[9fans] A Plan 9 C request....

[9fans] A Plan 9 C request....

[Dan Cross]

Here's a request for my favorite C feature from C99, which isn't yet in
Plan 9 C.  I'd really like it if one could write statements of the form,

	for (int i = 0; i < 10; i++);

or

	for (char *p = s; *p != '\0'; p++);

That is, declare variables in the first part of a for loop.  That would
be nice.  Anyone care to add it to the compiler?  I'd try it myself, but
I'm just too busy right now....

	- Dan C.

Re: [9fans] A Plan 9 C request....

[Skip Tavakkolian]

when it was added to C++, i "felt" that the scope
of 'i' wasn't natural; it goes beyond 'for's closure.
i like a behavior like this:

	{ int i; for (i = 0, ...) ...; }

> Here's a request for my favorite C feature from C99, which isn't yet in
> Plan 9 C.  I'd really like it if one could write statements of the form,
>
> 	for (int i = 0; i < 10; i++);
>
> or
>
> 	for (char *p = s; *p != '\0'; p++);
>
> That is, declare variables in the first part of a for loop.  That would
> be nice.  Anyone care to add it to the compiler?  I'd try it myself, but
> I'm just too busy right now....

Re: [9fans] A Plan 9 C request....

[Brantley Coile]

> when it was added to C++, i "felt" that the scope
> of 'i' wasn't natural; it goes beyond 'for's closure.
> i like a behavior like this:

I think the scope shouldn't extend past the first semicolon. :)

/* Boyd Roberts Memorial Obnoxious Comment Society member */

Re: [9fans] A Plan 9 C request....

[rog]

> when it was added to C++, i "felt" that the scope
> of 'i' wasn't natural; it goes beyond 'for's closure.
> i like a behavior like this:
>
> 	{ int i; for (i = 0, ...) ...; }

when i first started to use Limbo, which has a similar looking
idiom, i thought the same.

	for(i := 0; i < 10; i++) {
	}

but actually, having the variable
available outside the scope is so often useful,
e.g.
	for(i := 0; i < end; i++)
		if(sometest())
			break;
	if(i == end)
		fall_through_condition();

that i now think the non-scoping behaviour is the right thing.

i'm not sure that it's worth adding to plan 9 C though.

Re: [9fans] A Plan 9 C request....

[Russ Cox]

> when it was added to C++, i "felt" that the scope
> of 'i' wasn't natural; it goes beyond 'for's closure.
> i like a behavior like this:
>
> 	{ int i; for (i = 0, ...) ...; }

so did the c++ standards committee and the c99 committee.
both have declared that

	for (int i = 0; i < 10; i++);

now means

	{ int i; for(i=0; i<10; i++); }

russ

Re: [9fans] A Plan 9 C request....

[Richard Bilson]

On 3/1/06, Skip Tavakkolian <9nut@9netics.com> wrote:
> when it was added to C++, i "felt" that the scope
> of 'i' wasn't natural; it goes beyond 'for's closure.
> i like a behavior like this:
>
>         { int i; for (i = 0, ...) ...; }

This (the way you like it) is the way it was eventually standardized
in C++. Any modern compiler that I have used does it this way.

Re: [9fans] A Plan 9 C request....

[Brantley Coile]

> now means
>
> 	{ int i; for(i=0; i<10; i++); }

Does that mean the following will compile?

void
f(void)
{
	i = 3;
	put(i);
	for (int i = 0; i < 3; i++)
		put(i);
	if (i == 4) put(4);
}

Re: [9fans] A Plan 9 C request....

[Skip Tavakkolian]

>> when it was added to C++, i "felt" that the scope
>> of 'i' wasn't natural; it goes beyond 'for's closure.
>> i like a behavior like this:
>>
>> 	{ int i; for (i = 0, ...) ...; }
>
> so did the c++ standards committee and the c99 committee.
> both have declared that
>
> 	for (int i = 0; i < 10; i++);
>
> now means
>
> 	{ int i; for(i=0; i<10; i++); }

i didn't know. wow?!
my vc6 is officially an antique.

Re: [9fans] A Plan 9 C request....

[Russ Cox]

> Does that mean the following will compile?
>
>     1	void
>     2	f(void)
>     3	{
>     4		i = 3;
>     5		put(i);
>     6		for (int i = 0; i < 3; i++)
>     7			put(i);
>     8		if (i == 4) put(4);
>     9	}

No, because i is undeclared at line 4.
It's still not a good example.  Here's a better one:

void
main(void)
{
	int i = 100;
	for (int i = 0; i < 3; i++)
		printf("%d\n", i);
	printf("%d\n", i);
}

It prints 0 1 2 100.

Russ

Re: [9fans] A Plan 9 C request....

[jmk]

The C Rationale (6.8.5.3) says:

	int i = 42;
	for (int i = 5, j = 15; i < 10; i++, j--)
		printf("Loop %d %d\n",, i, j);
	printf("I = %d\n", i);	// there is no j in scope

will output

	Loop 5 15
	Loop 6 14
	Loop 7 13
	Loop 8 12
	Loop 9 11
	I = 42

On Wed Mar  1 13:26:33 EST 2006, brantley@coraid.com wrote:
> > now means
> >
> > 	{ int i; for(i=0; i<10; i++); }
>
> Does that mean the following will compile?
>
> void
> f(void)
> {
> 	i = 3;
> 	put(i);
> 	for (int i = 0; i < 3; i++)
> 		put(i);
> 	if (i == 4) put(4);
> }

Re: [9fans] A Plan 9 C request....

[Ronald G Minnich]

Brantley Coile wrote:
>>now means
>>
>>	{ int i; for(i=0; i<10; i++); }
> 
> 
> Does that mean the following will compile?
> 
> void
> f(void)
> {
> 	i = 3;
> 	put(i);
> 	for (int i = 0; i < 3; i++)
> 		put(i);
> 	if (i == 4) put(4);
> }
> 

  cat > t.c
void
f(void)
{
         i = 3;
         put(i);
         for (int i = 0; i < 3; i++)
                 put(i);
         if (i == 4) put(4);
}
[rminnich@q tmp]$ cc t.c
t.c: In function ‘f’:
t.c:4: error: ‘i’ undeclared (first use in this function)
t.c:4: error: (Each undeclared identifier is reported only once
t.c:4: error: for each function it appears in.)
t.c:6: error: ‘for’ loop initial declaration used outside C99 mode
[rminnich@q tmp]$


ron

Re: [9fans] A Plan 9 C request....

[David Leimbach]

On 3/1/06, Skip Tavakkolian <9nut@9netics.com> wrote:
> >> when it was added to C++, i "felt" that the scope
> >> of 'i' wasn't natural; it goes beyond 'for's closure.
> >> i like a behavior like this:
> >>
> >>      { int i; for (i = 0, ...) ...; }
> >
> > so did the c++ standards committee and the c99 committee.
> > both have declared that
> >
> >       for (int i = 0; i < 10; i++);
> >
> > now means
> >
> >       { int i; for(i=0; i<10; i++); }
>
> i didn't know. wow?!
> my vc6 is officially an antique.
>
>


VC *anything* should not be seen as an implementation of any standards :).

I've heard the .NET stuff is better but they've added a ton of
extensions to "managed C++" that really isn't C++ anymore.

In fact I was told they were lobbying to get that stuff into the
standard but Bjarne isn't favorable to language changes that he thinks
could be solved in libraries.

Dave

Re: [9fans] A Plan 9 C request....

[Andrew R. Reiter]

On Wed, 1 Mar 2006, David Leimbach wrote:

:On 3/1/06, Skip Tavakkolian <9nut@9netics.com> wrote:
:> >> when it was added to C++, i "felt" that the scope
:> >> of 'i' wasn't natural; it goes beyond 'for's closure.
:> >> i like a behavior like this:
:> >>
:> >>      { int i; for (i = 0, ...) ...; }
:> >
:> > so did the c++ standards committee and the c99 committee.
:> > both have declared that
:> >
:> >       for (int i = 0; i < 10; i++);
:> >
:> > now means
:> >
:> >       { int i; for(i=0; i<10; i++); }
:>
:> i didn't know. wow?!
:> my vc6 is officially an antique.
:>
:>
:
:
:VC *anything* should not be seen as an implementation of any standards :).
:

As a person who's done porting of embedded systems between compilers and
just working with VC, gcc, icc, et al, in general, I couldn't agree more!

$0.02
Andrew

--
arr@watson.org

Re: [9fans] A Plan 9 C request....

[Devon H. O'Dell]

2006/3/1, Ronald G Minnich <rminnich@lanl.gov>:
> Brantley Coile wrote:
> >>now means
> >>
> >>      { int i; for(i=0; i<10; i++); }
> >
> >
> > Does that mean the following will compile?
> >
> > void
> > f(void)
> > {
> >       i = 3;
> >       put(i);
> >       for (int i = 0; i < 3; i++)
> >               put(i);
> >       if (i == 4) put(4);
> > }
> >
>
>   cat > t.c
> void
> f(void)
> {
>          i = 3;
>          put(i);
>          for (int i = 0; i < 3; i++)
>                  put(i);
>          if (i == 4) put(4);
> }
> [rminnich@q tmp]$ cc t.c
> t.c: In function 'f':
> t.c:4: error: 'i' undeclared (first use in this function)
> t.c:4: error: (Each undeclared identifier is reported only once
> t.c:4: error: for each function it appears in.)
> t.c:6: error: 'for' loop initial declaration used outside C99 mode
> [rminnich@q tmp]$
>
>
> ron

And the reason it doesn't is because in this code snippet, the
variable i is undeclared. I assume since the i is not declared, the
compiler steps out of C99 mode and refuses to allow the C99 construct
of for (int i...)

--Devon

Re: [9fans] A Plan 9 C request....

[Brantley Coile]

> As a person who's done porting of embedded systems between compilers and
> just working with VC, gcc, icc, et al, in general, I couldn't agree more!
>
> $0.02
> Andrew

After Ken's compiler, lcc is my favorite C compiler.  Ah, for the days
when C and I were young, and all the compilers were Steve' pcc.  I
never got a chance to use Dennis' compiler in the heat of battle, but
it's code is a wonder to behold.  It's evolution from NB to C is the
best example I've seen of entropy in reverse.

 Brantley

Re: [9fans] A Plan 9 C request....

[Richard Miller]

> in the section after the /* storage */ comment in c00.c
>
> 	regtab 0;
> 	efftab 1;
> [etc.]
>
> should this be read as
>
> 	int regtab = 0;
> 	int efftab = 1;

Yes.

Re: [9fans] A Plan 9 C request....

[erik quanstrom]

in the section after the /* storage */ comment in c00.c

	regtab 0;
	efftab 1;
[etc.]

should this be read as

	int regtab = 0;
	int efftab = 1;

?

- erik

Brantley Coile <brantley@coraid.com> writes

|
| --upas-sxzcqiogirovolmsuexgarfigy
|
| http://plan9.bell-labs.com/cm/cs/who/dmr/primevalC.html
|
| See the above for the evolution of the code.
|
| --upas-sxzcqiogirovolmsuexgarfigy
| To: Fans of the OS Plan 9 from Bell Labs <9fans@cse.psu.edu>,
| 	9fans@cse.psu.edu,
| 	Richard Miller <9fans@hamnavoe.com>
| References: <aa5409a26b13f8535c296cfdb9dedc2f@hamnavoe.com>
| In-Reply-To: <aa5409a26b13f8535c296cfdb9dedc2f@hamnavoe.com>
| Subject: Re: [9fans] A Plan 9 C request....
|
| > :  never got a chance to use Dennis' compiler in the heat of battle, but
| > :  it's code is a wonder to behold.  It's evolution from NB to C is the
| > :  best example I've seen of entropy in reverse.
| >
| > Could we see the code?
|
| http://www.tuhs.org/Archive/PDP-11/Distributions/research/Dennis_v6/v6src.tar.gz
|
| Look in directory 'c'.

Re: [9fans] A Plan 9 C request....

[Brantley Coile]

[-- Attachment #1: Type: text/plain, Size: 105 bytes --]

http://plan9.bell-labs.com/cm/cs/who/dmr/primevalC.html

See the above for the evolution of the code.

[-- Attachment #2: Type: message/rfc822, Size: 2440 bytes --]

From: Richard Miller <9fans@hamnavoe.com>
To: 9fans@cse.psu.edu
Subject: Re: [9fans] A Plan 9 C request....
Date: Thu, 2 Mar 2006 12:14:31 +0000
Message-ID: <aa5409a26b13f8535c296cfdb9dedc2f@hamnavoe.com>

> :  never got a chance to use Dennis' compiler in the heat of battle, but
> :  it's code is a wonder to behold.  It's evolution from NB to C is the
> :  best example I've seen of entropy in reverse.
>
> Could we see the code?

http://www.tuhs.org/Archive/PDP-11/Distributions/research/Dennis_v6/v6src.tar.gz

Look in directory 'c'.

Re: [9fans] A Plan 9 C request....

[Anthony Sorace]

also interesting, in terms of evolution:

http://www.cs.bell-labs.com/who/dmr/primevalC.html

Re: [9fans] A Plan 9 C request....

[Richard Miller]

> :  never got a chance to use Dennis' compiler in the heat of battle, but
> :  it's code is a wonder to behold.  It's evolution from NB to C is the
> :  best example I've seen of entropy in reverse.
>
> Could we see the code?

http://www.tuhs.org/Archive/PDP-11/Distributions/research/Dennis_v6/v6src.tar.gz

Look in directory 'c'.

Re: [9fans] A Plan 9 C request....

[Fco. J. Ballesteros]

:  After Ken's compiler, lcc is my favorite C compiler.  Ah, for the days
:  when C and I were young, and all the compilers were Steve' pcc.  I
:  never got a chance to use Dennis' compiler in the heat of battle, but
:  it's code is a wonder to behold.  It's evolution from NB to C is the
:  best example I've seen of entropy in reverse.

Could we see the code?