| _extra keyword [message #43326] |
Fri, 01 April 2005 02:12  |
antonioolita
Messages: 2
Registered: April 2005
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Junior Member |
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How Must I use this keyword?
If I have a procedure
PRO TRY, a,b,_extra=extra
tv, c
END
where the programmer tell me that for extra is available every keyword
of (for example) PLOT,
Can I call simply
TRY, a, b, thick=3
where thick is a valid keyword for PLOT(and therefore for TRY)...
or not?
Thanks for the answers
Antonio
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| Re: _extra keyword [message #43362 is a reply to message #43326] |
Thu, 07 April 2005 12:52  |
Michael Wallace
Messages: 409
Registered: December 2003
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Senior Member |
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> The problem (and beauty) of _EXTRA is that unknown
> keywords are silently ignored by the procedures that
> use this mechanism. In practice, this means that if you
> misspell a keyword, no one ever complains, but the keyword
> has no effect, either. I strongly suspect that is your
> problem.
>
> One way to handle this problem is to use the _STRICT_EXTRA
> keyword (in place of _EXTRA) on the last procedure or function
> in the keyword inheritance chain. The _STRICT_EXTRA *will*
> complain if it gets a keyword it doesn't understand, so you
> can use this to trap for misspelled keywords.
Just as a programming style note, when I'm in a routine which only
passes extra keywords to one other routine, I always use _STRICT_EXTRA.
That guarantees me that if I mistype something or get a wrong
keyword, the error will be caught.
The only time I don't use _STRICT_EXTRA is if I'm going to pass the
extra arguments to at least two other routines. In this case you'd want
the first routine to ignore the keywords associated with the second and
vice versa. However, I only recommend doing this when it's really
necessary. I've found that extra keywords are much easier to debug and
maintain when you're able to use _STRICT_EXTRA.
-Mike
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| Re: _EXTRA KEYWORD [message #68619 is a reply to message #43326] |
Wed, 11 November 2009 19:01 |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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Michael Galloy writes:
> Well, I would say you have the choice of _EXTRA and _REF_EXTRA on the
> boat and the choice between _EXTRA and _STRICT_EXTRA on the line.
You can have as many on the line as you like (and your
license allows), but the _STRICT_EXTRA better be on
the *end* of the line if it is going to do any good.
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Sepore ma de ni thui. ("Perhaps thou speakest truth.")
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| Re: _EXTRA KEYWORD [message #68620 is a reply to message #43326] |
Wed, 11 November 2009 18:54 |
Michael Galloy
Messages: 1114
Registered: April 2006
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Senior Member |
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David Fanning wrote:
> ben.bighair writes:
>
>> Even if my analogy is correct, it might be too simplistic to be
>> complete. Hope it helps.
>
> I would just add that _EXTRA and _REF_EXTRA are always
> used on the boat (the procedure or function definition
> line), and _STRICT_EXTRA is always used at the end
> of the line. ;-)
Well, I would say you have the choice of _EXTRA and _REF_EXTRA on the
boat and the choice between _EXTRA and _STRICT_EXTRA on the line.
Mike
--
www.michaelgalloy.com
Research Mathematician
Tech-X Corporation
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| Re: _EXTRA KEYWORD [message #68623 is a reply to message #43326] |
Wed, 11 November 2009 17:36 |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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ben.bighair writes:
> Even if my analogy is correct, it might be too simplistic to be
> complete. Hope it helps.
I would just add that _EXTRA and _REF_EXTRA are always
used on the boat (the procedure or function definition
line), and _STRICT_EXTRA is always used at the end
of the line. ;-)
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Sepore ma de ni thui. ("Perhaps thou speakest truth.")
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| Re: _EXTRA KEYWORD [message #68624 is a reply to message #43326] |
Wed, 11 November 2009 16:23 |
ben.bighair
Messages: 221
Registered: April 2007
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Senior Member |
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On Nov 11, 5:47 pm, mankoff <mank...@gmail.com> wrote:
> On Nov 9, 1:09 am, Reimar Bauer <R.Ba...@fz-juelich.de> wrote:
>
>> dandan schrieb:
>
>>> Hi, everyone,
>>> Dose _EXTRA pass the keywords from the caller to called routine or the
>>> opposite?
>
>> You may be also interested into the _REF_EXTRA keyword.
>
>> The presence of a name in the _REF_EXTRA value indicates that a keyword
>> of that name was passed, and its value is available to be passed on in a
>> function or procedure call (using either _EXTRA or _STRICT_EXTRA).
>
>> cheers
>> Reimar
>
> I still have not entirely wrapped my head around _EXTRA, _REF_EXTRA,
> and _STRICT_EXTRA despite numerous readings of discussions on this
> group about these keywords.
>
> Does anyone have a graphical explanation of these? A flow-chart with
> arrows and diamonds and YES/NO keywords perhaps? I have a feeling that
> would get the concept across. If not, perhaps I'll take what I do
> understand of these keywords and try to create such a chart.
>
> -k.
Hi,
I am not sure if this analogy is correct, but it works for my limited
use. Assume that _EXTRA and _REF_EXTRA are fishing lines.
_REF_EXTRA has bait and a hook so you can pull things back. A
_REF_EXTRA is passed by reference - so you can send in a value but if
it is modified (like an output keyword) then the reference will
reflect that change. This is how you can land the trout, so to
speak.
On the other hand, _EXTRA has bait but no hook so you can send things
down in but not get them back. That is because _EXTRA is passed by
value - any modifications the trout makes under water are hidden from
you.
_STRICT_EXTRA is just like _EXTRA, but if you use the wrong kind of
bait the trout will complain (or issue an error and stop if they know
any IDL).
Even if my analogy is correct, it might be too simplistic to be
complete. Hope it helps.
Cheers,
Ben
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| Re: _EXTRA KEYWORD [message #68628 is a reply to message #43326] |
Wed, 11 November 2009 14:47 |
mankoff
Messages: 131
Registered: March 2004
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Senior Member |
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On Nov 9, 1:09 am, Reimar Bauer <R.Ba...@fz-juelich.de> wrote:
> dandan schrieb:
>
>> Hi, everyone,
>> Dose _EXTRA pass the keywords from the caller to called routine or the
>> opposite?
>
> You may be also interested into the _REF_EXTRA keyword.
>
> The presence of a name in the _REF_EXTRA value indicates that a keyword
> of that name was passed, and its value is available to be passed on in a
> function or procedure call (using either _EXTRA or _STRICT_EXTRA).
>
> cheers
> Reimar
I still have not entirely wrapped my head around _EXTRA, _REF_EXTRA,
and _STRICT_EXTRA despite numerous readings of discussions on this
group about these keywords.
Does anyone have a graphical explanation of these? A flow-chart with
arrows and diamonds and YES/NO keywords perhaps? I have a feeling that
would get the concept across. If not, perhaps I'll take what I do
understand of these keywords and try to create such a chart.
-k.
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