STATIC variables

[ErosOlmi]

Next thinBasic version will have STATIC variables developed.

STATIC variables are variables defined inside FUNCTIONs or SUBs, have local scope (are seen only from inside the function or sub that define it) and maintain theyr value even when function or sub finish its execution.

You will be able to define any STATIC variable of whatever type inside a function or sub.

Regards
Eros

UPDATE:

2008.03.25
Attached a new thinCore version implementing STATIC variables
Also in the zip file an example
2008.03.26
Attached file updated. Fixed STATIC variables passed as function parameters to other function
Attached file updated. Fixed recursive function using STATIC variables

2008.03.27
fix &b (lower case) used to manage binary number representation

[kryton9]

THanks Eros, that is a great feature!

[Petr Schreiber]

Very nice feature,

they can eliminate need for global variables in some cases very nicely,
I am looking forward to it!


Thanks,
Petr

[ErosOlmi]

OK, attached to the first post of this thread a new thinCore.dll thinBasic Core engine implementing STATIC variables.
Still under testing so if you find any trouble please let me know.

Remember: static variables are variables that persists for the life of the running process and have function scope, that is are visible only inside the function implementing them.

Here an example:


'----------------------------------------------------------------------------
' Using static variables
'----------------------------------------------------------------------------

uses "console"


function Test001() as long
'--- Define s static variable that will be used as function execution counter
'--- Every time function is executed, counter is incremented
'--- Static variables are declared only once and are local to the function.
'--- Static variables retain their values as long as the program is running

static Counter as long

'--- Now increment by 1
incr Counter
console_writeline "Counter Inside " & function_name & " is: " & format$(Counter, "000")

end function

function Test002(optional byval SetString as string) as long
'--- Now a test with 2 static variables: one counter and one string array
static Counter as long
static MyArrayOfStrings(10) as string

incr Counter
if Counter <= ubound(MyArrayOfStrings) then
MyArrayOfStrings(Counter) = SetString
console_writeline "String in function " & function_name & " is: " & MyArrayOfStrings(Counter)
end if

end function

'---
dim Counter as double
dim RetValue as long

for Counter = 10 to 1 step -1
console_write "Counter outside is: " & format$(Counter, "000") & " - "
Test001
Test002("Any string " & Counter)
next

console_writeline "All done. Press any key to continue"
console_waitkey

[Petr Schreiber]

Very nice!,

I originally thought you just set special access flags for GLOBALs, but more I think of it, more complex task it had to be.

Thanks a lot,
Petr

P.S. Testing so far goes well, no problems found

[ErosOlmi]

I originally thought you just set special access flags for GLOBALs, ...

;) that was my original idea when I had no ... ideas :D
Than I get a flash and found the way to go.

thinBasic static variables are real static and created in a variable scope connected with the function in which static are declared.

I've not tested all situations so I expect there are some bugs but so far it seems working fine.
I still have to test situations like calling a function with static that call another function that have static or calling recursively a function with static.

Ciao
Eros

[Petr Schreiber]

Hi Eros,

here is one problematic case - passing STATIC as parameter to other function
I get "Variable not defined or mispelled Keyword"



uses "console"

alias console_printline as print

a(5)

console_waitkey

sub a( param as long )
print "-- SUB A"

static myVar as long

myVar = param

b(myVar)

end sub

sub b( param as long )
print "-- SUB B"+STR$(param)

end sub



Thanks,
Petr

[ErosOlmi]

I knew you were a real bug buster!
:P

[kryton9]

Amazing Petr how you seem to be able to find bugs so quickly.

[ErosOlmi]

In reality there are some other bugs for example when a function with static is called many times.

:( Well, some other job to do on STATIC matter but absolutely worth to have them.

[ErosOlmi]

here is one problematic case - passing STATIC as parameter to other function


Problem should be fixed. Get updated attached file in first post of this thread.

Ciao
Eros

[Petr Schreiber]

Thanks Eros,

the bug was easy to find only thanks to your mention about recursion :)

The new version corrected the sample above very well, but I found one more problem, now with that recursion.
It seems STATIC variable can lose its value?



uses "console"

alias console_printline as print

a(1)

console_waitkey

sub a( param as long )

static myVar as long
myVar = param
incr myVar

print $SPC(myVar)+"RECURSE A >>" +STR$(myVar)
if param < 10 then a(myVar)
print $SPC(myVar)+"RECURSE A <<" +STR$(myVar)

end sub


If I would use LOCAL, the output would be correctly:


RECURSE A >> 2
RECURSE A >> 3
RECURSE A >> 4
RECURSE A >> 5
RECURSE A >> 6
RECURSE A >> 7
RECURSE A >> 8
RECURSE A >> 9
RECURSE A >> 10
RECURSE A >> 11
RECURSE A << 11
RECURSE A << 10
RECURSE A << 9
RECURSE A << 8
RECURSE A << 7
RECURSE A << 6
RECURSE A << 5
RECURSE A << 4
RECURSE A << 3
RECURSE A << 2


But with that static I get weird results:


RECURSE A >> 2
RECURSE A >> 3
RECURSE A >> 4
RECURSE A >> 5
RECURSE A >> 6
RECURSE A >> 7
RECURSE A >> 8
RECURSE A >> 9
RECURSE A >> 10
RECURSE A >> 11
RECURSE A << 0
RECURSE A << 0
RECURSE A << 0
RECURSE A << 0
RECURSE A << 0
RECURSE A << 0
RECURSE A << 0
RECURSE A << 0
RECURSE A << 0
RECURSE A << 0


I think it should give the same as first listing.
EDIT: No it should not :D


Thanks,
Petr

[ErosOlmi]

New version attached into first post of this thread.
Fixed recursive calling of functions containing.

Now I want to see what you find ! ;D

[Petr Schreiber]

Thanks Eros,

works great, beware that your cruel treatment of bugs could be spotted by "friends of nature" :D


Thanks,
Petr

[Michael Clease]

Perhaps you could add "Kills all KNOWN bugs" to the slogans ;D

[ErosOlmi]

:D :D

[Michael Hartlef]

Thanks Eros, STATIC variables sound very usefull.