| Re: static variable mayhem [message #11683 is a reply to message #11682] |
Tue, 12 May 1998 00:00  |
Theo Brauers
Messages: 58
Registered: November 1997
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Member |
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Hi:
you may the following:
FUNCTION foo, x
COMMON foo, called
; look if called is defined, what ever value it has!
IF n_elements(called) EQ 0 THEN BEGIN
; define called
called=1
RETURN, x-1
ENDIF
RETURN, x+1
END
I hope it solves your problem.
Theo
T Bowers wrote:
>
> Hi.
> I'm trying to do something very simple, but IDL 5.02 is fighting me. I'm
> trying
> to have what would be a static variable in c/c++ in a function set as a flag
> so
> that it is initialized when i come in, like so:
>
> function foofunc, x
> ;In c/c++ I would put this next line to init my flag the 1st time this fn
> is called
> ; from foopro below.
> ;static int firstTimeInFooFunc = 1; ;Set to 1 ONLY the 1st time foofunc
> called
>
> if (firstTimeInFooFunc) then begin
> firstTimeInFooFunc = 0 ;Set so this'll never happen again on subsequent
> calls
> return, x = x - 1
> endif $
> else return, x = x + 1
> end
>
> pro foopro
> x = foofunc(0)
> print, x
> x = foofunc(x)
> print, x
> x = foofunc(x)
> print, x
> return
> end
>
> the output I want is:
> -1
> 0
> 1
>
> I tried:
> function foofunc, x
> common CBlock, firstTimeInFooFunc = 1
> ...
>
> but IDL won't let me initialize firstTimeInFooFunc like this.
> Then I thought probably IDL would initialize it for me automatically to 0.
> So i just changed the code to:
>
> ...
> function foofunc, x
> common CBlock, firstTimeInFooFunc ;I think this'll init to 0
>
> if (NOT firstTimeInFooFunc) then begin ;init'd to 0, so I'll just NOT
> the bastard
> firstTimeInFooFunc = 1 ;Set so this'll never happen again on subsequent
> calls
> return, x = x - 1
> endif $
> ...
>
> No such luck. It compiles, but when I single step to this line, I get
> % Variable is undefined: FIRSTTIMEINFOOFUNC (CBLOCK).
> % Execution halted at: FOOFUNC blah, blah, blah
>
> I'm *sure* I'm missing something here. Doesn't IDL have static variables?
> Can anybody help, please?
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