| Re: Keyword checking [message #31006] |
Wed, 29 May 2002 09:02  |
R.Bauer
Messages: 1424
Registered: November 1998
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Senior Member |
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Randall Skelton wrote:
Dear Randall,
keyword_set
should only used to test variables to be true or false
arg_present
is used to find out if a parameter is called by reference
this gives true and by value gives false
n_elements
returns the number of elements of a parameter
We have set up a test case in our lessons
I have posted some time ago.
I believe all is clear if you once filled out these forms
regards
Reimar
1)
There are three functions given
FUNCTION test1,minimum=min_val
IF KEYWORD_SET(min_val) THEN RETURN,1 ELSE RETURN,0
END
FUNCTION test2,minimum=min_val
IF ARG_PRESENT(min_val) THEN RETURN,1 ELSE RETURN,0
END
FUNCTION test3,minimum=min_val
IF N_ELEMENTS(min_val) GT 0 THEN RETURN,1 ELSE RETURN,0
END
Fill out the form:
CALL | test1 | test2 |test3
____________________________________________________________ ____
PRINT, testX( ) | | |
____________________________________________________________ ____
PRINT, testX(minimum=0) | | |
____________________________________________________________ ____
PRINT, testX(minimum=10) | | |
____________________________________________________________ ____
PRINT, testX(minimum=-10) | | |
____________________________________________________________ ____
mv=0 & PRINT, testX(minimum=mv) | | |
____________________________________________________________ _____
mv=10 & PRINT, testX(minimum=mv) | | |
____________________________________________________________ _____
PRINT, testX(minimum=mv2) | | |
____________________________________________________________ _____
2)
There are three functions given
FUNCTION test1,min_val
IF KEYWORD_SET(min_val) THEN RETURN,1 ELSE RETURN,0
END
FUNCTION test2,min_val
IF ARG_PRESENT(min_val) THEN RETURN,1 ELSE RETURN,0
END
FUNCTION test3,min_val
IF N_ELEMENTS(min_val) GT 0 THEN RETURN,1 ELSE RETURN,0
END
Fill out the form:
CALL | test1 | test2 |test3
____________________________________________________________ ____
PRINT, testX( ) | | |
____________________________________________________________ ____
PRINT, testX(0) | | |
____________________________________________________________ _____
PRINT, testX(10) | | |
____________________________________________________________ ____
PRINT, testX(-10) | | |
____________________________________________________________ ____
mv=0 & PRINT, testX(mv) | | |
____________________________________________________________ _____
mv=10 & PRINT, testX(mv) | | |
____________________________________________________________ _____
PRINT, testX(mv2) | | |
____________________________________________________________ _____
>
> I have run into a great deal of trouble checking keywords in IDL and I
> thought I would relay my thoughts and frustrations. I am trying to
> prevent a user from passing an undefined variable in a keyword...
>
> Imagine,
>
> pro test, A=a, B=b
> print, n_params()
> print, arg_present(a), keyword_set(a), n_elements(a), size(a,/type)
> print, arg_present(b), keyword_set(b), n_elements(b), size(b,/type)
> end
>
> If I call this routine as:
>
> IDL> .reset
> IDL> test, a=1, b=undefvar
> % Compiled module: TEST.
> 0
> 0 1 1 2
> 1 0 0 0
>
> So, in order to prevent a user from passing junk in a keyword, I have:
>
> pro test, B=b
> if n_elements(b) eq 0 and arg_present(b) eq 1 then $
> message, 'You passed an undefined variable as a keyword'
> if n_elements(b) gt 0 then b = 'passed'
> end
>
> Now,
>
> IDL> .reset
> IDL> test, b=junk
> % Compiled module: TEST.
> % TEST: You passed an undefined variable as a keyword
>
> Surely there must be something simpiler than my 2-step approach ;)
>
> Cheers,
> Randall
--
Reimar Bauer
Institut fuer Stratosphaerische Chemie (ICG-I)
Forschungszentrum Juelich
email: R.Bauer@fz-juelich.de
------------------------------------------------------------ -------
a IDL library at ForschungsZentrum Juelich
http://www.fz-juelich.de/icg/icg1/idl_icglib/idl_lib_intro.h tml
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