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Groups > comp.lang.c > #157009
| From | Tim Rentsch <tr.17687@z991.linuxsc.com> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: Effective uses of c `goto' statement |
| Date | 2020-12-06 18:43 -0800 |
| Organization | A noiseless patient Spider |
| Message-ID | <86zh2qibea.fsf@linuxsc.com> (permalink) |
| References | (2 earlier) <20201202120809.633@kylheku.com> <86sg8kkyjb.fsf@linuxsc.com> <_CPyH.64249$7D7.63135@fx03.iad> <86ft4jkry3.fsf@linuxsc.com> <ml5zH.56199$hg2.7498@fx20.iad> |
Richard Damon <Richard@Damon-Family.org> writes:
> On 12/6/20 8:03 AM, Tim Rentsch wrote:
>
>> Richard Damon <Richard@Damon-Family.org> writes:
>>
>>> On 12/5/20 11:28 AM, Tim Rentsch wrote:
>>>
>>>> Kaz Kylheku <563-365-8930@kylheku.com> writes:
>>>>
>>>> [...]
>>>>
>>>>> Finite automata re easily implemented without goto, but only goto
>>>>> offers the most efficient possible representation with the fewest
>>>>> state variables (possibly with no state variable at all).
>>>>
>>>> Unless you can offer some sort of argument supporting this
>>>> assertion, I'm inclined to believe it is not the case.
>>>
>>> Well, you can build the Finite automata where the state you are in
>>> is the last label you did a 'goto' to (with an optimization that if
>>> it is the next lable, the goto can be implied). That basically
>>> eliminates the state variable (maybe some state works better in a
>>> state variable if you have a series of states that are similar and
>>> just use a counter).
>>
>> Yes, I understood that already.
>>
>>> The non-goto method is typically a switch statement based on the
>>> state variable, all in a while loop. There each state changes the
>>> variable and breaks from the switch, and then loops in the while to
>>> go to the next state.
>>
>> A common way to implement a state machine is with a switch()
>> inside a loop of some sort (e.g., for() or while()). I got that
>> already also.
>>
>> My question is about other possibilities that do not use goto
>> but also do not use state variables.
>
> I think the key is that the state needs to be stored somehow. It
> can be explicitly in a variable, or implicitly in the processor
> address, but it needs to be somewhere.
Yes, no doubt about that.
> It could perhaps be also done in functions that return the address
> of the function that is the next state, and that address is directly
> called and not saved so no 'state variable' every really existed.
Not in its usual sense, for sure. Written in a simple way, we
might see something like this:
SomeSortOfFunction f = ...;
while( f ) f = f( &fsm_data );
> The tricky part here is that in C you can not define a function of
> the self-referenctial type of a function that returns a pointer to a
> function of its type, so it needs to return a different type of
> function pointer that is casts to its type and then called.
We can't define a type in C that is directly recursive, but we
can achieve a similar effect using structs and pointers:
struct function_returning_itself_s;
typedef struct function_returning_itself_s *FtoF;
typedef struct function_returning_itself_s {
FtoF (*it)( long * );
} FtoF_object[1];
FtoF
wits_end( long *data ){
static FtoF_object me = {{ wits_end }};
if( !data ) return 0;
return me;
}
void
run_fsm( FtoF f, long *data ){
while( f ) f = f->it( data );
}
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Effective uses of c `goto' statement kevin shell <kevin@fedora.osfans.org> - 2020-12-02 16:42 +0800
Re: Effective uses of c `goto' statement Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-12-02 01:07 -0800
Re: Effective uses of c `goto' statement Anton Shepelev <anton.txt@gmail.com> - 2020-12-02 20:18 +0300
Re: Effective uses of c `goto' statement Anton Shepelev <anton.txt@gmail.com> - 2020-12-02 20:56 +0300
Re: Effective uses of c `goto' statement David Brown <david.brown@hesbynett.no> - 2020-12-02 19:30 +0100
Re: Effective uses of c `goto' statement Kaz Kylheku <563-365-8930@kylheku.com> - 2020-12-02 19:35 +0000
Re: Effective uses of c `goto' statement David Brown <david.brown@hesbynett.no> - 2020-12-02 21:05 +0100
Re: Effective uses of c `goto' statement Vir Campestris <vir.campestris@invalid.invalid> - 2020-12-02 18:07 +0000
Re: Effective uses of c `goto' statement David Brown <david.brown@hesbynett.no> - 2020-12-02 19:33 +0100
Re: Effective uses of c `goto' statement Siri Cruise <chine.bleu@yahoo.com> - 2020-12-02 10:22 -0800
Re: Effective uses of c `goto' statement Kaz Kylheku <563-365-8930@kylheku.com> - 2020-12-02 20:18 +0000
Re: Effective uses of c `goto' statement David Brown <david.brown@hesbynett.no> - 2020-12-02 23:16 +0100
Re: Effective uses of c `goto' statement Kaz Kylheku <563-365-8930@kylheku.com> - 2020-12-03 01:31 +0000
Re: Effective uses of c `goto' statement David Brown <david.brown@hesbynett.no> - 2020-12-03 08:39 +0100
Re: Effective uses of c `goto' statement Siri Cruise <chine.bleu@yahoo.com> - 2020-12-02 23:48 -0800
Re: Effective uses of c `goto' statement Kaz Kylheku <563-365-8930@kylheku.com> - 2020-12-03 17:49 +0000
Re: Effective uses of c `goto' statement Bonita Montero <Bonita.Montero@gmail.com> - 2020-12-03 17:09 +0100
Re: Effective uses of c `goto' statement Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-12-05 08:28 -0800
Re: Effective uses of c `goto' statement Richard Damon <Richard@Damon-Family.org> - 2020-12-05 12:41 -0500
Re: Effective uses of c `goto' statement Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-12-06 05:03 -0800
Re: Effective uses of c `goto' statement Richard Damon <Richard@Damon-Family.org> - 2020-12-06 08:51 -0500
Re: Effective uses of c `goto' statement Richard Damon <Richard@Damon-Family.org> - 2020-12-06 08:56 -0500
Re: Effective uses of c `goto' statement Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-12-06 18:43 -0800
Re: Effective uses of c `goto' statement Öö Tiib <ootiib@hot.ee> - 2020-12-06 05:58 -0800
Re: Effective uses of c `goto' statement Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-12-06 16:54 -0800
Re: Effective uses of c `goto' statement Siri Cruise <chine.bleu@yahoo.com> - 2020-12-05 10:01 -0800
Re: Effective uses of c `goto' statement Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-12-06 04:55 -0800
Re: Effective uses of c `goto' statement Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-12-03 21:20 -0800
Re: Effective uses of c `goto' statement Siri Cruise <chine.bleu@yahoo.com> - 2020-12-03 21:50 -0800
Re: Effective uses of c `goto' statement Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-12-03 23:06 -0800
Re: Effective uses of c `goto' statement Siri Cruise <chine.bleu@yahoo.com> - 2020-12-04 00:27 -0800
Re: Effective uses of c `goto' statement foo <opaquefoo@gmail.com> - 2020-12-02 11:03 -0800
Re: Effective uses of c `goto' statement David Brown <david.brown@hesbynett.no> - 2020-12-02 21:02 +0100
Re: Effective uses of c `goto' statement Öö Tiib <ootiib@hot.ee> - 2020-12-05 03:04 -0800
Re: Effective uses of c `goto' statement Öö Tiib <ootiib@hot.ee> - 2020-12-05 03:36 -0800
Good thing this isn't a Python group (Was: Effective uses of c `goto' statement) gazelle@shell.xmission.com (Kenny McCormack) - 2020-12-05 11:45 +0000
Re: Good thing this isn't a Python group (Was: Effective uses of c `goto' statement) David Brown <david.brown@hesbynett.no> - 2020-12-05 14:38 +0100
Re: Good thing this isn't a Python group (Was: Effective uses of c `goto' statement) Jorgen Grahn <grahn+nntp@snipabacken.se> - 2020-12-06 11:00 +0000
Re: Good thing this isn't a Python group (Was: Effective uses of c `goto' statement) gazelle@shell.xmission.com (Kenny McCormack) - 2020-12-06 12:33 +0000
Re: Good thing this isn't a Python group Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-12-06 14:09 -0800
Re: Good thing this isn't a Python group Jorgen Grahn <grahn+nntp@snipabacken.se> - 2020-12-08 21:01 +0000
Re: Effective uses of c `goto' statement David Brown <david.brown@hesbynett.no> - 2020-12-05 14:37 +0100
Re: Effective uses of c `goto' statement Kaz Kylheku <563-365-8930@kylheku.com> - 2020-12-02 20:07 +0000
Re: Effective uses of c `goto' statement Bonita Montero <Bonita.Montero@gmail.com> - 2020-12-03 17:10 +0100
Re: Effective uses of c `goto' statement "jfbod...@gmail.com" <jfbode1029@gmail.com> - 2020-12-03 15:40 -0800
Re: Effective uses of c `goto' statement Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-12-03 16:14 -0800
Re: Effective uses of c `goto' statement kevin shell <kevin@fedora.osfans.org> - 2020-12-04 16:29 +0800
Re: Effective uses of c `goto' statement "jfbod...@gmail.com" <jfbode1029@gmail.com> - 2020-12-04 07:09 -0800
Re: Effective uses of c `goto' statement "james...@alumni.caltech.edu" <jameskuyper@alumni.caltech.edu> - 2020-12-04 10:14 -0800
Re: Effective uses of c `goto' statement Bart <bc@freeuk.com> - 2020-12-04 11:19 +0000
Re: Effective uses of c `goto' statement Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-12-04 04:35 -0800
Re: Effective uses of c `goto' statement Bart <bc@freeuk.com> - 2020-12-04 13:50 +0000
Re: Effective uses of c `goto' statement Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-12-04 10:49 -0800
Re: Effective uses of c `goto' statement Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-12-04 13:09 +0000
Re: Effective uses of c `goto' statement Bart <bc@freeuk.com> - 2020-12-04 14:03 +0000
Re: Effective uses of c `goto' statement Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-12-03 23:02 -0800
Re: Effective uses of c `goto' statement Bonita Montero <Bonita.Montero@gmail.com> - 2020-12-04 19:38 +0100
Re: Effective uses of c `goto' statement Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-12-05 01:29 -0800
Re: Effective uses of c `goto' statement kegs@provalid.com (Kent Dickey) - 2020-12-09 00:23 -0600
Re: Effective uses of c `goto' statement Bart <bc@freeuk.com> - 2020-12-09 12:39 +0000
Re: Effective uses of c `goto' statement Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-12-10 10:45 -0800
Re: Effective uses of c `goto' statement Bonita Montero <Bonita.Montero@gmail.com> - 2020-12-04 19:35 +0100
Re: Effective uses of c `goto' statement Richard Damon <Richard@Damon-Family.org> - 2020-12-04 19:49 -0500
Re: Effective uses of c `goto' statement Richard Damon <Richard@Damon-Family.org> - 2020-12-04 20:52 -0500
Re: Effective uses of c `goto' statement Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-12-05 02:19 +0000
Re: Effective uses of c `goto' statement Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-12-05 01:43 -0800
Re: Effective uses of c `goto' statement "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2020-12-05 02:00 -0800
Re: Effective uses of c `goto' statement "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2020-12-05 02:01 -0800
Re: Effective uses of c `goto' statement Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-12-05 22:45 +0000
Re: Effective uses of c `goto' statement "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2020-12-11 19:33 -0800
Re: Effective uses of c `goto' statement Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-12-12 21:12 +0000
Re: Effective uses of c `goto' statement Bart <bc@freeuk.com> - 2020-12-05 12:49 +0000
Re: Effective uses of c `goto' statement Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-12-05 22:42 +0000
Re: Effective uses of c `goto' statement Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-12-06 05:46 -0800
Re: Effective uses of c `goto' statement Bart <bc@freeuk.com> - 2020-12-06 14:16 +0000
Re: Effective uses of c `goto' statement Öö Tiib <ootiib@hot.ee> - 2020-12-06 06:54 -0800
Re: Effective uses of c `goto' statement Bart <bc@freeuk.com> - 2020-12-06 16:19 +0000
Re: Effective uses of c `goto' statement Öö Tiib <ootiib@hot.ee> - 2020-12-06 15:34 -0800
Re: Effective uses of c `goto' statement Bart <bc@freeuk.com> - 2020-12-06 23:56 +0000
Re: Effective uses of c `goto' statement David Brown <david.brown@hesbynett.no> - 2020-12-07 11:11 +0100
Re: Effective uses of c `goto' statement Bart <bc@freeuk.com> - 2020-12-07 11:41 +0000
Re: Effective uses of c `goto' statement David Brown <david.brown@hesbynett.no> - 2020-12-07 15:35 +0100
Re: Effective uses of c `goto' statement Bart <bc@freeuk.com> - 2020-12-07 15:48 +0000
Re: Effective uses of c `goto' statement Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-12-07 11:46 -0800
Re: Effective uses of c `goto' statement Bart <bc@freeuk.com> - 2020-12-07 20:01 +0000
Re: Effective uses of c `goto' statement Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-12-07 13:03 -0800
Re: Effective uses of c `goto' statement David Brown <david.brown@hesbynett.no> - 2020-12-07 11:01 +0100
Re: Effective uses of c `goto' statement Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-12-07 03:35 -0800
Re: Effective uses of c `goto' statement Richard Damon <Richard@Damon-Family.org> - 2020-12-07 07:33 -0500
Re: Effective uses of c `goto' statement gazelle@shell.xmission.com (Kenny McCormack) - 2020-12-07 13:11 +0000
Re: Effective uses of c `goto' statement Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-12-07 05:24 -0800
Re: Effective uses of c `goto' statement Richard Damon <Richard@Damon-Family.org> - 2020-12-07 08:58 -0500
Re: Effective uses of c `goto' statement David Brown <david.brown@hesbynett.no> - 2020-12-07 15:48 +0100
Re: Effective uses of c `goto' statement David Brown <david.brown@hesbynett.no> - 2020-12-07 15:45 +0100
Re: Effective uses of c `goto' statement Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-12-07 07:29 -0800
Re: Effective uses of c `goto' statement Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-12-07 22:34 +0000
Re: Effective uses of c `goto' statement David Brown <david.brown@hesbynett.no> - 2020-12-07 15:38 +0100
Re: Effective uses of c `goto' statement kegs@provalid.com (Kent Dickey) - 2020-12-10 15:45 -0600
Re: Effective uses of c `goto' statement Vir Campestris <vir.campestris@invalid.invalid> - 2020-12-07 21:43 +0000
Re: Effective uses of c `goto' statement Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-12-07 23:02 +0000
Re: Effective uses of c `goto' statement Vir Campestris <vir.campestris@invalid.invalid> - 2020-12-10 21:15 +0000
Re: Effective uses of c `goto' statement Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-12-10 22:48 +0000
Re: Effective uses of c `goto' statement Vir Campestris <vir.campestris@invalid.invalid> - 2020-12-11 20:59 +0000
Re: Effective uses of c `goto' statement Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-12-11 14:07 -0800
Re: Effective uses of c `goto' statement Bonita Montero <Bonita.Montero@gmail.com> - 2020-12-05 08:55 +0100
Re: Effective uses of c `goto' statement Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-12-05 02:04 -0800
Re: Effective uses of c `goto' statement Vir Campestris <vir.campestris@invalid.invalid> - 2020-12-07 21:37 +0000
Re: Effective uses of c `goto' statement James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-12-07 17:03 -0500
Re: Effective uses of c `goto' statement David Brown <david.brown@hesbynett.no> - 2020-12-07 23:17 +0100
Re: Effective uses of c `goto' statement Kaz Kylheku <563-365-8930@kylheku.com> - 2020-12-07 22:19 +0000
Re: Effective uses of c `goto' statement Vir Campestris <vir.campestris@invalid.invalid> - 2020-12-10 21:13 +0000
Re: Effective uses of c `goto' statement kegs@provalid.com (Kent Dickey) - 2020-12-10 15:30 -0600
Re: Effective uses of c `goto' statement "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2020-12-05 13:01 -0500
Re: Effective uses of c `goto' statement luser droog <luser.droog@gmail.com> - 2020-12-11 19:27 -0800
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