| Re: Yet again, The Sky is Falling! [message #53038 is a reply to message #52940] |
Mon, 12 March 2007 15:30   |
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Paul Van Delst[1]
Messages: 1157
Registered: April 2002
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Senior Member |
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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').
But why do that? It makes no difference since you're overwriting the original value of x
anyway. Why not just do
x = someOldGuess
improve,x
where "improve" just modifies "x" internally as required. The only advantage (that I can
see) of
improve,x,x
over
improve, x
is that the former serves to confuse the reader of the code. There may be examples of
exceptions where the construct in question is a good idea, but this isn't one of them.
> 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.
Yes, well, just because something *can* be done....
But I like the analogy - much more graphic than the old "shoot yerself in the foot"
sawhorse. :o)
cheers,
paulv
--
Paul van Delst Ride lots.
CIMSS @ NOAA/NCEP/EMC Eddy Merckx
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