| Re: Preferred way to get multiple returns from a function [message #75012] |
Mon, 14 February 2011 13:42  |
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James[2]
Messages: 44
Registered: November 2009
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On Feb 14, 7:03 am, Paul van Delst <paul.vande...@noaa.gov> wrote:
> James wrote:
>> I am writing a function that fits an ellipse to a 2*N array of
>> points. There are three values to return: the center, semi-major
>> axis, and semi-minor axis. This is a simple program, but it brings up
>> a more general question: what is the preferred IDL way to return
>> multiple values from a function?
>
>> Currently, my program returns a structure containing the elements
>> {center, major, minor}. However, a lot of built-in IDL routines take
>> named variable inputs that are set to the appropriate value on output
>> - so instead of something like:
>
>> ellipse_struct = fit_ellipse(points)
>
>> I would have:
>
>> fit_ellipse, points, center, major, minor
>
>> I'm not sure which is better. C programming has taught me to
>> appreciate structures, but I'd like to code in the conventions of the
>> language. Which would you prefer, and why?
>
> Structure.
>
> Why? Because it produces self-documenting code.
>
> Similar to what R.G.Stockwell said,
>
> ellipse.center
>
> doen't require a comment describing what it is. However, a standalone variable
>
> center
>
> probably does. What is it the centre of? An ellipse? Circle? Generic ROI?
>
> "Encapsulation" may be a bit of an OO buzzword, but even for procedural languages with structures it's an easy way to
> make code more readable and simple to maintain. That may not be an issue for a person or two writing code, but in a
> project where there are many people contributing (and in different timezones) it can be extremely helpful.
>
> And since IDL went OO, I think some of the conventional idioms can be tossed - particular those that are purely for
> procedural languages.
>
> FWIW, I'm dealing with the same issue in Fortran. Ever since it went OO with the Fortran2003 standard, I'm writing all
> new code with an OO bent. Makes home-grown "toolboxes" much easier to reuse.
>
> cheers,
>
> paulv
>
> p.s. And always always use Mike Galloy's unit testing framework too:http://mgunit.idldev.com/ :o)
Thanks for the input, everyone. I am glad to see support for a
structure, since that was my original preference. I like structures
and objects - even in an old-school language like IDL, I always find
my programs make more sense if I use them when possible.
The new OO syntax in 8.0 was a big improvement for me; along with the
hash table and list, this update has made IDL considerably more
pleasant.
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