Encapsulation, inheritance and polymorphism

Steven D'Aprano steve+comp.lang.python at pearwood.info
Thu Jul 19 03:34:47 CEST 2012


On Wed, 18 Jul 2012 15:40:00 +0100, Lipska the Kat wrote:
[...]
>> Even with a break, why bother continuing through the body of the
>> function when you already have the result? When your calculation is
>> done, it's done, just return for goodness sake. You wouldn't write a
>> search that keeps going after you've found the value that you want, out
>> of some misplaced sense that you have to look at every value. Why write
>> code with unnecessary guard values and temporary variables out of a
>> misplaced sense that functions must only have one exit?
> 
> Object Oriented programming is all about encapsulating human concepts in
> a way that makes sense to human beings. Make no mistake, it is NEVER the
> case that a software system is written for any other reason than to
> serve human beings. OO is more than just the mechanics of writing code,
> it's a state of mind.

Um, yes?

I'm no sure what this has to do with single-exit functions/methods. You 
can just as easily write multi-exit methods in an OO language as in a non-
OO language. So long as your language has a return statement which exits 
the function, you can have more than one.

I am aware that some languages enforce a single exit point, but that 
seems to be an unnecessary restriction to me.

Of course it does require discipline and/or sense to not write crap code: 
if you have a 300 line function or method, whether it has dozens of exits 
or just one, that is crap code in any language. But if the choice is to 
write a 20 line function with three exits, or a 30 line function with a 
single exit, there would have to be a good reason to prefer the single-
exit version.


-- 
Steven



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