| static variable mayhem [message #11685] |
Mon, 11 May 1998 00:00  |
T Bowers
Messages: 56
Registered: May 1998
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Member |
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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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| Re: static variable mayhem [message #11770 is a reply to message #11685] |
Wed, 13 May 1998 00:00  |
Martin Schultz
Messages: 515
Registered: August 1997
|
Senior Member |
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Theo Brauers wrote:
>
> Hi:
>
> you may try 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
>
... but be careful when you want to assign variables of different length
to the common block (i.e. arrays or structures). Then you'll have to use
pointers, i.e.
commons,pinfo
if (n_elements(pinfo) eq 0) then pinfo=ptr_new()
if (ptr_valid(pinfo)) then *pinfo=data
------------------------------------------------------------ -------
Dr. Martin Schultz
Department for Earth&Planetary Sciences, Harvard University
109 Pierce Hall, 29 Oxford St., Cambridge, MA-02138, USA
phone: (617)-496-8318
fax : (617)-495-4551
e-mail: mgs@io.harvard.edu
Internet-homepage: http://www-as.harvard.edu/people/staff/mgs/
------------------------------------------------------------ -------
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