while (1) vs. for ( ;; )

[pete]

Re: while (1) vs. for ( ;; )

Christian Bau wrote:[color=blue]
>
> In article <43127F62.1A60@ mindspring.com> ,
> pete <pfiland@mindsp ring.com> wrote:
>[color=green]
> > Michael B Allen wrote:[color=darkred]
> > >
> > > Should there be any preference
> > > between the following logically equivalent
> > > statements?
> > >
> > > while (1) {
> > >
> > > vs.
> > >
> > > for ( ;; ) {
> > >
> > > I suspect the answer is "no" but I'd
> > > like to know what the consensus is
> > > so that it doesn't blink through my mind anymore when I type it.[/color]
> >
> > while(1) gets a warning on my compiler.
> > for(;;) doesn't.[/color]
>
> Could you tell us which compiler? And could you check what it thinks
> about
>
> do {
> ...
> } while (0);
>[/color]

It doesn't like that one either.

--
pete

[Guillaume]

Re: while (1) vs. for ( ;; )

Randy Howard wrote:[color=blue]
> const hell_freezes_ov er = false;
>
> repeat
> something;
> until hell_freezes_ov er;
>
> Seems to convey the intent quite clearly. :-)[/color]

That is, if hell means anything to you. If it doesn't, then it does not
convey much. ;-)

[Richard Tobin]

Re: while (1) vs. for ( ;; )

In article <deu31g$dbn$1@e nyo.uwa.edu.au> ,
Chris McDonald <chris@csse.uwa .edu.au> wrote:
[color=blue]
>I'm sure that everyone reading this newsgroup understands the *role*
>of while(1) and for(;;) but, as suggested, consider how a beginner
>may read these the first few times.[/color]

If you're writing code for beginners to read you may well come to
different conclusions from those where you're writing a program to be
maintained by experienced programmers.

-- Richard

[Anton Petrusevich]

Re: while (1) vs. for ( ;; )

Chris McDonald wrote:
[color=blue]
> I would suggest that both while(1) and for(;;) are potentially unclear
> to a person (undergrad. student) seeing C for the first time
> (while assuming they haven't seen Java or C++, either).[/color]

What about following?
#defined loop_forever for(;;)
--
Anton Petrusevich

[Anton Petrusevich]

Re: while (1) vs. for ( ;; )

pete wrote:
[color=blue][color=green][color=darkred]
>> > while(1) gets a warning on my compiler.
>> > for(;;) doesn't.[/color]
>> Could you tell us which compiler? And could you check what it thinks
>> about
>> do {
>> ...
>> } while (0);
>>[/color]
> It doesn't like that one either.[/color]

What about following?
while(1 == 1) {
....
}
and
do {
....
} while(1 == 0);
--
Anton Petrusevich

[akarl]

Re: while (1) vs. for ( ;; )

Anton Petrusevich wrote:[color=blue]
> Chris McDonald wrote:
>
>[color=green]
>>I would suggest that both while(1) and for(;;) are potentially unclear
>>to a person (undergrad. student) seeing C for the first time
>>(while assuming they haven't seen Java or C++, either).[/color]
>
>
> What about following?
> #defined loop_forever for(;;)[/color]

Defining a new language with the macro preprocessor is seldom a good idea.

August

[Anton Petrusevich]

Re: while (1) vs. for ( ;; )

akarl wrote:
[color=blue][color=green][color=darkred]
>>> Chris McDonald wrote:[/color][/color][/color]
[color=blue][color=green][color=darkred]
>>> I would suggest that both while(1) and for(;;) are potentially unclear
>>> to a person (undergrad. student) seeing C for the first time
>>> (while assuming they haven't seen Java or C++, either).[/color][/color][/color]
[color=blue][color=green]
>> What about following?
>> #define loop_forever for(;;)[/color]
> Defining a new language with the macro preprocessor is seldom a good idea.[/color]

I agree with you, but I was asking Chris McDonald. :)
--
Anton Petrusevich

[Ben Pfaff]

Re: while (1) vs. for ( ;; )

Anton Petrusevich <casus@att-ltd.biz> writes:
[color=blue]
> What about following?
> #defined loop_forever for(;;)[/color]

As long as you want to be "cute":
#define ever ;;
for (ever) { ... }
(I would never use this.)
--
int main(void){char p[]="ABCDEFGHIJKLM NOPQRSTUVWXYZab cdefghijklmnopq rstuvwxyz.\
\n",*q="kl BIcNBFr.NKEzjwC IxNJC";int i=sizeof p/2;char *strchr();int putchar(\
);while(*q){i+= strchr(p,*q++)-p;if(i>=(int)si zeof p)i-=sizeof p-1;putchar(p[i]\
);}return 0;}

[Alan Balmer]

Re: while (1) vs. for ( ;; )

On Sun, 28 Aug 2005 21:36:51 -0400, Michael B Allen
<mba2000@ioplex .com> wrote:
[color=blue]
>Should there be any preference between the following logically equivalent
>statements?
>
> while (1) {
>
>vs.
>
> for ( ;; ) {
>
>I suspect the answer is "no" but I'd like to know what the consensus is
>so that it doesn't blink through my mind anymore when I type it.
>[/color]
They do exactly the same thing. I use the "for ever" form because some
of the compilers I use give a warning on while(1).
--
Al Balmer
Balmer Consulting
removebalmercon sultingthis@att .net

[Kenneth Brody]

Re: while (1) vs. for ( ;; )

Walter Roberson wrote:[color=blue]
>
> In article <pan.2005.08.29 .01.36.51.40360 4@ioplex.com>,
> Michael B Allen <mba2000@ioplex .com> wrote:[color=green]
> >Should there be any preference between the following logically equivalent
> >statements?[/color]
>[color=green]
> > while (1) {
> >vs.
> > for ( ;; ) {[/color][/color]

I typically read them as "while true" and "forever".
[color=blue][color=green]
> >I suspect the answer is "no" but I'd like to know what the consensus is
> >so that it doesn't blink through my mind anymore when I type it.[/color][/color]

They are functionally identical, and will possibly generate the same
machine code.
[color=blue]
> Just my opinion, but I would tend to use them in slightly different
> contexts.
>
> I would tend to use while(1) when I was looping for something that
> will occur at an indeterminate future time, such as EOF or an
> alarm signal.[/color]

I typically declare an "int done=0;" and then use "while (!done)" in
such cases. It just reads better to me and allows a "clean" exit from
the loop.
[color=blue]
> I would tend to use for(;;) when I was looping for something that
> will occur within a bounded time, but which is inconvenient to
> express through loop control variables, such as iterating through
> a set of data structures until a certain property is detected.
>
> To give it a different slant: for(;;) conveys "iteration" , whereas
> while(1) conveys "repetition " that is not necessarily iterative.
>
> But as the two work out the same in the end, the choice amounts
> to no more than a hint to a human reader.[/color]

True.

--
+-------------------------+--------------------+-----------------------------+
| Kenneth J. Brody | www.hvcomputer.com | |
| kenbrody/at\spamcop.net | www.fptech.com | #include <std_disclaimer .h> |
+-------------------------+--------------------+-----------------------------+
Don't e-mail me at: <mailto:ThisIsA SpamTrap@gmail. com>

[Alan Balmer]

Re: while (1) vs. for ( ;; )

On Mon, 29 Aug 2005 08:42:47 +0000 (UTC), Richard Heathfield
<invalid@invali d.invalid> wrote:
[color=blue]
>Michael B Allen said:
>[color=green]
>> Should there be any preference between the following logically equivalent
>> statements?
>>
>> while (1) {
>>
>> vs.
>>
>> for ( ;; ) {
>>
>> I suspect the answer is "no" but I'd like to know what the consensus is
>> so that it doesn't blink through my mind anymore when I type it.[/color]
>
>while(1) will be flagged by many compilers as "conditiona l expression is
>constant" or some such wording, whereas for(;;) will not be. Consequently,
>for(;;) is preferable out of these two choices.
>
>Personally, I prefer neither choice! I would rather have the loop control
>statement explicitly document the exit condition (unless there genuinely
>isn't one, such as might be the case in an electronic appliance like a
>microwave oven, where "forever" can roughly be translated as "whilst power
>is being supplied to the appliance").[/color]

It often happens that there are multiple exit conditions. Is it your
preference to set a "get out" flag for these situations? That's my
preference, though I don't feel strongly about it (and I'm likely to
use multiple function returns, too, when a single return is too
contrived.)
--
Al Balmer
Balmer Consulting
removebalmercon sultingthis@att .net

[Randy Howard]

Re: while (1) vs. for ( ;; )

Guillaume wrote
(in article <43130cab$0$212 96$7a628cd7@new s.club-internet.fr>):
[color=blue]
> Randy Howard wrote:[color=green]
>> const hell_freezes_ov er = false;
>>
>> repeat
>> something;
>> until hell_freezes_ov er;
>>
>> Seems to convey the intent quite clearly. :-)[/color]
>
> That is, if hell means anything to you. If it doesn't, then it does not
> convey much. ;-)[/color]

It seems that the expression "when hell freezes over" is not as
widespread as I thought. :-)



--
Randy Howard (2reply remove FOOBAR)

[Richard Heathfield]

Re: while (1) vs. for ( ;; )

Alan Balmer said:
[color=blue]
> On Mon, 29 Aug 2005 08:42:47 +0000 (UTC), Richard Heathfield
> <invalid@invali d.invalid> wrote:
>[color=green]
>>Personally, I prefer neither choice! I would rather have the loop control
>>statement explicitly document the exit condition (unless there genuinely
>>isn't one, such as might be the case in an electronic appliance like a
>>microwave oven, where "forever" can roughly be translated as "whilst power
>>is being supplied to the appliance").[/color]
>
> It often happens that there are multiple exit conditions. Is it your
> preference to set a "get out" flag for these situations?[/color]

Yes: done = 1;
[color=blue]
> That's my
> preference, though I don't feel strongly about it (and I'm likely to
> use multiple function returns, too, when a single return is too
> contrived.)[/color]

I'm quite unlikely to use multiple returns, although I seem to recall that I
have done so on occasion, when in a tearing hurry.

--
Richard Heathfield
"Usenet is a strange place" - dmr 29 July 1999

http://www.cpax.org.uk

Email rjh at the above domain

[Guillaume]

Re: while (1) vs. for ( ;; )

Randy Howard wrote:[color=blue]
> It seems that the expression "when hell freezes over" is not as
> widespread as I thought. :-)[/color]

Lol, I was just being difficult. ;-)

[pete]

Re: while (1) vs. for ( ;; )

Anton Petrusevich wrote:[color=blue]
>
> pete wrote:
>[color=green][color=darkred]
> >> > while(1) gets a warning on my compiler.
> >> > for(;;) doesn't.
> >> Could you tell us which compiler? And could you check what it thinks
> >> about
> >> do {
> >> ...
> >> } while (0);
> >>[/color]
> > It doesn't like that one either.[/color]
>
> What about following?
> while(1 == 1) {
> ...
> }
> and
> do {
> ...
> } while(1 == 0);[/color]

My compiler warns about a constant expression being
he condition in a loop.
(1 == 1) and (1 == 0) are both such constant expressions.

--
pete