| Re: Static Variables in IDL [message #5996 is a reply to message #5924] |
Thu, 14 March 1996 00:00   |
rivers
Messages: 228
Registered: March 1991
|
Senior Member |
|
|
In article <4i8geg$5fv@vixen.cso.uiuc.edu>, santanu@eehpx22.cen.uiuc.edu
(S Bhattacharyya) writes:
> rivers@cars3.uchicago.edu (Mark Rivers) writes:
>
> Pardon me if I appear a bit obtuse, but I am still a little confused. I am
> under the impression that the common block declaration is equivalent to
> C's global declaration. What I would like to have is a bit of non re-entrant
> code in a standalone function (.pro). I want an IDL .pro that does the
> following::
>
> main()
> {
> for(;;) non_rEntrant();
> }
> non_rEntrant()
> {
> static int block=1;
>
> if (block == 1){
> puts("This is executed only once");
> block=0;
> }
> puts("And this is done over and over again");
> }
>
> The following does exactly the same thing ----------------
>
> pro test
> common SHARE,block
> block=1
>
> repeat begin
> call_procedure,'non_rEntrant'
> endrep until block eq 1
> end
>
> pro non_rEntrant
> common SHARE,block
> if block eq 1 then begin print,'This is executed only once' & block=0 & endif
> print,'And this is done over and over again'
> end
>
> But the two lower level function/pro's are not the same, the
> C version is standalone, how do I make the IDL pro non_rEntrant behave
> in the same way ?
Change your IDL example to the following:
pro test
while (1) call_procedure,'non_rEntrant'
end
pro non_rEntrant
common SHARE,block
if (n_elements(block) eq 0) then begin
print,'This is executed only once'
block=0
endif
print,'And this is done over and over again'
end
The key is n_elements(). If non_rEntrant has never been called then block is
undefined and n_elements(block)=0.
____________________________________________________________
Mark Rivers (312) 702-2279 (office)
CARS (312) 702-9951 (secretary)
Univ. of Chicago (312) 702-5454 (FAX)
5640 S. Ellis Ave. (708) 922-0499 (home)
Chicago, IL 60637 rivers@cars3.uchicago.edu (Internet)
|
|
|
|
comp.lang.idl-pvwave archive
Members
Search
Help
Login
Home
