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It's true that break (and continue) are very similar to goto. However, it's also very restricted in scope, and it cannot jump backwards. It cannot jump into the midst of a loop either. That makes it less likely to accidentally break code.
I'm not saying it's good, but it's not quite as bad as goto can be.
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The good old goto debate. A goto is a bit like telling the computer that I don't want you to proceed to the next line of code, instead make some other line the next thing to execute. And we do that all the time: exit for, exit do, if some condition goto next line otherwise goto some other line. While some condition go into first line of loop block otherwise goto past the end of the loop block. And then, it all eventually becomes machine code / opcodes, and all of these become some kind of jump instruction, which is basically a goto. So for all you people out there that think that your code has no gotos, I can assure you the CPU is doing jump instructions left, right and centre as YOUR code runs in the CPU. Now please don't tell me that your code is somehow bypassing the CPU.
The reason this myth exists is that those early versions of BASIC had line numbers for each statement. And you would code "GOTO 760". Problem was when you inserted lines and made 760 line 761 or whatever but didn't go and update everything pointing to 760. And so this caused problems and bugs. Let's move on. We have alphabetic statement labels (used all the time in assembly language by the way), so you can now "Goto SomeLabelThatHasAMeaningfulNameThatWontBeRenumbered" and the problem is gone. Use goto freely, it's OK. I do it. It gets me out of deep nested rules and condition logic where I have established something I needed to establish. Yes there are always other ways to achieve the same result, but no - they are not always better or more elegant. And now it is time for me to go to bed.
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Umm, as you said goto caused problems if you used it and didn't really know how it worked. The thing is most (if not all) programs are compiled and this causes the assembler to move all the loops, functions anything else to the old loveable JMP or Jump statement (which is a go to this location). (Complains about "Softies not know how work things", burn hand on soldering iron!)
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The reason not to use goto is not a technical one, but a code cleanliness one. A goto is an unstructured jump and makes it much harder for a human brain to comprehend the structure of the procedure. Loops with breaks and continues, conditionals, switch blocks and so on may translate to jump instructions in assembler or IL, but they're structured and therefore easier to understand.
The only time I would say it might be okay is the 'double break' (i.e. breaking out of a 2D or deeper loop set). When your logic is this complex it's usually better to take the looping code out into a sub-procedure or -function and use return instead, because chances are that procedure is too long already. (You can always ask the compiler to inline it if you think the function stack is critical.) In modern languages, proper error condition handling (i.e. exceptions) have taken away most of the situations in which you'd want to do this.
So I agree up to a point: fundamentalist 'never' dictums (dicta?) are not particularly helpful. But it is very rarely the most elegant approach to use a goto.
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The most common argument I hear from experienced programmers is that a goto is a convenient way to jump around in an eight level nested loop.
This tells me they have mastered the function call yet.
But I can see how gotos can make it easier to navigate spaghetti code.
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The point I was making was: use Goto when it is good to do so. That's a matter of judgement. It probably won't be often. But use it freely when you consider that it works well - when it simplifies or clarifies the logic flow. Don't be religious about following some rule that you heard somewhere. "Shoulds", "don'ts" and "nevers" are a poor substitute for judgement.
The fool knows the answer, the wise man thinks.
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This is a simplistic example of the sort of thing I am talking about. My sympathies to those of you who find it un-structured, hard to understand, un-clean or bad code. Let me see yours.
if WageEarner then
WeeklyPay = HrsWorked * Rate
Goto WklyPayDetermined
end if
if SalaryEearner then
WeeklyPay = (Salary * 7) / 365
Goto WklyPayDetermined
end if
if FutureHire then
WeeklyPay = 0
Goto WklyPayDetermined
end if
if Retired then
if WasWageEarner then
WeeklyPay = FinalRate * 40 * 0.5
Goto WklyPayDetermined
else
WeeklyPay = 0.6 * (Salary * 7) / 365
Goto WklyPayDetermined
end if
end if
WklyPayDetermined:
TaxDeductible = WorkOutTax(WeeklyPay)
CreateBankTransaction(WeeklyPay - TaxDeductible)
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I've seen justifiable GOTOs in C code. Usually, the scenario involves nested control structures (IFs or loops) and the possibility of a trash-it-all error deep in the nest. C++ offers less of an excuse for GOTOs, because of the ease of use of the exception mechanism.
That having been said, if a programmer feels he can defend his use of a GOTO, and his program is otherwise legible and maintainable, it's usually not worth starting an RWAR over it. That is, unless you enjoy RWARs for their own sake!
(This message is programming you in ways you cannot detect. Be afraid.)
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andrewgissing wrote: Msny years ago
Years before MSN, you mean? 
-= Reelix =-
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The gosub call was the mechanism for calling faux functions / subroutines.
Unlike the goto, the last address was pushed on the stack so the subroutine could return to the location it was called from.
They were a big improvement over goto.
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You should try to rewrite that code with goto statements instead of gosub, and see what you get. 
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Gosubs were used alot in the old days when programming in GWbasic and basica. think the time I used them was in dos 2.11
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Is it better to have a ridiculous number of nested levels of "if" statements? Sometimes the inability of having a goto results in a lengthy "elegant" work-around to avoid nesting purgatory.
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That sounds like a false choice to me.
Do you often find yourself programming a ridiculous number of nested if statements?
I often encounter situations with a lengthy series of if statements. But for those, you execute a short code block and return.
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The original point of limiting goto's was lost almost immediately in COBOL where a goto out of a paragraph that was performed would result in a stack overflow or the more harder to debug no-longer-valid stack entry. This type of goto was discouraged for the proper reasons, namely that the program would fail completely or fail to work properly when mixing performs and goto's in this manner.
In the effort to promote 'structured programming', this message morphed into "no goto's". This was a much simplified version and promotes code reuseability, although it eliminates the very useful goto beginning-of-paragraph and goto exit-paragraph statements.
This 'simplify the message' has carried over to every programming language ever since.
Too bad.
Charlie
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Haters being haters again. Sigh. A little historical context might be helpful here.
If you never programmed in a circa 1980 BASIC, the language did not provide named subroutines or structured control statements, symbolic labels or indentation. GOTO was all you had. To complain about GOTO in a language that has nothing else is just hating. This code implemented a very structured thing, a finite state machine. It was actually best practice for this language that the states were in subroutines and the GOSUBs in the main loop were all together.
Back in the 1960's when many of your moms and dads were children, W Edsgar Dijkstra penned his fameous "GOTO Considered Harmful" article, and Ed Yourdon and others kicked off the "Structured Programming" movement, with its emphasis on single-entry/single-exit programming. (The structured programming movement was a good idea, but it had the same high hype-to-value ratio as Agile does today.) Languages of the day, led by PASCAL, went a little too far, requiring for instance that all functions return out the bottom, so that you often had to use a bit of state to guard if and while statements (WHILE NOT DONE AND ...) so execution would flow down the page and out the end of the function.
People used this as evidence that we did so need GOTO. Then C came along with its break, continue, and return statements and relaxed the rules a bit. There were arguments from the SP folks that these statements were a bad thing, but practitioners won the day.
There were GOTOs to exit code that returned resources. These, said GOTO fans, were evidence that GOTO was unavoidable. This was mostly hogwash, as you could test most resources to see if they'd been allocated, and only return the ones that were. And the arrival of exception handling and the resource-allocation-is-initialization idiom in C++ rendered that discussion moot.
GOTO has few places left to hide. I haven't needed to use a GOTO since 1995, and I have cleaned up many a function by removing GOTOs and fixing up the logic to make it simpler and more correct. I would not miss GOTO if it were removed from C++. It's only there (like many C++ features) for compatibility with old and poorly written C programs.
[pours gasoline on the fire]
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Why use all of those ifs? There is an 'on gosub' statement in a lot of BASIC implementations.
Yep, it sure is a horror.
Just because goto would be better in this instance does not make goto any less of a horror in my opinion.
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My signature line says it all.
If you think 'goto' is evil, try writing an Assembly program without JMP.
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If I'm not sure will compiler will understand goto's replacement better, I prefer goto (never trust any compiler).
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Anyone who has been around for a long time may remember that the GOTO-less programming controversy was laid to rest (in FORTRAN anyway) by an article published in the December 1973 issue of Datamation magazine. I kept a copy of that article all these years in my humour file as it proposed solving the problem by eliminating GOTO statements entirely and replacing them with the COME FROM statement. Here is an excerpt from the article entitled "A Linguistic Contribution to GOTO-less Programming" (Thanks to the miracle of the internet, the full article can now be found online at this link: http://www.fortran.com/come_from.html )
---------------------------------------------------------
"This statement causes control to be
transferred to the next statement (the
statement immediately following the
COME FROM) upon completion of the
designated statement.
Example:
10 J = 1
11 COME FROM 20
12 WRITE (6,40) J
STOP
13 COME FROM 10
20 J = J+2
40 FORMAT (I4)
Explanation:
In this example, J is set to I by state-
ment 10. Statement 13 then causes control to
be passed to statement 20, which sets J to 3.
Statement 11 then causes control to be passed
to statement 12, which writes the current value
of J. The STOP statement then terminates the
program."
----------------------------------------------
In all seriousness, I have not had to use a goto statement in all the code I have written since the day that structured FORTRAN replaced FORTRAN IV on our mainframes in the early 80's. And I am including all the languages I have since used up until today: C, C++, PL/1, Java, C#, VB, Lisp, APL, and JavaScript. It is almost always possible to refactor logic that appears to require a goto into an equivalent form that doesn't. If your nesting is too deep, refactor into shorter, more succinct, and readable methods. Modern IDE's make refactoring dead easy and I have made extensive use of refactoring support in Eclipse as well as Visual Studio.
But for any fans of computer history, do yourself a favour and read the entire article at the link above.
Apologies for the Canadian (ie. British) spelling of 'humour' and 'favour'. I know they are somewhat anachronistic today, but that was how I was taught.
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Ok, I lied...I just checked some of my FORTRAN source code written in 1985 and there were a handful of goto statements in 20,000 lines of code. But since FORTRAN, I have not used goto's (to the best of my knowledge 
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Use a real language
Just as a reminder BASIC = BEGINNERS All Purpose Instruction Code
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... stuff like this:
switch (Session["Benutzer_Firma"].ToString())
{
case "ABC":
lblManipulation.Text = "Some text in a label";
break;
case "DEF":
lblManipulation.Text = "Some other text in a label";
break;
case "Default":
lblManipulation.Text = "The default text for the label";
break;
default:
goto case "Default";
break;
}
I just found this in a 9000 line ASP.Net page and the rest of it is not a bit better than this. The only things I have changed are the literal strings because the company was mentioned there several times. Especially the lines with the switch statement and the default case are inspiring.
And am I too harsh if I want to have the 'developer' thrown out of the guild, tarred, feathered and then chased out of the city?
I'm invincible, I can't be vinced
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CDP1802 wrote: And am I too harsh if I want to have the 'developer' thrown out of the guild, tarred, feathered and then chased out of the city?
You missed the troll kick to the nadgers.
Panic, Chaos, Destruction. My work here is done.
Drink. Get drunk. Fall over - P O'H
OK, I will win to day or my name isn't Ethel Crudacre! - DD Ethel Crudacre
I cannot live by bread alone. Bacon and ketchup are needed as well. - Trollslayer
Have a bit more patience with newbies. Of course some of them act dumb - they're often *students*, for heaven's sake - Terry Pratchett
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