| Re: Yet again, The Sky is Falling! [message #53039 is a reply to message #52940] |
Mon, 12 March 2007 15:19   |
Foldy Lajos
Messages: 268
Registered: October 2001
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Senior Member |
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On Mon, 12 Mar 2007, Sven Geier wrote:
> mgalloy@gmail.com wrote:
>
>> I'm talking about two parameters that are both passed a single named
>> variable (like Paul's mypro example). While legal, I don't think this
>> is a good technique for clear code.
>>
>
> ...and as usual there's exceptions where this is a perfectly good thing to
> do. I have a routine in front of me that dynamically improves a "guess" of
> some number. It takes an input and an output parameter and in almost all
> cases you want to give it the same variable there. Schematically like this
>
> x = someOldGuess
> improve,x,x
>
> where "improve" takes the first "x" as its input, copies the values to a
> local variable, performs a bunch of magic and returns the result in
> the "second x". From the outside, the variable "x" simply has a new,
> improved value (which is the purpose of "improve'). However, there can be
> extreme cases where one might want to have a little more introspection and
> where one might want to check the returned value before using it and in
> that case one can make it
>
> improve,x,y
> if (some test here) then x=y
>
> or such.
>
> I second David's statement that one of the nice things about IDL is that one
> can do all these weird things. As someone once said (about C++, I
> think) "all the power and all the elegance of a hand grenade": It ain't
> always pretty but it gets things done.
>
> - S
>
> --
> http://www.sgeier.net
> My real email address does not contain any "Z"s.
>
You can do that, but be cautios. Try this eg.:
pro improve, a, b
b=a+1
if a eq b then print, 'The Sky is Falling! (a is equal to a+1!)'
end
x=1
improve, x,x
I think it is better to use an improve function: x or y =improve(x).
regards,
lajos
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