Fergus Henderson <fjh@mundook.cs.mu.OZ.AU> wrote:
>>If the compilers are right and I am wrong, how do I initialize my "char *
>>s" in the first part of the "for" loop ?
>
>One way is to move the declaration of `i' to before the for loop:
>
>   char * st = "Test";
>   char * s;
>   int i;
>   for (i = 0, s = st; i < 2; ++i)

It's probably better to move the "s = st" out of the loop:

 char * st = "Test";
 char * s = st;
 for (int i = 0; i < 2; ++i )

The advantages are:

(1) Everything is intialized right away (good style, I'm told),
(2) When the compilers catch up with the proposed standard, i will be
local to the loop, which is probably what the original poster wanted.

--Tim Smith
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void function()

  {

  char * st = "Test";
  char * s;

  for (int i = 0,s = st; i < 2; ++i)
    {
    }

  }

All my C++ compilers on Windows NT, Borland C++ 5.02, Borland C++
Builder 1.0, Microsoft C++ 5.0, Symantec C++ 7.5, and Watcom C++ 11.0,
give an error message when compiling this code, all on the line of the
"for" loop. Am I really saying here that the variable "s" is of type
integer, as all the compilers claim, or am I just trying to initialize
my variable "s", which is a char * to another char *, as I believe. If
the compilers are right and I am wrong, how do I initialize my "char *
s" in the first part of the "for" loop ? What does the standard say
about this ? Have I found an undefined area of the standard here ?
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Edward Diener <eddielee@abraxis.com> writes:

>  char * st = "Test";
>  char * s;
>
>  for (int i = 0,s = st; i < 2; ++i)
...
>All my C++ compilers on Windows NT, Borland C++ 5.02, Borland C++
>Builder 1.0, Microsoft C++ 5.0, Symantec C++ 7.5, and Watcom C++ 11.0,
>give an error message when compiling this code, all on the line of the
>"for" loop. Am I really saying here that the variable "s" is of type
>integer, as all the compilers claim, or am I just trying to initialize
>my variable "s", which is a char * to another char *, as I believe.

The compilers are right.

>If the compilers are right and I am wrong, how do I initialize my "char *
>s" in the first part of the "for" loop ?

One way is to move the declaration of `i' to before the for loop:

   char * st = "Test";
   char * s;
   int i;
   for (i = 0, s = st; i < 2; ++i)

>What does the standard say about this ?

The grammar for a `for' statement says that the first part is either
an expression-statement or a simple-declaration.
`int i = 0, s = st' is not an expression-statement, so it must be
a simple-declaration.  When you follow the details, you'll see that
it declares `s' to be an int.

>Have I found an undefined area of the standard here ?

No.

--
Fergus Henderson <fjh@cs.mu.oz.au>   |  "I have always known that the pursuit
WWW: <http://www.cs.mu.oz.au/~fjh>   |  of excellence is a lethal habit"
PGP: finger fjh@128.250.37.3         |     -- the last words of T. S. Garp.
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Edward Diener wrote:
 >
 > void function()
 >
 >   {
 >
 >   char * st = "Test";
 >   char * s;
 >
 >   for (int i = 0,s = st; i < 2; ++i)
 >     {
 >     }
 >
 >   }
 >
 > All my C++ compilers on Windows NT, Borland C++ 5.02, Borland C++
 > Builder 1.0, Microsoft C++ 5.0, Symantec C++ 7.5, and Watcom C++ 11.0,
 > give an error message when compiling this code, all on the line of the
 > "for" loop.

I think you should write:

const char* st = "Test";
const char* s;

for (int i = (s = st, 0); i < 2; ++i);

--

Valentin Bonnard                mailto:bonnardv@pratique.fr
info about C++/a propos du C++: http://www.pratique.fr/~bonnardv/
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Edward Diener wrote:
>
> void function()
>
>   {
>
>   char * st = "Test";
>   char * s;
>
>   for (int i = 0,s = st; i < 2; ++i)
>     {
>     }
>
>   }
>
> All my C++ compilers on Windows NT, Borland C++ 5.02, Borland C++
> Builder 1.0, Microsoft C++ 5.0, Symantec C++ 7.5, and Watcom C++ 11.0,
> give an error message when compiling this code, all on the line of the
> "for" loop. Am I really saying here that the variable "s" is of type
> integer, as all the compilers claim, or am I just trying to initialize
> my variable "s", which is a char * to another char *, as I believe. If
> the compilers are right and I am wrong, how do I initialize my "char *
> s" in the first part of the "for" loop ? What does the standard say
> about this ? Have I found an undefined area of the standard here ?

The compilers are right...

The declaration/initialization
 int i = 0, s = st;
(say, at top level) declares two integers and initializes the
second. The comma here separates the two names that are introduced,
and the '=' initializes s.

We are used to writing
 for (i=0,s=st;i<2;i++)
but 'i=0,s=st' is just one statement.
(Actually one expression, consisting of two subexpressions connected
by the *comma operator*, and those two expressions happen to be
assignments).

In other words, the first part of the for (the for-init-statement
in the draft standard grammar) is just a C++ statement, so if
you can write it at top level, you can put it there.

I don't think there is a way to get a declaration and an assignment
in just a single statement, (which is what you are looking for), so
I would put one of them outside the for.

(You can always put the for in a separate scope if you want to.)

Hope this helps.

Manos
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Valentin Bonnard <bonnardv@pratique.fr> writes:

 |> Edward Diener wrote:
 |>  >
 |>  > void function()
 |>  >
 |>  >   {
 |>  >
 |>  >   char * st = "Test";
 |>  >   char * s;
 |>  >
 |>  >   for (int i = 0,s = st; i < 2; ++i)
 |>  >     {
 |>  >     }
 |>  >
 |>  >   }
 |>  >
 |>  > All my C++ compilers on Windows NT, Borland C++ 5.02, Borland C++
 |>  > Builder 1.0, Microsoft C++ 5.0, Symantec C++ 7.5, and Watcom C++ 11.0,
 |>  > give an error message when compiling this code, all on the line of the
 |>  > "for" loop.
 |>
 |> I think you should write:
 |>
 |> const char* st = "Test";
 |> const char* s;
 |>
 |> for (int i = (s = st, 0); i < 2; ++i);

I was actually going to propose the same thing, but with a smiley.  You
don't really want people to write code like that, do you?

And while I'm at it, I suppose that the semi-colon on the same line as
the for is a typo.  Or... let's indent the following line as well --
keep the maintainance programmer guessing, that's my motto.

--
James Kanze    +33 (0)1 39 23 84 71    mailto: kanze@gabi-soft.fr
GABI Software, 22 rue Jacques-Lemercier, 78000 Versailles, France
        I'm looking for a job -- Je recherche du travail
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Edward Diener wrote in message <3442B366.CCA53D4@abraxis.com>...

>  char * st = "Test";
>  char * s;
>
>  for (int i = 0,s = st; i < 2; ++i)

>All my C++ compilers on Windows NT, Borland C++ 5.02, Borland C++
>Builder 1.0, Microsoft C++ 5.0, Symantec C++ 7.5, and Watcom C++ 11.0,
>give an error message when compiling this code, all on the line of the
>"for" loop. Am I really saying here that the variable "s" is of type
>integer, as all the compilers claim, or am I just trying to initialize

Unfortunately, you've discovered a sort of precedence issue that the
standard doesn't do anything about. You are allowed to write this code,
right?

int i = 0, s = 4;

Certainly, you would not expect your C++ compiler to instantiate 'i' as an
int, then to treat 's' as if it already existed somewhere else, would you?
What if you wrote this:

int s;
int i = 0, s = 4;

Wouldn't you expect your compiler to tell you on the second line that 's' is
already defined elsewhere? If so, then why does an error here surprise you?

int s;
for (int i = 0, s = 4; ... )

The fact is, when you start a statement with a type and a previously unknown
identifier like this, you've just committed yourself to a declaration. You
must then follow the rules of a declaration, as opposed to a statement.

John Calcote
Directory Services
Novell, Inc.
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