code question

[Ian Collins]

Re: code question

Bill Cunningham wrote:

"Barry Schwarz" <schwarzb@dqel. comwrote in message
news:7fe8d4def7 j0qh98uumds7bt8 ae0635kvc@4ax.c om...

>On Fri, 19 Sep 2008 16:52:17 -0400, "Bill Cunningham"
><nospam@nspam. invalidwrote:

>

>> if ((fp = fopen(argv[4], "a")) == NULL) {

>At the same time, it should be a file name.
>>
>That doesn't strike you as slightly odd?
>>

A filename input is an argument. I thought you treated it as such. There are
many things that kandr2 doesn't teach you.

Like common sense?

--
Ian Collins.

[Richard]

Re: code question

Ben Bacarisse <ben.usenet@bsb .me.ukwrites:

Richard<rgrdev@ gmail.comwrites :
>

>"Bill Cunningham" <nospam@nspam.i nvalidwrites:
>>

>>"Ian Collins" <ian-news@hotmail.co mwrote in message
>>news:6jimldF3 8973U6@mid.indi vidual.net...

<snip>

>>> unsigned n = 1;
>>> while ( n < argc ) {
>>> data[n-1] = strtod(argv[n], NULL);
>>> ++n;
>>>
>>[snip]
>>>
>>What's above is a bit of a different method than I would think of. Is that n
>>minus 1 in the brackets?
>>Why set n to 1?

<snip>

>To confuse you I assume. Its not a very C way of doing it IMO. Not
>tested for ISO C correctness or whether it even works but this is much
>clearer if you (and you must as a c programmer) understand for
>loops. You should get the idea.
>>
> for(int n=0;n<argc;n++)
> data[n] = strtod(argv[n+1], NULL);

>
Great disclaimer! "This is better (but it may be wrong)". Yes it is
(wrong). Here is the flaw with using a debugger. It is easier to
think about this code than to paste this into a main function and
debug it.

I noticed it when hitting return as the thread will show you. Whoops
indeed. And I never used a debugger so where that came from I'm not
sure. My reference to a debugger before was for Bill to see where he seg
faulted with zero arguments.

[Richard]

Re: code question

Bill Cunningham <nospam@nspam.i nvalidwrites:

Richard wrote:
>

>And while I am at it, please stop spamming the application development
>groups telling them you are trying to write a printer driver when you
>could not even tell them the type of printer you are using.

>
[Testing out THunderbird]
>
Go back a read the thread for what it says. We were conversing about
my printer make and model. I don't need to defend what's posted.

I know what was said in the thread. You told the guys you wanted to
write a printer driver for it.

[Richard]

Re: code question

Ian Collins <ian-news@hotmail.co mwrites:

Bill Cunningham wrote:

>"Barry Schwarz" <schwarzb@dqel. comwrote in message
>news:7fe8d4def 7j0qh98uumds7bt 8ae0635kvc@4ax. com...

>>On Fri, 19 Sep 2008 16:52:17 -0400, "Bill Cunningham"
>><nospam@nspam .invalidwrote:

>>

>>> if ((fp = fopen(argv[4], "a")) == NULL) {
>>At the same time, it should be a file name.
>>>
>>That doesn't strike you as slightly odd?
>>>

>A filename input is an argument. I thought you treated it as such. There are
>many things that kandr2 doesn't teach you.

>
Like common sense?

Amazing stuff. Really. If he's a troll (and I really think he is) then
he's damn good.

[Ian Collins]

Re: code question

Richard wrote:

Ian Collins <ian-news@hotmail.co mwrites:
>

>Bill Cunningham wrote:

>>"Barry Schwarz" <schwarzb@dqel. comwrote in message
>>news:7fe8d4de f7j0qh98uumds7b t8ae0635kvc@4ax .com...
>>>On Fri, 19 Sep 2008 16:52:17 -0400, "Bill Cunningham"
>>><nospam@nspa m.invalidwrote:
>>>> if ((fp = fopen(argv[4], "a")) == NULL) {
>>>At the same time, it should be a file name.
>>>>
>>>That doesn't strike you as slightly odd?
>>>>
>>A filename input is an argument. I thought you treated it as such. There are
>>many things that kandr2 doesn't teach you.

>Like common sense?

>
Amazing stuff. Really. If he's a troll (and I really think he is) then
he's damn good.

Hell, I'm working on a sunny Saturday afternoon so a bit of light
entertainment is called for!

--
Ian Collins.

[blargg]

Re: code question

In article <gb1lqt$m5j$3@r egistered.motza rella.org>,
Richard<rgrdev@ gmail.comwrote:

Ian Collins <ian-news@hotmail.co mwrites:
>

Bill Cunningham wrote:

"Barry Schwarz" <schwarzb@dqel. comwrote in message
news:7fe8d4def7 j0qh98uumds7bt8 ae0635kvc@4ax.c om...
>On Fri, 19 Sep 2008 16:52:17 -0400, "Bill Cunningham"
><nospam@nspam. invalidwrote:
>
>> if ((fp = fopen(argv[4], "a")) == NULL) {
>At the same time, it should be a file name.
>>
>That doesn't strike you as slightly odd?
>>
A filename input is an argument. I thought you treated it as such.

There are

many things that kandr2 doesn't teach you.

Like common sense?

>
Amazing stuff. Really. If he's a troll (and I really think he is) then
he's damn good.

And in a way, that makes him an excellent programmer of the wetware of the
people who just can't help not responding to him, time after time after
time.

[CBFalconer]

Re: code question

Andrew Poelstra wrote:

Bill Cunningham <nospam@nspam.i nvalidwrote:
>

>Thanks Richard I know I can always count on you. I wondered about
>argc and its uses.

>
In addition to argc, argv is also NULL terminated (IIRC!), so
you can loop through it without needed argc to find out when
to stop.
>
while(*argv)
{
process(*argv);
++argv;
}

I'm not sure that is safe. Check whether argv[0] can be a NULL.

--
[mail]: Chuck F (cbfalconer at maineline dot net)
[page]: <http://cbfalconer.home .att.net>
Try the download section.

[CBFalconer]

Re: code question

Bill Cunningham wrote:

>
Someone pointed out to me Richard that an answer to a question I
raised about bitwise operators was on page 49 or kandr2. I read,
and re-read, and re-read page 49 about 3 times and strained to
keep my focus on reading and the text. The question was why is
the unary operator ~ shown like this:
>
x~34;
and not x=x~34;
>
Is the question indeed answered on that page?

Are you sure it is not "x ~= 34;"? Have you checked the published
errata sheet? I greatly doubt that K&R have suppressed the blanks
as you have.

--
[mail]: Chuck F (cbfalconer at maineline dot net)
[page]: <http://cbfalconer.home .att.net>
Try the download section.

[Ian Collins]

Re: code question

CBFalconer wrote:

Andrew Poelstra wrote:

>Bill Cunningham <nospam@nspam.i nvalidwrote:
>>

>>Thanks Richard I know I can always count on you. I wondered about
>>argc and its uses.

>In addition to argc, argv is also NULL terminated (IIRC!), so
>you can loop through it without needed argc to find out when
>to stop.
>>
>while(*argv)
>{
> process(*argv);
> ++argv;
>}

>
I'm not sure that is safe. Check whether argv[0] can be a NULL.
>

Did you bother to read Richard's reply?

--
Ian Collins.

[Andrew Poelstra]

Re: code question

On 2008-09-20, CBFalconer <cbfalconer@yah oo.comwrote:

Andrew Poelstra wrote:

>Bill Cunningham <nospam@nspam.i nvalidwrote:
>>

>>Thanks Richard I know I can always count on you. I wondered about
>>argc and its uses.

>>
>In addition to argc, argv is also NULL terminated (IIRC!), so
>you can loop through it without needed argc to find out when
>to stop.
>>
>while(*argv)
>{
> process(*argv);
> ++argv;
>}

>
I'm not sure that is safe. Check whether argv[0] can be a NULL.
>

Oops! The first line should be
while(argv)
or
while(argv != NULL)

...without the dereference.

--
Andrew Poelstra apoelstra@wpsof tware.net
That was a joke. Jokes in mathematics, are sometimes not funny.
-Veselin Jungic

[Richard Heathfield]

Re: code question

Bill Cunningham said:

Someone pointed out to me Richard that an answer to a question I
raised
about bitwise operators was on page 49 or kandr2. I read, and re-read,
and re-read page 49 about 3 times and strained to keep my focus on
reading and the text. The question was why is the unary operator ~ shown
like this:
>
x~34;
and not x=x~34;

I have read page 49 from top to bottom and back again, and can't even find
34 on that page, let alone x~34. Perhaps you could tell me on which line
the ~ operator is shown as x~34?

--
Richard Heathfield <http://www.cpax.org.uk >
Email: -http://www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999

[Richard Heathfield]

Re: code question

Andrew Poelstra said:

On 2008-09-20, CBFalconer <cbfalconer@yah oo.comwrote:

>Andrew Poelstra wrote:

>>Bill Cunningham <nospam@nspam.i nvalidwrote:
>>>
>>>Thanks Richard I know I can always count on you. I wondered about
>>>argc and its uses.
>>>
>>In addition to argc, argv is also NULL terminated (IIRC!), so
>>you can loop through it without needed argc to find out when
>>to stop.
>>>
>>while(*argv )
>>{
>> process(*argv);
>> ++argv;
>>}

>>
>I'm not sure that is safe. Check whether argv[0] can be a NULL.
>>

>
Oops! The first line should be
while(argv)
or
while(argv != NULL)
>
..without the dereference.

No, you were right the first time.

--
Richard Heathfield <http://www.cpax.org.uk >
Email: -http://www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999

[Andrew Poelstra]

Re: code question

On 2008-09-20, Richard Heathfield <rjh@see.sig.in validwrote:

Andrew Poelstra said:
>

>On 2008-09-20, CBFalconer <cbfalconer@yah oo.comwrote:

>>Andrew Poelstra wrote:
>>>Bill Cunningham <nospam@nspam.i nvalidwrote:
>>>>
>>>>Thanks Richard I know I can always count on you. I wondered about
>>>>argc and its uses.
>>>>
>>>In addition to argc, argv is also NULL terminated (IIRC!), so
>>>you can loop through it without needed argc to find out when
>>>to stop.
>>>>
>>>while(*arg v)
>>>{
>>> process(*argv);
>>> ++argv;
>>>}
>>>
>>I'm not sure that is safe. Check whether argv[0] can be a NULL.
>>>

>>
>Oops! The first line should be
> while(argv)
>or
> while(argv != NULL)
>>
>..without the dereference.

>
No, you were right the first time.
>

Oh, I see. I guess I need more sleep before working with
pointers to pointers any more. =P

--
Andrew Poelstra apoelstra@wpsof tware.net
That was a joke. Jokes in mathematics, are sometimes not funny.
-Veselin Jungic

[Richard]

Re: code question

Andrew Poelstra <apoelstra@supe rnova.homewrite s:

On 2008-09-20, CBFalconer <cbfalconer@yah oo.comwrote:

>Andrew Poelstra wrote:

>>Bill Cunningham <nospam@nspam.i nvalidwrote:
>>>
>>>Thanks Richard I know I can always count on you. I wondered about
>>>argc and its uses.
>>>
>>In addition to argc, argv is also NULL terminated (IIRC!), so
>>you can loop through it without needed argc to find out when
>>to stop.
>>>
>>while(*argv )
>>{
>> process(*argv);
>> ++argv;
>>}

>>
>I'm not sure that is safe. Check whether argv[0] can be a NULL.
>>

>
Oops! The first line should be
while(argv)
or
while(argv != NULL)
>
..without the dereference.

No. With the dereference. Not a typo so a fundamental misunderstandin g
of the basic use of pointers there. I can only assume beer has been
consumed :-;

[Richard]

Re: code question

Ian Collins <ian-news@hotmail.co mwrites:

CBFalconer wrote:

>Andrew Poelstra wrote:

>>Bill Cunningham <nospam@nspam.i nvalidwrote:
>>>
>>>Thanks Richard I know I can always count on you. I wondered about
>>>argc and its uses.
>>In addition to argc, argv is also NULL terminated (IIRC!), so
>>you can loop through it without needed argc to find out when
>>to stop.
>>>
>>while(*argv )
>>{
>> process(*argv);
>> ++argv;
>>}

>>
>I'm not sure that is safe. Check whether argv[0] can be a NULL.
>>

Did you bother to read Richard's reply?

Interestingly enough I must admit to never having seen or heard of that
before.

And I guess the resulting C code would be something like:

for(;*argv;proc ess(*argv++));

or

for(char *p=*argv++; p; process(p));

Since you have to read the contents of the address pointed to by argv
anyway the compiler is clever enough in most cases to mean that using a
decrement and branch like argc-- is not any faster except for the last
null case.