(x) ; or here!
  four()
EndProcedure

Procedure two()
  Shared x
  Debug "two: "+Str(x)
  three()
EndProcedure

Procedure one()
  Shared x
  x=10
  Debug "one: "+Str(x)
  two()
EndProcedure

one()

As I hope is obvious by now, a Shared variable must exist in a minimum of two places in your code to make any sense (and actually do something useful). If it exists in only one place, there is nobody to share with. This is what was wrong with the posted snippet.

The EnumChildWindows is a good example because the EnumProc can't return anything. You want to know something from it, you share a var in the caller and the EnumProc, then let EnumProc set it. The caller receives it because of Shared.

I hope this helps to clear it up for you, as Shared isn't bugged and is quite useful just as it is.

@ts-soft: I know you understand all this, I think your english let you down a bit on this one

[Vera]

@netmaestro
your description and example are very impressionably and would be a fine addition to the IDE-help

THANKS
also for asking

@ rudd68
what would you think about changing the thread-title into something like: 'How SHARED works in sub-procedures'

greetings ~ Vera

[rudd68]

Thank you netmaestro.

Shared must exist in a minimum of two places in your code to make any sense (and actually do something useful). If it exists in only one place, there is nobody to share with.

I doesn't agree with you. Please see the first example in the "Shared" documentation. There is only one "Shared" keyword. It shares the variable "a" from the main program to the procedure.

The solution by ts-soft and your example shares the variable from the main program down to all procedures and sub-procedures which have the "Shared" keyword. If the variable is not defined in the main program then it is automatically (implicit) defined at the first "Shared" keyword. The evidence: Use "EnableExplicit" and the first "Shared" keyword (in the logical highest procedure) gives an error ("Variables must be defined").

I doesn't want to share a variable from the main program. I want to share a variable, which is first defined in a procedure. This isn't excluded by the documentation.

@vera:
netmaestro's explanation is only partly correct.

I doesn't want rename the title, because "Shared" doesn't works in sub-procedures, if the variable is first defined in the caller procedure.

[netmaestro]

I doesn't agree with you. Please see the first example in the "Shared" documentation.

The keyword Shared doesn't belong in the main scope, but the variable must exist there if you want to share it between main scope and a proc. Trust me, there's no bug here and the doc is right.

Please bring stuff like this up in Coding Questions.

[rudd68]

I think it is a bug or an inaccurate documentation. If it is not a bug then it is my feature wish (and the documentation should be updated.)

Greetings.

[Fred]

It's the intended behaviour, shared is only applicable to one procedure.

[freak]

> I want to share a variable, which is first defined in a procedure. This isn't excluded by the documentation.

It is not explicitly excluded, but the documentation also doesn't say you can do that. If we try to document everything you _can't_ do with PB, then the help will get very large

[Little John]

Just a small comment, because the title of this thread has the potential for confusing newbies:

SHARED doesn't work in sub-procedures

In PB, there are procedures, but no sub-procedures.
A sub-procedure would be a procedure inside of another procedure.

Regards, Little John

[rudd68]

@fred, freak: Thank you for your posts. So I know that the topic has reached you.

@Little John: If procedure "One()" calls procedure "Two()", then procedure "Two()" isn't a sub-procedure? How would you describe procedure "Two()" (I'm from germany and I doesn't have the correct english word)?

A sub-procedure would be a procedure inside of another procedure.

There are sub-procedures in other programming languages like this ???:

Code: Select all

Procedure one()

; code of procedure one()

  Procedure two()
  
  ; code of procedure two()
  
  EndProcedure ; ends procedure definition two()
  
  ; code of procedure one()
  
EndProcedure ; ends procedure definition one()

  

Is there a meaning for it?

Greetings.

[Little John]

@Little John: If procedure "One()" calls procedure "Two()", then procedure "Two()" isn't a sub-procedure?

According to my understanding: no.

How would you describe procedure "Two()"

I'd call (no pun intended) procedure "One()" the caller, and procedure "Two()" the callee.

(I'm from germany and I doesn't have the correct english word)?

I'm not a native English speaker, either. However, IMHO that term carries the risk of creating confusion. And I've never read the term "sub-procedure" in connection with PureBasic. In the docs and everywhere it always just reads "procedure".

A sub-procedure would be a procedure inside of another procedure.

There are sub-procedures in other programming languages like this ???:

Code: Select all

Procedure one()

; code of procedure one()

  Procedure two()
  
  ; code of procedure two()
  
  EndProcedure ; ends procedure definition two()
  
  ; code of procedure one()
  
EndProcedure ; ends procedure definition one()

  

Yes, there are; for instance in the programming language Pascal. I personally never had any need for that, though.

Regards, Little John

[rudd68]

OK, how can I change the topic title?

[Vera]

Hi,

just go to your first posting and click 'edit' and you can change the title as well