| Re: Passing zero as a Parameter/ NOT KEYWORD_SET [message #16071 is a reply to message #16067] |
Tue, 29 June 1999 00:00   |
Martin Schultz
Messages: 515
Registered: August 1997
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Senior Member |
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J.D. Smith wrote:
>
>
> That's a bit dangerous. [...]
Indeed ;-)
>
> The best way to proceed is pretend keyword_set() was really
> named is_defined_and_non_zero(). Forget that it's called
> keyword_set().
In fact it is "is_defined_and_uneven" !
Just try to pass var=2 into a routine and print keyword_set(var). Hope,
David will take notice of this in his article.
Another marginal point about setting default values: I recently learned
from someone's code (cannot remember whose), to use
if (n_elements(var) ne 1) then var=default
instead of
if (n_elements(var) eq 0) then var=default
The advantage being that you can prevent program crashes when someone
passes a vector or array in what is supposed to be a scalar.
And, finally: Use keyword_set when you want to make sure the value of a
boolean flag is defined:
flag = keyword_set(flag)
Then, later in the code, it's just
if (flag) then ...
Or value = x+y*(flag), etc. which would crash otherwise.
Regards,
Martin.
|||||||||||||||\\\\\\\\\\\\\-------------------///////////// //|||||||||||||||
Martin Schultz, DEAS, Harvard University, 29 Oxford St., Pierce 109,
Cambridge, MA 02138 phone (617) 496 8318 fax (617) 495 4551
e-mail mgs@io.harvard.edu web http://www-as/people/staff/mgs/
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