if (--n==n)

[Raman]

Hi All,

I have small fragment of code ...
main()
{
int n=10;

if(--n==n)
{
printf("\n Pre");
}
if(n--==n)
{
printf(" Post");
}

}//main
What shall be the output of the above code.

Thanks
Raman Chalotra

[Gerr]

Raman <ra***********@gmail.comwrote:

Hi All,

I have small fragment of code ...
main()
{
int n=10;

if(--n==n)
{
printf("\n Pre");
}
if(n--==n)
{
printf(" Post");
}

}//main
What shall be the output of the above code.

Undefined behaviour, see section 3 of the c.l.c. FAQ:

http://docs.mandragor.org/files/Prog.../C-faq/s3.html

[santosh]

Raman wrote:

Hi All,

I have small fragment of code ...
main()
{
int n=10;

if(--n==n)
{
printf("\n Pre");
}
if(n--==n)
{
printf(" Post");
}

}//main
What shall be the output of the above code.

It'll set fire to your computer.

You're invoking undefined behaviour in several places. See link below:
<http://c-faq.com/expr/index.html>

[Richard Heathfield]

santosh said:

Raman wrote:

>>
What shall be the output of the above code.

It'll set fire to your computer.

The Standard does not actually guarantee this.

--
Richard Heathfield
"Usenet is a strange place" - dmr 29/7/1999
http://www.cpax.org.uk
email: rjh at the above domain, - www.

[mark_bluemel]

Raman wrote:

I have small fragment of code ...

Thank you for posting a complete program...

main()

We prefer "int main(void)", but it's only a stylistic thing, really.

{
int n=10;

if(--n==n)
{
printf("\n Pre");
}
if(n--==n)
{
printf(" Post");
}

}//main

Please don't use "//" comments - they're not in the standard that most
of us are working with, and may upset our compilers.

What shall be the output of the above code.

The standard explicitly says this yields undefined behaviour - demons
flying out of your nose or your computer catching fire are unlikely,
but allowed by the standard. It's not guaranteed that this program will
behave consistently on different platforms, or compiled by different
compilers (or with different compiler optimisation).

Empirically this produced "Pre" on my linux workstation, compiled with
some version of GCC. On an AIX server using Xlc (again version
unspecified) I got "Pre Post".

Why do you ask?

[Raman]

Hi,
I wanted to know what you tell( I was not sure ), that it may produce
post as well..
Thanks
Raman Chalotra

ma**********@pobox.com wrote:

Raman wrote:

I have small fragment of code ...

Thank you for posting a complete program...

main()

We prefer "int main(void)", but it's only a stylistic thing, really.

{
int n=10;

if(--n==n)
{
printf("\n Pre");
}
if(n--==n)
{
printf(" Post");
}

}//main

Please don't use "//" comments - they're not in the standard that most
of us are working with, and may upset our compilers.

What shall be the output of the above code.

The standard explicitly says this yields undefined behaviour - demons
flying out of your nose or your computer catching fire are unlikely,
but allowed by the standard. It's not guaranteed that this program will
behave consistently on different platforms, or compiled by different
compilers (or with different compiler optimisation).

Empirically this produced "Pre" on my linux workstation, compiled with
some version of GCC. On an AIX server using Xlc (again version
unspecified) I got "Pre Post".

Why do you ask?

[Ico]

Raman <ra***********@gmail.comwrote:

Hi,
I wanted to know what you tell( I was not sure ), that it may produce
post as well..

But do you now understand *why* it can produce 'post' as well ?

--
:wq
^X^Cy^K^X^C^C^C^C

[Flash Gordon]

ma**********@pobox.com wrote, On 22/01/07 11:12:

Raman wrote:

>I have small fragment of code ...

Thank you for posting a complete program...

>main()

We prefer "int main(void)", but it's only a stylistic thing, really.

<snip>

>}//main

Please don't use "//" comments - they're not in the standard that most
of us are working with, and may upset our compilers.

Actually whether one uses "main()" is not purely stylistic because it is
not valid in the C standard that allows "//" style comments. So any
program such as Raman's that uses "main()" and "//" style comments is
not valid C according to *any* standard.
--
Flash Gordon

[Ben Pfaff]

Flash Gordon <sp**@flash-gordon.me.ukwrites:

Actually whether one uses "main()" is not purely stylistic
because it is not valid in the C standard that allows "//"
style comments.

Writing "main()" is fine in C99. It's the absence of an explicit
return type (also seen in the example in question) that C99
disallows.
--
"What is appropriate for the master is not appropriate for the novice.
You must understand the Tao before transcending structure."
--The Tao of Programming

[Default User]

Raman wrote:

Hi,

Please don't top-post. Your replies belong following or interspersed
with properly trimmed quotes. See the majority of other posts in the
newsgroup, or:
<http://www.caliburn.nl/topposting.html>

[Flash Gordon]

Ben Pfaff wrote, On 22/01/07 17:18:

Flash Gordon <sp**@flash-gordon.me.ukwrites:

>Actually whether one uses "main()" is not purely stylistic
because it is not valid in the C standard that allows "//"
style comments.

Writing "main()" is fine in C99. It's the absence of an explicit
return type (also seen in the example in question) that C99
disallows.

The context was someone saying to use "int main(void)" rather than
"main()". Admittedly I could have made it clear it was the lack of
return type that was the problem in C99.
--
Flash Gordon

[Kenny McCormack]

In article <51*************@mid.individual.net>,
Default Loser <de************@yahoo.comwrote:
....

>Please don't top-post. Your replies belong following or interspersed
with properly trimmed quotes. See the majority of other posts in the
newsgroup, or:
<http://www.caliburn.nl/topposting.html>

Get a life!