goto... Who uses it?
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dusty_dex wrote:
Many a word has been written about the use of multiple exits being bad practice.
I think I understand the issue from all sides and I don't drink that kool-aid. The way I look at it, the goto takes linear flow and folds it back on itself, causing the programmer to think about an interleaved mesh of logic instead of a stream. I see the following items as presenting different concepts and approve/disapprove of each on their own merits: (1) goto backwards within a loop (2) goto forwards within a loop (3) goto forwards to exit handler/error handler at end of method (4) break statement in a loop (4a) bounded loop (4b) infinite loop (ie. exit in the middle) (5) break statement in a switch() (6) continue statement in a loop (7) return statement inside a loop (one only per method) (8) multiple return statements in a method History has shown that #1 has caused the most problems, and #2 follows closely. #3 seems to be the one that most people defend, and I think it has some merit. I have used #3 but I still avoid it whenever I can. I regularly use all of #4 through #8 and have no problem with them. Multiple returns in a method are really no different from a break statement in terms of how the programmer's brain processes the logic. Multiple returns cause an exit from a method (so there is no tortured logic flow), you can debug it (eg. you can put a breakpoint on it), do not fold logic back (so that you can get to a statement from multiple directions) and can reduce the amount of code in a method (less code is better code). Probably other things too - this is off the top of my head.
-- Harvey
H.Brydon wrote:
causing the programmer to think about an interleaved mesh of logic instead of a stream
It also means that an optimiser is severely limited in the transformations it can make to code while retaining correctness - so will generally have a direct impact on performance too.
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I hate all those anti-goto people! :mad:
My programming get away... The Blog... DirectX for WinRT/C# since 2013! Taking over the world since 1371!
That's OK, you're welcome to Goto Hell! ;-)
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None dare mention the fact that "break" and "goto" are really the same thing
No they are not. Break is designed to allow breaking out of a construct in a predictable, limited way. OK, in generated code, the result is still a branch, but one is much less likely to lead to abuses of control flow, particularly with later maintenance.
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This isn't a programming question. Anyway... I find it useful in very few situations. It can make for cleaner code if used correctly. Of course, it can also be over used.
The goto is not required, you can always skip around with variable but sometime it's the best solution. In this example the goto is a clear simple example, remove it and you introduce less readable and more complexity.
function BigFunction() {
for (int i =0; i < 100; i++) {
while(true) {
if (...) {
goto DO_SOMETHING_AT_THE_END;
}
}
}DO_SOMETHING_AT_THE_END:
DoSomething();
} -
Collin Jasnoch wrote:
There is no "correct" usage of it in modern high level languages
I doubt the the absoluteness of that statement. It is likely there are few cases but even one refutes your statement.
"correct use" depends on your definition of "correct". However, the main point is that even if at first it makes sense, or even simplifies code, it suffers from the lack of long-tem maintainability: Unlike other control statements, goto lacks an associated block of control, and thus makes it considerably harder to detect or verify the effect of any change you make to code that may or may not be executed, once or repeatedly, depending on goto statements in potentially several entirely different place(s). Goto would be much less of a problem if jump labels weren't self-declaring and global: if you could localize the use of a label like variable names, that would greatly restrict the potential (ab)use of goto commands, and thus ease the effort to understand the code and verify changes.
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I would one step further since the ternary test is not only silly, it might throw an exception all on it's own due to text being null. If you KNOW something is "0", why parse it to 0? Why is an empty string valid? Is a null string valid? The code has other problems. Why create the file before you know whether there are any errors? Why set totalDelays and value back to zero? "its" is spelled "it's" in this context, but it should probably read "it was".
Joe Woodbury wrote:
I would one step further since the ternary test is not only silly, it might throw an exception all on it's own due to text being null. If you KNOW something is "0", why parse it to 0? Why is an empty string valid? Is a null string valid?
I dont know its going to be zero. It could be any number and it will never be null. An empty string is valid because a previous version of this code used them. This version doesnt.
Joe Woodbury wrote:
The code has other problems. Why create the file before you know whether there are any errors?
Because there are terminals that watch for changes in this file. If a parse fails then I have a partially written data file. This will cause several other terminals to report errors.
Joe Woodbury wrote:
Why set totalDelays and value back to zero?
Because totalDelays is for each individual class in dataList. If it's not set back to zero then it will add up across all of the classes in the list. You're making assumptions here. Setting delays to zero is unnecessary. That was left over and can be removed.
Joe Woodbury wrote:
"its" is spelled "it's" in this context, but it should probably read "it was".
Thanks for pointing that out. That grammatical error could cause the entire app to crash and burn. Good catch.
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This isn't a programming question. Anyway... I find it useful in very few situations. It can make for cleaner code if used correctly. Of course, it can also be over used.
It is often considered OK to call a goto from a deeply nested loop in order to terminate all loops altogether early, without the need of adding and maintaining several guard variables in the loop conditions. Of course if you can afford to place your loop in a separate function, you can also return from that, eliminating the goto but still doing the same.
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If we are talking of C# then I cant think of a time I would ever use it , although I am somewhat biased as I have told everyone in my team that I would slaughter a family member if I ever found it in any code .
Who would put family members in their code? :wtf:
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This isn't a programming question. Anyway... I find it useful in very few situations. It can make for cleaner code if used correctly. Of course, it can also be over used.
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His second stop was the bar, then other places and to write this post. I am assuming he is still enjoying the effects of the local bar. :)
Common sense is admitting there is cause and effect and that you can exert some control over what you understand.
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The goto is not required, you can always skip around with variable but sometime it's the best solution. In this example the goto is a clear simple example, remove it and you introduce less readable and more complexity.
function BigFunction() {
for (int i =0; i < 100; i++) {
while(true) {
if (...) {
goto DO_SOMETHING_AT_THE_END;
}
}
}DO_SOMETHING_AT_THE_END:
DoSomething();
}I think this example is pretty much the only justfiable use these days. I'm not ashamed to say that I use it this way occassionally. I much prefer that to deep nesting and multiple function returns. Multiple function returns often introduce bugs that could be avoided by using goto. But I'm wary of the religious wars against using goto so when I do use it I make sure I could justifty it in a code review.
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Been writing code since '85. Never used a goto in production code and I would have serious issue[s] with anyone who did.
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Been writing code since '85. Never used a goto in production code and I would have serious issue[s] with anyone who did.
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This isn't a programming question. Anyway... I find it useful in very few situations. It can make for cleaner code if used correctly. Of course, it can also be over used.
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This isn't a programming question. Anyway... I find it useful in very few situations. It can make for cleaner code if used correctly. Of course, it can also be over used.
GOTO is a vital tool for programmers wanting to develop high performance applications. In my primary commercial product (a GUI engine used by other programmers) I use it over a dozen times. Even the likes of Alexander Stepanov consider it useful, so I am in good company.
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This isn't a programming question. Anyway... I find it useful in very few situations. It can make for cleaner code if used correctly. Of course, it can also be over used.
Its been beaten into me over the years not to use GOTO's. Programming languages differ, but most have some sort of if / then / else that makes clearer programming than goto. Loops with leave / break statements, etc.. Even Fortran has these (I used it before it did)... I find indenting with GOTO replacements clearer to follow than hunting for GOTO's and their destination. Esp if you have huge functions. Even DOS batch scripting has if / then statements. Few years ago I cleaned up some messy batch scripts to make them readable...
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No they are not. Break is designed to allow breaking out of a construct in a predictable, limited way. OK, in generated code, the result is still a branch, but one is much less likely to lead to abuses of control flow, particularly with later maintenance.
Point well taken. The misuse of Branches (or Jumps or whatever a given syntax may use) is probably one of the factors that led to the abandonment of assembly language; my true love. ICEs with a good 32 instruction backward trace capability will almost always provide the debug needed. But that's a moot point these days. The "consensus" has decreed, and so I (and thousands of others) suffer. Sad.
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That ternary cannot throw. You're thinking of Java and its .equals nonsense. == won't throw for a null.
Learned something new.