| scopes [message #85951] |
Fri, 20 September 2013 14:28  |
spluque
Messages: 33
Registered: September 2013
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Member |
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Hi,
Using the following script to convert calendar date to day of year (test.pro):
FUNCTION calendar2doy, year, month, day
jd=julday(month, day, year)
caldat, jd, Null, Null, year
doy=string(jd - julday(12, 31, year - 1), format='(i03)')
RETURN, doy
END
PRO TEST
year=2011
mon=10
day=15
DOY=calendar2doy(year, mon, day)
RETURN
END
I expected the variable year in the TEST procedure to remain as defined (the long integer 2011), but this is what I see after calling the call to calendar2doy with a breakpoint at the RETURN line:
IDL> .run "test.pro"
% Compiled module: CALENDAR2DOY.
% Compiled module: TEST.
IDL> breakpoint,'test.pro',14
IDL> test
% Compiled module: JULDAY.
% Compiled module: CALDAT.
% Breakpoint at: TEST 14 test.pro
IDL> print, year
2012
What am I missing?
Cheers,
Seb
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| Re: scopes [message #85952 is a reply to message #85951] |
Fri, 20 September 2013 14:44  |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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spluque@gmail.com writes:
>
> Hi,
>
> Using the following script to convert calendar date to day of year (test.pro):
>
> FUNCTION calendar2doy, year, month, day
> jd=julday(month, day, year)
> caldat, jd, Null, Null, year
> doy=string(jd - julday(12, 31, year - 1), format='(i03)')
> RETURN, doy
> END
>
> PRO TEST
> year=2011
> mon=10
> day=15
> DOY=calendar2doy(year, mon, day)
> RETURN
> END
>
>
> I expected the variable year in the TEST procedure to remain as defined (the long integer 2011), but this is what I see after calling the call to calendar2doy with a breakpoint at the RETURN line:
>
> IDL> .run "test.pro"
> % Compiled module: CALENDAR2DOY.
> % Compiled module: TEST.
> IDL> breakpoint,'test.pro',14
> IDL> test
> % Compiled module: JULDAY.
> % Compiled module: CALDAT.
> % Breakpoint at: TEST 14 test.pro
> IDL> print, year
> 2012
>
> What am I missing?
Ah, yes, I've seen this before. It's weird. :-)
The problem comes about in the way you are calling CalDat:
caldat, jd, Null, Null, year
You are using the same variable for the day and month. This causes
CalDat great confusion! If you use different variables, you will get
what you expect.
caldat, jd, Null1, Null2, year
It must be something about variables getting updated in a particular
sequence or something. I don't understand exactly what is happening, but
I remember struggling for hours with exactly this thing one time. ;-)
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.idlcoyote.com/
Sepore ma de ni thue. ("Perhaps thou speakest truth.")
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| Re: scopes [message #86158 is a reply to message #85954] |
Sun, 13 October 2013 20:20 |
SonicKenking
Messages: 51
Registered: October 2010
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Member |
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On Saturday, September 21, 2013 8:00:27 AM UTC+10, spl...@gmail.com wrote:
> Thanks, David, I followed up at about the same time, just after I played supplying some variable names for month and day. It's mildly annoying to have to do this since one may have no use for them, cluttering the environment.
>
>
>
> Seb
You can do it with the new !NULL variable if you have IDL 8.0+, like this
caldat, jd, !null, !null, year
Correct result. No dummy variables.
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| Re: scopes [message #86165 is a reply to message #85951] |
Tue, 15 October 2013 08:23 |
Matthew Argall
Messages: 286
Registered: October 2011
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Senior Member |
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Variables are passed by reference in IDL. If two output positional parameters reference the same variable name, you are going to have a bad time.
Try this
-----------------------------------
pro test_input_params, a, b
a = 5
b = 4
help, a, b
end
test_input_params, null, null
----------------------------------
It shows that a = a = 4 and that b = a = 4 inside the test program. If I were to later do something with a and b independently, the results would not be independent. I assume that CalDat uses the "month" and "day" parameters when calculating "year", which is why your output is funky.
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| Re: scopes [message #86166 is a reply to message #86165] |
Tue, 15 October 2013 08:41 |
Matthew Argall
Messages: 286
Registered: October 2011
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Senior Member |
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I guess a better example would be this:
----------------------------------------
function test_input_params, a, b
a = 5
b = 4
return, a + b
end
IDL> print, test_input_params(null, null)
8
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