scope of variables

[ptitjoz]

Hello

I try to transform a FreePascal program into Bacon
but  I have a problem.
Variables of the same name do not seem to work in Global and Local

here un little example :

In FreePascal

program LocalGlobal;

var i: integer; //scope global

procedure testlocal();
var i: integer; // scope local
begin
i:=10;
writeln('local ',i);
end;

//Main -----------------
begin
i:=100;
writeln('global ',i);
testlocal();
writeln('global ',i);
readln;
end.The result

global 100
local 10
global 100

In bacon

OPTION EXPLICIT TRUE
GLOBAL i TYPE NUMBER

SUB SubLocal
LOCAL i TYPE NUMBER
i=10
PRINT "local ";i
END SUB

'Main
i=100
PRINT "global ",i
sublocal()
PRINT "global ",i
END
The result

Syntax error: variable 'i' in LOCAL statement at line 6 in file '/home/joz/Bacon/Tests/local_global.bac' was defined previously!

Regards

[vovchik]

Dear ptitjoz,

I think BaCon is working very properly here, and EXPLICIT tells us. GLOBAL means the var can be seen everywhere - in SUBs and FUNCTIONs too - so a declaration using a var name that has been made visible to every procedure cannot be redefined in a SUB. Peter will give us the authoritative answer...

With kind regards,
vovchik

[Pjot]

Hi ptitjoz,

BaCon does not support variable shadowing. This is to prevent errors where variables with a global scope (this is the default in BaCon) mix up with variables with local scope.

BR
Peter

[ptitjoz]

Hello, Peter and vovchik

Thank you for your answers.

I thought that declaring declare a variable in Local and / or Global avoided problems
This allows several developers to develop their own routines without taking care of others.

For example if I use Hug.bac there are variables that I can not use anymore. As I have not written hug.bac (or others) it is sometimes embarrassing. The solution is perhaps for each developer prefixed its variables by a code?

Regards

[vovchik]

Dear ptitjoz,

I had thought about that problem too, but your solution is a good one. I think I will implement it in future. Thanks for the idea. It is simple and easy.

With kind regards,
vovchik

[Pjot]

Mar 11, 2018 16:11:00 GMT 1 ptitjoz said:

I thought that declaring declare a variable in Local and / or Global avoided problems
This allows several developers to develop their own routines without taking care of others.

Using the LOCAL statement consequently within functions actually will prevent that you run into errors. Mixing globals and locals will 'lead to confusion', as the Wikipedia article mentions.

Mar 11, 2018 16:11:00 GMT 1 ptitjoz said:

For example if I use Hug.bac there are variables that I can not use anymore. As I have not written hug.bac (or others) it is sometimes embarrassing. The solution is perhaps for each developer prefixed its variables by a code?

Best practice is of course to avoid global variables altogether. The HUG context uses global variables but all of them are prefixed by 'hug_' or 'HUG_'. Feel free to improve the implementation and propose a better version!

Best regards
Peter

[ptitjoz]

Hello Peter
Thank you for all these explanations.

Regarding hug when I put the option EXPLICIT
I have errors. For example

Syntax error: OPTION EXPLICIT forces explicit variable declaration at line 402 in file 'hug.bac'!

If I correct line 402 in my version of hug.bac, other errors appear on other lines ...

Is it possible for a new version to include the declaration of variables that have been forgotten?

Regards

Joz

[vovchik]

Dear Joz,

Peter and I have already discussed this and an official fix will be out soon, I think. In the interim, you can use my fixed version. As I recall (I did this more than a week ago), three variables were involved.

With kind regards,
vovchik

Attachments:

hug.bac.tar.gz (17.69 KB)

[Pjot]

Dear ptitjoz,

Alternatively, you can put OPTION EXPLICIT after the line which includes hug.bac.

BR
Peter

[ptitjoz]

Hello everyone

Thanks for modified hug.bac and thanks for the different explanations.
I thought the OPTION EXPLICIT place did not really matter. I did not think the code analysis was sequential.

Regards