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But you're missing the fact that you can exit a loop when you find what you need. You don't have to continue processing.
There are only 10 types of people in the world, those who understand binary and those who don't.
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What if you have two nested loops? It's a lot harder to exit them both...
The universe is composed of electrons, neutrons, protons and......morons. (ThePhantomUpvoter)
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Quote: What if you have two nested loops? You can't get out of the matrix.
I didn't say there was never a reason for returning from multiple places. I just said I prefer not to.
There are only 10 types of people in the world, those who understand binary and those who don't.
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Trust me, I took the red pill a loooong time ago!
The universe is composed of electrons, neutrons, protons and......morons. (ThePhantomUpvoter)
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There are only 10 types of people in the world, those who understand binary and those who don't.
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No. Actually it isn't. All you have to do (hush my mouth) is add a label to your single return point at the bottom of your procedure, and then (and I can't believe I'm saying this in open forum) "goto" that label. Simples!
Yes - I am more than old enough to know better but I do still use goto from time to time and I'm not totally averse to the odd setjmp/longjmp pair in my code.
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Or use a return, which is cleaner, and a lot more obvious...and won't get you strung up by the "goto is evil" lynch mob. And in this case it would be a horrible and unnecessary use of goto which would probably be deserving of the hempen necktie!
The universe is composed of electrons, neutrons, protons and......morons. (ThePhantomUpvoter)
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Yes, but MS recommends you install Windows 8 on your computer...
The universe is composed of electrons, neutrons, protons and......morons. (ThePhantomUpvoter)
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No no, it's Windows 8.1 now...
At least they're bright enough to realise 8 -> 8.1 should be a free upgrade.
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Easy: introduce a flag indicating when you're done processing (for whatever reason). You can either add that flag to the breaking condition of control statements, or add a single additional nesting layer inquiring the state of that flag everytime you're about to do some more processing (that could be skipped).
I've been using that concept successfully for a long time in legacy applications that have lots of very long functions with very high nesting levels. This method at most adds one nesting level, if at all, and it helps keeping track of stuff I need to clean up at various nesting levels before actually exiting the function.
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Yes you can, but...a return is a lot, lot cleaner!
The universe is composed of electrons, neutrons, protons and......morons. (ThePhantomUpvoter)
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... until you introduce code that needs clean-up at one point or another.
Many of the functions I look at every day are a decade old or more, and consist of several hundred lines of codes with half a dozen levels of nesting or more. Every single one of them allocates stuff, or does something else requiring cleanup. More often than not, this happens before something else happens that necessitates a premature return. Some of the really old functions use goto exit; to immediately jump to the cleanup code. I use a flag.
Sure, not everyone works on such a codebase. But the truth is, the majority of programmers doesn't work on brand-new projects either. 80% work on internal programs designed to improve certain processes inside of a single company. Lots of code, and sometimes with a lifetime higher than that of some of their current programmers. In that context, IME, premature returns are almost always a bad idea.
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Stefan_Lang wrote: Some of the really old functions use goto exit; to immediately jump to the cleanup code. I use a flag.
That's what try..finally is for. Both goto and flags fail miserably in the presence of exceptions.
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Why you think like that?
/* LIFE RUNS ON CODE */
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If we ever get around to refactor this, then maybe that is the way to go. But not anytime soon. When I said 'really old', I meant it: some of that code predates exception handling by a decade.
Besides, there are plenty of good reasons not to use exceptions at every possible opportunity. E. g. I suppose you wouldn't suggest the use of exceptions in the case of the OP
Flags (or states, if you prefer), are perfectly valid mechanisms for keeping track of the state of your processing. They're definitely not the only way to handle this, but there is no real downside to them either.
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Flags and/or gotos are both reasonable approaches in languages that don't have a try...finally construct and I've written code using both approaches in many different languages. Since the OP was obviously C# I assumed that is what we were talking about, and in C# the try..finally (or the "using" construct, when applicable) is definitely the cleanest approach to making sure your resource cleanup happens, even when you don't think exceptions enter into the picture, though in my experience most cases where resource cleanup happens, exceptions at the .NET framework level are almost always a possibility.
And no I wouldn't suggest try..finally for the original post because no resource cleanup is involved.
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Ok, lets forget language (old C) specific concerns: Assuming you have exceptions, yes, I agree that you can reasonably handle many cases of premature returns that way.
However, my take on exceptions is that code running as expected shouldn't throw one! Finding an element with specific properties in a container does not warrant throwing an exception, whether or not you need clean-up.
Look at the following code, ignoring language specific elements:
int find(Container c, double value, double tol)
{
int result = INVALID_ID; do_some_intialization();
for(size_t index = 0; index < c.size(); ++index)
{
if (element.distance(value) < tol)
{
result = element.ID();
}
}
do_some_clean_up();
return result;
}
There are various solutions to short-cut the loop once it finds a fitting element:
1. use some command that breaks out of the innermost loop (in C/C++ you can use break )
2. attach the check (result==INVALID_ID) to the loop header, so it quits once you assign a valid ID. (not sure how to do that with for_each in C#, but a standard for loop lets you add an arbitrary number of stop conditions easily)
3. Introduce a flag variable that indicates when you're done searching. As it would pretty much just store the current value of (result==INVALID_ID) in this case, you might as well go with solution 2 above
4. throwing an exception, catching it with try/finally to ensure proper cleaning up
In this example, my suggestion of introducing a flag variable turns out to be unneccesary, as the result variable itself can be used to pretty much the same effect. In my experience, this is often the case, so the effort to use these kind of checks instead of premature return s or goto s is often rather low.
Using an exception would certainly work, but it conflicts with my understanding of what an exception means. Also, if you do catch actual error cases with exceptions within that same code, you need to make sure to not catch the 'good-case-exceptions' as errors!
If you have no problem with that, the more power to you. But I prefer not to go that route.
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I think you've completely misunderstood what I said. I am in no way advocating introducing new exceptions as a way of prematurely ending a loop. What I am advocating is using language constructs (try...finally or using(...)) specifically designed help ensure safe cleanup regardless of how you exit the function/procedure. It's simply cleaner and easier to get it right than using other methods, especially when there is the possibility of exceptions, which it turns out is almost always when using resources that need to be explicitly cleaned up in languages that provide those constructs.
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Stefan_Lang wrote: premature returns are almost always a bad idea
Definitely a code smell.
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No, is not. This "one return only" style you talk about always produces uglier code, and is usually slower. This is clearly a personal style preference of yours and you are entitled to it, but if you think there is a general rule that recommends only one return then you should know you are wrong.
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throw an exception
To alcohol! The cause of, and solution to, all of life's problems - Homer Simpson
----
Our heads are round so our thoughts can change direction - Francis Picabia
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the 2 loops are a good example, but for me is easier to track multiple exit points than it is to track changes on a variable.
there may be a hundred variables involved, the return value can get reset, millions of things can happen, but when there's a return statement, i know it's over. whatever i've at that point is the result, i can track individual cases one at a time.
for me it's really easier to track execution paths this way, is it different for you?
the ammount of different opnions when we talk about code is just funny
opnions are the oposite of highlanders, there can never be only one.
I'm brazilian and english (well, human languages in general) aren't my best skill, so, sorry by my english. (if you want we can speak in C# or VB.Net =p)
"Given the chance I'd rather work smart than work hard." - PHS241
"'Sophisticated platform' typically means 'I have no idea how it works.'"
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Vague but true.
There are only 10 types of people in the world, those who understand binary and those who don't.
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