on goto
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From: Juha Nieminen on 25 Apr 2010 01:09 In comp.lang.c++ Ali Karaali <alicpp(a)gmail.com> wrote: > I use goto to break nested for loops and I can't see a > reason to ban goto. No. The correct keyword for breaking out of nested loops (in C++) is 'return'. If you are using 'goto' for that purpose, you are doing it wrong. "It's not the same thing". Precisely. If you design your code such that you can always use 'return' to break out of nested loops, it will become cleaner and easier to understand. I have been programming in C++ both professionally and as a hobby for over 10 years, and I have never got into a situation where 'goto' would have been a tempting alternative because of being a simpler and more straightforward solution than something else. It just doesn't come up. I don't remember ever having written a 'goto' in the last 10+ years. It's not a question of banning 'goto'. There is no *need* for 'goto'. And if you code in such way that you just don't need it, your code will become cleaner in a completely natural way.
From: Alexei A. Frounze on 25 Apr 2010 03:46 On Apr 24, 3:33 pm, James Kanze <james.ka...(a)gmail.com> wrote: > On Apr 24, 10:26 pm, Phil Carmody <thefatphil_demun...(a)yahoo.co.uk> > wrote: > > > Tim Streater <timstrea...(a)waitrose.com> writes: > > > I haven't used a goto since 1978 (when I stopped writing > > > FORTRAN). > > Me neither. > > > I'm with Knuth. > > In other words, if goto makes the code simpler, it means that > you haven't found the correct expression of the algorithm. > > And of course, the problem isn't with goto, per se. It's with > the way it is used. But because it can be abused so badly, > modern languages (including C and C++) provide all of the > necessary structures (and then some) so you don't have to use > it. I wish there were distinct breaks for loops and switches as well as multi-level breaks for nested loops. goto's at times are the least evil since they don't require you to implement extra variables to break out of nested loops and they help to simplify function cleanup code (where resources are being freed on various conditions). > > I've reviewed patches and told the submitter to just convert > > all his jumble of 'structure' into nice clean goto statements > > many times this year. I don't use it for my own code, but > > $DAYJOB has a clear coding style that recommends goto in many > > situations. If goto has made your function unreadable, it was > > probably too big and unreadable anyway. > > If goto seems necessary, it's because your function is too big > and unreadable. But you don't want too many trivial functions either for you won't see the forest behind the trees. There should be a certain balance, subjective, of course, but it's not like goto's are evil no matter what. If they are evil, let's remember about pointers, which require a lot of care. And about horrible type conversions, where you can't even safely compare a signed int and an unsigned int (which is an absurd thing, IMO). And then about non-portable things, about implementation- defined/specific and undefined behavior. Now we're talking. goto is just nothing compared to all of that. :) Alex
From: Alexei A. Frounze on 25 Apr 2010 04:07 On Apr 24, 10:09 pm, Juha Nieminen <nos...(a)thanks.invalid> wrote: > In comp.lang.c++ Ali Karaali <ali...(a)gmail.com> wrote: > > > I use goto to break nested for loops and I can't see a > > reason to ban goto. > > No. The correct keyword for breaking out of nested loops (in C++) is > 'return'. If you are using 'goto' for that purpose, you are doing it > wrong. Now, let's consider C (or C++ where this function has to explicitly free up some used resources or do some other cleanup). The objects won't get freed here automatically by the magic of the destructor call generated for you by the C++ compiler. You could implement the cleanup code in several places of that function as block operators ending with a return, but very often these blocks are to a certain degree duplicates of one another. And it's not just the source code bloat that's bad, it's also us making a trap for ourselves because one day we may modify the function and forget to modify one or more of these cleanup block operators in it. > "It's not the same thing". Precisely. If you design your code such that > you can always use 'return' to break out of nested loops, it will become > cleaner and easier to understand. > > I have been programming in C++ both professionally and as a hobby for > over 10 years, and I have never got into a situation where 'goto' would > have been a tempting alternative because of being a simpler and more > straightforward solution than something else. It just doesn't come up. > I don't remember ever having written a 'goto' in the last 10+ years. > > It's not a question of banning 'goto'. There is no *need* for 'goto'. > And if you code in such way that you just don't need it, your code will > become cleaner in a completely natural way. Surprisingly, my code is pretty clean with gotos, which, btw, I use just for almost exclusively 2 things: - breaking out of nested loops (not always, if I can do that w/o writing more than two lines of code, I don't use goto) - jumping to the common cleanup code at the end of the function when I detect some error I get by without goto in almost all other situations. I don't see what's not natural here. It's a clearly written and structured code, that is easy to follow, without surprises, without bloat. Of course, if you never need to do any cleanup or you never check error conditions or rely heavily on C++ exceptions, the 2nd use may be just unnatural to you as it is to me since I'm programming C, mixed C and C+ + and I often have to deal explicitly with resource allocation. Alex
From: spinoza1111 on 25 Apr 2010 04:09 On Apr 25, 1:09 pm, Juha Nieminen <nos...(a)thanks.invalid> wrote: > In comp.lang.c++ Ali Karaali <ali...(a)gmail.com> wrote: > > > I use goto to break nested for loops and I can't see a > > reason to ban goto. > > No. The correct keyword for breaking out of nested loops (in C++) is > 'return'. If you are using 'goto' for that purpose, you are doing it > wrong. Don't you mean "break"? Return exits the containing function and has its place, certainly, under abnormal conditions. But break goes to the statement following the loop and is considered acceptably structured in reality, because it can be so readily simulated as I've shown using a flag. > > "It's not the same thing". Precisely. If you design your code such that > you can always use 'return' to break out of nested loops, it will become > cleaner and easier to understand. > > I have been programming in C++ both professionally and as a hobby for > over 10 years, and I have never got into a situation where 'goto' would > have been a tempting alternative because of being a simpler and more > straightforward solution than something else. It just doesn't come up. > I don't remember ever having written a 'goto' in the last 10+ years. > > It's not a question of banning 'goto'. There is no *need* for 'goto'. > And if you code in such way that you just don't need it, your code will > become cleaner in a completely natural way.
From: io_x on 25 Apr 2010 04:31
"Rod Pemberton" ha scritto nel messaggio > "io_x" <a(a)b.c.invalid> wrote in message > Structured programming generally requires a single entry and single exit > from any procedure or loop. it should be for one loop one single entry but one or more exits [at last for error code "more exits"] > It seems you stirred up the comp.lang.c, comp.lang.c++, crowds... I've > removed them from this post. I'm not interested in hearing from them that > my experience and knowledge is wrong. they not understand that all with goto is easy, easier than their difficult way of describe one algorithm, and more flexible |