| Re: new to IDL - question about modularity [message #54572 is a reply to message #54571] |
Mon, 25 June 2007 08:17   |
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Paul Van Delst[1]
Messages: 1157
Registered: April 2002
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Senior Member |
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David Fanning wrote:
> Josh writes:
>
>> despite having five manuals on IDL in front of me, I'm having some
>> trouble with writing modular code. I think it lies in my lack of
>> understanding of the structure, but hopefully it's a simple issue...
>>
>> I'm using IDL 6.3, and have written a single .pro file that looks
>> like,
>>
>> pro xxx
>> ...
>> end
>>
>> pro yyy
>> ...
>> end
>>
>> pro zzz
>> ...
>> end
>>
>> in an effort to break up the tasks to be done. However, within the
>> zzz procedure I would like to access an array that was built in the
>> xxx procedure. I realize that's not possible, and was hoping for some
>> guidance as to a better way to do this.
>
> The simplest way to do this, and maybe the only way if
> there is really no connection between the three modules
> in your example, is to use a common block to store the array.
A common block? Shock, horror, and gasp! :o0
Just kidding :o) But, I don't think the OP has provided enough information to suggest
them as the first possible solution in a list. I would prefer encapsulation of all the
relevant data in a structure (or object) depending on, among other things, computational
cost, complexity, etc.
- If the array in question that was built in xxx is cheap to construct, then perform that
construction in a separate function/pro and call it where it's needed - in both xxx and zzz.
- If the array built in xxx is *not* cheap to construct, then consider the use of a
structure (think of it like an object, let's call it the "abc" object) to carry all your
information - that is, the result of xxx and the intermediate data that other "abc"
methods may need.
> If there is a connection (e.g., zzz calls xxx), then you
> can pass information around by means of output keywords
> or even pass a pointer variable around that can be filled
> out by individual modules.
>
> There really should be some kind of connection, or these
> procedures shouldn't be in the same file. That is to say,
> the only reason xxx and yyy should be in the same file
> as zzz is that they are utility routines for zzz. Thus,
> a common block is rarely (I almost said never) needed.
> They should be able to pass all their information via
> keywords and parameters. :-)
I reckon a structure is the go. Or maybe even an object depending on the comfort level of
the OP in using them.
cheers,
paulv
--
Paul van Delst Ride lots.
CIMSS @ NOAA/NCEP/EMC Eddy Merckx
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