on goto
in [ASM]
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From: Nick on 30 Apr 2010 14:41 "Daniel T." <daniel_t(a)earthlink.net> writes: > There is a general pattern here I think. When there are multiple exit > conditions to a loop (there is an && in the exit condition,) and we have > to be able to distinguish after the loop which condition caused it to > exit, then it may be appropriate to have multiple exits from the loop. > I'm just musing here, but what do you guys think? I'm very happy with it. My view is that leaving early is perfectly all right in at least two circumstances: a) in a "do I do this at all?" check at the start of some code b) when you've finished what you came to do (like finding something in a search function). For (a), I'd much rather see enum retval do_something(char *s) { if(s == NULL) return no_string; if(!*s) return empty_string; if(strlen(s) < 3) return short_string; while(*s) { if(....) } return not_found; } than something involving a pile of nested ifs and a variable to hold the eventual return value. This way you *know* that all's over with, without reading down to the bottom to check. -- Online waterways route planner | http://canalplan.eu Plan trips, see photos, check facilities | http://canalplan.org.uk
From: robin on 30 Apr 2010 20:59 "James Van Buskirk" <not_valid(a)comcast.net> wrote in message news:hr1q1g$h5v$1(a)news.eternal-september.org... | "Alexei A. Frounze" <alexfrunews(a)gmail.com> wrote in message | news:aab23e01-b4d4-44c4-a136-a619da00a3f7(a)m24g2000prc.googlegroups.com... | | > 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). | | Amusing that Fortran has a mechanism to break out of nested loops | and permits one to use internal subroutines for function cleanup, | not to mention no fall-through in SELECT CASE constructs. Thank goodness. | These uses | of goto are simply artifacts of the limitations of C-style languages.
From: James Kanze on 30 Apr 2010 21:31 On Apr 25, 12:17 pm, Phil Carmody <thefatphil_demun...(a)yahoo.co.uk> wrote: > James Kanze <james.ka...(a)gmail.com> writes: > > On Apr 24, 1:20 pm, "Leigh Johnston" <le...(a)i42.co.uk> wrote: > >> "spinoza1111" <spinoza1...(a)yahoo.com> wrote in message [...] > >> Because break only breaks out of the innermost loop, using > >> goto to break out of nested loops is one of the few sensible > >> uses of goto. > > But when do you have to break out of a nested loop? > For the same reason you want to break out of a single loop. > Do you have issues with people breaking out of single loops? I've never really seen a case where it was appropriate (if by "breaking out", you mean using the break statement to obfuscate the code by hiding the actual program flow). > > (And of course, the only valid use of break in C++ is to end > > a case in a switch. Otherwise, it's just a goto in > > disguise.) > What do you mean by 'otherwise' - even that's just a goto in > disguise? Yes, because switch is fairly broken. On the other hand, the language doesn't provide anything better. One of the most structured programs I ever saw was full of goto's. Because it was written in Fortran IV, and the language didn't provide any of the necessary structures natively. In the case of C/C++, about the only useful flow control structure that isn't provided natively is a true switch or case statement, so we have to use the one provided. -- James Kanze
From: Frank Kotler on 1 May 2010 02:36 io_x wrote: .... > -------------------- > yes "je .1" would it mean "if zero flag == 1 goto .1"; > "je" is a 'conditional' goto; > jmp is a goto. Whereas "break", in my world, is an "OS thing" and has to do with memory, not flow-control. I wanna use 'em both! Best, Frank
From: io_x on 1 May 2010 03:16
"Frank Kotler" ha scritto nel messaggio: > io_x wrote: > > ... >> -------------------- >> yes "je .1" would it mean "if zero flag == 1 goto .1"; >> "je" is a 'conditional' goto; >> jmp is a goto. > > Whereas "break", in my world, is an "OS thing" and has to do with memory, not > flow-control. I wanna use 'em both! yes i use in asm "je" and "jmp" [or their macro] both; but even "jmp .2" can be seen as a conditional goto too: "if 1 goto .2"? so Theorem: all gotos are 'conditional' gotos. i use "break" only in C/C++ because these language are understood in that way > Best, > Frank |