while (1) vs. for ( ;; )

[Michael B Allen]

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.

Mike

[caduardo21@yahoo.com.br]

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

You're right. The answer is no. They'll both do the exact same thing.

[Walter Roberson]

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

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

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.

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.
--
Daylight is a trademark of OSRAM SYLVANIA INC.

[Guillaume]

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

Question of style, nothing else.
Personally, I tend to prefer 'for (;;)', but that's just my style.

It's like asking which is better:

if () {
}

or:

if ()
{
}

I use the second form exclusively for various reasons, but it's a matter
of style. Doesn't change the code one bit.

[Robert Gamble]

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

Michael B Allen 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]

Many consider the latter preferable, it can be read as "for-ever" and
makes the intention of the programmer clearer. "while" implies a
predicate which may not always be true whereas "for" does not.

Robert Gamble

[Chris McDonald]

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

Michael B Allen <mba2000@ioplex .com> writes:
[color=blue]
>Should there be any preference between the following logically equivalent
>statements?[/color]
[color=blue]
> while (1) {
>vs.
> for ( ;; ) {[/color]
[color=blue]
>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]


Preference? Why not move on to something whose intention is clear:

while(true) {

--
Chris.

[Ben Pfaff]

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

Chris McDonald <chris@csse.uwa .edu.au> writes:
[color=blue]
> Michael B Allen <mba2000@ioplex .com> writes:
>[color=green]
>>Should there be any preference between the following logically equivalent
>>statements?[/color]
>[color=green]
>> while (1) {
>>vs.
>> for ( ;; ) {[/color]
>[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]
>
> Preference? Why not move on to something whose intention is clear:
>
> while(true) {[/color]

In what way are the former two statements' intentions not clear?
Both of them obviously loop "forever".
--
A competent C programmer knows how to write C programs correctly,
a C expert knows enough to argue with Dan Pop, and a C expert
expert knows not to bother.

[pete]

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

Michael B Allen 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]

while(1) gets a warning on my compiler.
for(;;) doesn't.

--
pete

[Chris McDonald]

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

Ben Pfaff <blp@cs.stanfor d.edu> writes:
[color=blue]
>Chris McDonald <chris@csse.uwa .edu.au> writes:[/color]
[color=blue][color=green]
>> Michael B Allen <mba2000@ioplex .com> writes:
>>[color=darkred]
>>>Should there be any preference between the following logically equivalent
>>>statements ?[/color]
>>[color=darkred]
>>> while (1) {
>>>vs.
>>> for ( ;; ) {[/color]
>>[color=darkred]
>>>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]
>>
>> Preference? Why not move on to something whose intention is clear:
>>
>> while(true) {[/color][/color]
[color=blue]
>In what way are the former two statements' intentions not clear?
>Both of them obviously loop "forever".[/color]


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).

OK, I suggest that while(true) is *clearer*.

--
Chris.

[Keith Thompson]

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

Chris McDonald <chris@csse.uwa .edu.au> writes:
[...][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]

I would suggest that anyone who doesn't understand while(1) or for(;;)
isn't going to have much chance of understanding what follows it.

--
Keith Thompson (The_Other_Keit h) kst-u@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.

[Chris McDonald]

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

Keith Thompson <kst-u@mib.org> writes:
[color=blue]
>Chris McDonald <chris@csse.uwa .edu.au> writes:
>[...][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][/color]
[color=blue]
>I would suggest that anyone who doesn't understand while(1) or for(;;)
>isn't going to have much chance of understanding what follows it.[/color]


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.

I believe that it's these little points that can make one textbook a
better introduction than another. It's difficult to argue for the
continued writing of new code that could be written in a clearer fashion.

--
Chris.

[Randy Howard]

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

Robert Gamble wrote
(in article
<1125282206.880 912.35420@f14g2 000cwb.googlegr oups.com>):
[color=blue]
> Michael B Allen wrote:[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]
>
> Many consider the latter preferable, it can be read as "for-ever" and
> makes the intention of the programmer clearer. "while" implies a
> predicate which may not always be true whereas "for" does not.[/color]

This is where Pascal has an advantage. (I probably have some of
the syntax wrong, I haven't written any Pascal since the late
80s)

const hell_freezes_ov er = false;

repeat
something;
until hell_freezes_ov er;

Seems to convey the intent quite clearly. :-)

--
Randy Howard (2reply remove FOOBAR)

[Richard Heathfield]

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

Michael B Allen said:
[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]

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").


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

http://www.cpax.org.uk

Email rjh at the above domain

[Christian Bau]

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

In article <43127F62.1A60@ mindspring.com> ,
pete <pfiland@mindsp ring.com> wrote:
[color=blue]
> Michael B Allen wrote:[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) 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);

?

[akarl]

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

Randy Howard wrote:[color=blue]
> Robert Gamble wrote
> (in article
> <1125282206.880 912.35420@f14g2 000cwb.googlegr oups.com>):
>
>[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]
>>
>>Many consider the latter preferable, it can be read as "for-ever" and
>>makes the intention of the programmer clearer. "while" implies a
>>predicate which may not always be true whereas "for" does not.[/color]
>
>
> This is where Pascal has an advantage. (I probably have some of
> the syntax wrong, I haven't written any Pascal since the late
> 80s)
>
> const hell_freezes_ov er = false;
>
> repeat
> something;
> until hell_freezes_ov er;
>
> Seems to convey the intent quite clearly. :-)[/color]

Well, in C we have the similar do-while statement. In Modula on the
other hand there is a real exit-in-the-middle loop construct:

LOOP
...
IF someCondition THEN EXIT END;
...
END


August