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Azure

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Joined: 09/11/2017
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Posted: 05:13am 22 Feb 2018

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Think of STATIC as a DIM that is only visible to the SUB/FUNCTION it is declared in.

Great for writing portable routines that need to preserve information between each time it is called.

Grogster

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Joined: 31/12/2012
Location: New Zealand
Posts: 9610

Posted: 05:49am 22 Feb 2018

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Can I please just confirm that STATIC variables are only visible to the routine that called it?

IE: NOT visible to the global code, and also NOT visible to OTHER sub's that do other things. STATIC is 'static' to the routine that created it in the first place, in other words.

If you have a STATIC variable, it obviously is saved to memory somewhere when the sub/function exits. When the sub/function is called again at some point, and the interpreter runs into the STATIC keyword, I assume it then preloads the variable names that match the ones it has stashed in memory somewhere. Is that how it is working?

Smoke makes things work. When the smoke gets out, it stops!

TassyJim

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Joined: 07/08/2011
Location: Australia
Posts: 6283

Posted: 06:06am 22 Feb 2018

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Grogster said Can I please just confirm that STATIC variables are only visible to the routine that called it?

IE: NOT visible to the global code, and also NOT visible to OTHER sub's that do other things. STATIC is 'static' to the routine that created it in the first place, in other words.

Yes, They are LOCAL to the SUB/Function

Grogster said
If you have a STATIC variable, it obviously is saved to memory somewhere when the sub/function exits. When the sub/function is called again at some point, and the interpreter runs into the STATIC keyword, I assume it then preloads the variable names that match the ones it has stashed in memory somewhere. Is that how it is working?

That is correct.

Quote ' returns the elapsed time between keypresses
PRINT timebetweendrinks()

DO
IF INKEY$<>"" THEN
PRINT timebetweendrinks(), TIME$, bottomsup, drinktime
' the two variables remaine at zero outside the function
ENDIF
LOOP

FUNCTION timebetweendrinks()
STATIC bottomsup ' we need to remember the last drink
LOCAL drinktime ' temporary variable
drinktime = VAL(MID$(TIME$,7,2))+VAL(MID$(TIME$,4,2))*60+VAL(MID$(TIME$,1,2))*3600
IF bottomsup = 0 THEN
timebetweendrinks = 0 ' gives a zero time if it is the first call to the function
ELSE
timebetweendrinks = drinktime - bottomsup
ENDIF
bottomsup = drinktime ' save the new drink time
END FUNCTION

I added the two variables STATIC and LOCAL to the print line to show that they both remain at zero outside the function.

JimEdited by TassyJim 2018-02-23

VK7JH
MMedit

Grogster

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Posted: 06:09am 22 Feb 2018

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Marvellous, thanks.

I think I comprehend now.

Smoke makes things work. When the smoke gets out, it stops!

Geoffg

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Joined: 06/06/2011
Location: Australia
Posts: 3292

Posted: 07:36am 22 Feb 2018

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Grogster said But if STATIC is supposed to remain across calls to subs and functions, then STATIC SwState=0 will clear it anyway

No, STATIC SwState=0 will just set the initial value for the variable for the first call to the subroutine. On subsequent calls its value will be whatever its last value was. Actually, setting it to zero was redundant as all variables are set to zero when created (including STATIC variables).

I can see that this could cause confusion so I will make sure that the documentation covers it.

Geoff

Geoff Graham - http://geoffg.net

MicroBlocks

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Joined: 12/05/2012
Location: Thailand
Posts: 2209

Posted: 08:22am 22 Feb 2018

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Static in computer languages means that it is allocated only once and that allocation never changes (remains static) for the entire run of the program, it is also initialized only once.
Exactly the same as a global variable although those can be done with DIM.
A LOCAL variable will be allocated (storage room for the variable in memory) each time a sub or function is called and it is also initialized each time.
LOCAL has scope, meaning that variable is only available within the sub or function.
STATIC is a variation of LOCAL. It is still only available within the sub or function but the storage allocation and initial value is done only once.

Microblocks. Build with logic.

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