goto... Who uses it?
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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.
I am not afraid to say I used it at least 4 or 5 times! (in the last 10 years!...) Even once recently! I hate the mindless peer pressure against it, use it even it's ugly if you like! Use whatever makes your code more beautiful! ^^ Just so you know, the (mindless violent) hate against it is based on the following argument: "it's not maintainable" i.e. "it break the flow of the code which should be otherwise obvious" That much is true, long methods with goto label hidden 300 line below are big traps. But this is true of 300 lines method without goto too!!! So, shortly, use it if it's the shorter more expressive solution. If someone doesn't like it, suggest them to fix the code. And choose the most expressive readable code between theirs and yours after that! ;P Anyway, when one use goto? Err... truthfully only one C# exemple comes to my mind (apart switch): how to break out simple of multiple nest loop
for ()
for(..)
for(..)
{
if(condition)
goto exit_loop;
}
exit_loop:;Just so you know, a typical C goto will be for clean up, as in
if (success1) {...}
else goto failure
If (sucess2) { ...}
goto failure
...
return;
failure:but in C# this is more nicely expressed with
try {} catch {} finally {}which doesn't need any gotoMy programming get away... The Blog... DirectX for WinRT/C# since 2013! Taking over the world since 1371!
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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!
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I beg to differ here. Check out the IL generated for the two methods:
void Test()
{
while (true)
{
string str = "Something";if (str.Length != 10) { continue; } } } void Test2() { x: while (true) { string str = "Something"; if (str.Length != 10) { goto x; } } }//without GOTO .method private hidebysig instance void Test() cil managed { // Code size 32 (0x20) .maxstack 2 .locals init ([0] string str, [1] bool CS$4$0000) IL_0000: nop IL_0001: br.s IL_001c IL_0003: nop IL_0004: ldstr "Something" IL_0009: stloc.0 IL_000a: ldloc.0 IL_000b: callvirt instance int32 [mscorlib]System.String::get_Length() IL_0010: ldc.i4.s 10 IL_0012: ceq IL_0014: stloc.1 IL_0015: ldloc.1 IL_0016: brtrue.s IL_001b IL_0018: nop IL_0019: br.s IL_001c IL_001b: nop IL_001c: ldc.i4.1 IL_001d: stloc.1 IL_001e: br.s IL_0003 } // end of method Proof::Test //With GOTO .method private hidebysig instance void Test2() cil managed { // Code size 32 (0x20) .maxstack 2 .locals init ([0] string str, [1] bool CS$4$0000) IL_0000: nop IL_0001: br.s IL_001c IL_0003: nop IL_0004: ldstr "Something" IL_0009: stloc.0 IL_000a: ldloc.0 IL_000b: callvirt instance int32 [mscorlib]System.String::get_Length() IL_0010: ldc.i4.s 10 IL_0012: ceq IL_0014: stloc.1 IL_0015: ldloc.1 IL_0016: brtrue.s IL_001b IL_0018: nop IL_0019: br.s IL_0001 IL_001b: nop IL_001c: ldc.i4.1 IL_001d: stloc.1 IL_001e: br.s IL_0003 } // end of method Proof::Test2
"Bastards encourage idiots to use Oracle Forms, Web Forms, Access and a number of other dinky web publishing tolls.", Mycroft Holmes[^]
you're right, but bad example! ^^
void Test()
{
while (true)
{
string str = "Something";if (str.Length != 10) { continue; } blabla(); } } void Test2() { while (true) { string str = "Something"; if (str.Length != 10) { goto next; } blabla();next:;
}
}My programming get away... The Blog... DirectX for WinRT/C# since 2013! Taking over the world since 1371!
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Honestly, I have written at least 1 million lines of code since I have used a goto. Although I do remember using a few gotos in the 1990s. Also long gone from my coding is writing x86 assembly code.
John
In my early days I used them a lot - then I discovered methods and functions and stopped using them. The only exceptions are certain languages which require goto (e.g. VBScript/VBA error handling - on error goto 0). In studying computer science I was also told that there was one valid known use of a goto statement, which was in a washing machine with an 8 bit processor where the use of the goto statement allowed for a saving on hardware costs. Sadly I can't remember the detail / can't find more info online.
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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".
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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.
DanielSheets wrote:
It can make for cleaner code if used correctly.
Post an example then, or it isn't so. I see you did, in another sub-thread, see my response there for a cleaner equivalent.
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public static void SaveChartData(List dataList) { int totalDelays = 0; int value = 0; string errorString = ""; // Use a temporary file in case there are any parse errors. string tmpFilePath = applicationPath + "TmpChartData.csv"; using (StreamWriter sw = new StreamWriter(tmpFilePath)) { foreach (DataGridClass dgc in dataList) { if (!int.TryParse((dgc.MATL.Equals("") ? "0" : dgc.MATL), out value)) { errorString = dgc.MATL; goto ParseError; } totalDelays += value; if (!int.TryParse((dgc.EQUIP.Equals("") ? "0" : dgc.EQUIP), out value)) { errorString = dgc.EQUIP; goto ParseError; } totalDelays += value; if (!int.TryParse((dgc.People.Equals("") ? "0" : dgc.People), out value)) { errorString = dgc.People; goto ParseError; } totalDelays += value; if (!int.TryParse((dgc.Defects.Equals("") ? "0" : dgc.Defects), out value)) { errorString = dgc.Defects; goto ParseError; } totalDelays += value; if (!int.TryParse((dgc.Other.Equals("") ? "0" : dgc.Other), out value)) { errorString = dgc.Other; goto ParseError; } totalDelays += value; sw.WriteLine("{0},{1},{2},{3},{4},{5},{6},{7},{8},{9},{10}", dgc.Year, dgc.Month, dgc.Goal, dgc.Completions, totalDelays, dgc.to, dgc.MATL, dgc.EQUIP, dgc.People, dgc.Defects, dgc.Other); totalDelays = 0; value = 0; } } // If we got this far then there were no parse errors. File.Copy(tmpFilePath, chartData, true); return; ParseError: string msg = string.Format("Unable to parse data. Verify its entered correctly.\\r\\nValue = {0}", errorString); MessageBox.ShoQuite simple, break the foreach loop into a separate method, returning a boolean. Replace goto's with return. Improved structure, documents itself (call it ParseDataGridList(List<DataGrid> dataList) ) Caller simply uses "if" on return value - if true { copies file } else { show message } Fixed.
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Where do you see UI code in the snippet I posted?
DataGridClass
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Real programmers (ones who code in languages like assembly, C and FORTRAN) use it all the time. Rest of us - rarely if ever.
Nemanja Trifunovic wrote:
assembly, -C- and FORTRAN
FTFY - rarely used in C either. (Edit - C with strikethrough looked too much like a Euro symbol)
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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.
Interested in Machine Learning in .NET? Check the Accord.NET Framework. See also Haar-feature Object Detection (With The Viola-Jones Framework) in C#
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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.