| Re: Passing optional parameters through a wrapper routine [message #18915 is a reply to message #18840] |
Thu, 10 February 2000 00:00   |
edward.s.meinel
Messages: 12
Registered: May 1999
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Junior Member |
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In article <950129121.690143@clam-55>,
"Mark Hadfield" <m.hadfield@niwa.cri.nz> wrote:
> That's an interesting point David. The first few lines
> of my routines tend to look something like this:
>
> if n_elements(arg1) then message, 'You haven't defined arg1'
...
> 2. The principle that in scientific programming
> (as opposed, say, to Web page programming)
> it is much better for programs to crash than to continue
> and return bad data.
Ugh, I *hate* MESSAGE. Why cause a crash when it is easy to exit nicely?
How about:
IF N_ELEMENTS(arg1) EQ 0 THEN BEGIN
print, 'You haven't defined arg1'
RETURN
ENDIF
or even:
IF N_ELEMENTS(arg1) EQ 0 THEN BEGIN
dummy = DIALOG_MESSAGE('You haven't defined arg1')
RETURN
ENDIF
This way the user gets the message, but the program doesn't crash. This
is especially helpful when the procedure is used in a widget -- I don't
have to manually clean up everything before trying again.
> if size(arg2, /TNAME) ne 'STRING' then message, 'Arg2 must be string
> specifying the file name'
...
> if in doubt, stop and call for help.
Right, but you can stop and ask for help without forcing a crash. How
about:
IF SIZE(arg2, /TNAME) NE 'STRING' THEN BEGIN
; Oooops! forgot the file name.
arg2 = DIALOG_PICKFILE(set_the_appropriate_keywords)
IF arg2 EQ '' THEN BEGIN
dummy = DIALOG_MESSAGE( $
'You must provide a file name as the second argument')
RETURN
ENDIF
ENDIF
Ed Meinel
Sent via Deja.com http://www.deja.com/
Before you buy.
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