wrong output

[Vaibhav87]

the code is
#define PROD(x) x+x
main()
{
int i=3,j;
j=PROD(i+1);
printf("%d", j);
}

pls tell me the output and how it is so?

[jacob navia]

Va*******@gmail.com a écrit :

the code is
#define PROD(x) x+x
main()
{
int i=3,j;
j=PROD(i+1);
printf("%d", j);
}

pls tell me the output and how it is so?

Do not cheat. Do your own homework.

[Roland Csaszar]

Va*******@gmail.com wrote:

the code is
#define PROD(x) x+x

Seems like a funny definition of 'product' :)

--
Roland Csaszar ----------- \\\ /// -------------- [phone]
Software Development ------ \\\ /// ----------- http://www.knapp.com
KNAPP Logistics Automation - \\V// - mailto:ro************@knapp.com

[jacob navia]

Roland Csaszar a écrit :

Va*******@gmail.com wrote:

>>the code is
#define PROD(x) x+x

Seems like a funny definition of 'product' :)

yes, he can't even copy the homework correctly!

[lovecreatesbea...]

jacob navia wrote:

Roland Csaszar a écrit :

Va*******@gmail.com wrote:

>the code is
#define PROD(x) x+x

Seems like a funny definition of 'product' :)

yes, he can't even copy the homework correctly!

The code in the original post compiles and works.

One guy gives some programming truths as follows:
If it compiles, it works.
If it compiles, it's correct.
...

The original code complies with those truths listed on that guy's
homepage. That personal homepage (perhaps includes those truths) was
recommended by the creator of Linux, Linus Torvalds.

[Christopher Benson-Manica]

[e-mail] <lo***************@gmail.comwrote:

The code in the original post compiles and works.

If by "works" you mean "didn't happen to launch nuclear missiles that
time" then sure. It failed to include a prototype for printf() and
thus invoked UB, in addition to failing to return a value from main.

One guy gives some programming truths as follows:
If it compiles, it works.
If it compiles, it's correct.

Nonsense. Otherwise I could write an operating system in one line of
C code as long as it compiled:

int main(void) {return 0;}

--
C. Benson Manica | I *should* know what I'm talking about - if I
cbmanica(at)gmail.com | don't, I need to know. Flames welcome.

[Fred Kleinschmidt]

"Christopher Benson-Manica" <at***@ukato.freeshell.orgwrote in message
news:ed**********@chessie.cirr.com...

[e-mail] <lo***************@gmail.comwrote:

>The code in the original post compiles and works.

If by "works" you mean "didn't happen to launch nuclear missiles that
time" then sure. It failed to include a prototype for printf() and
thus invoked UB, in addition to failing to return a value from main.

>One guy gives some programming truths as follows:
If it compiles, it works.
If it compiles, it's correct.

Nonsense. Otherwise I could write an operating system in one line of
C code as long as it compiled:

int main(void) {return 0;}

Well, that compiles. And it works.
Maybe not the way you WANTED it to work, but it does "work".

--
Fred L. Kleinschmidt
Boeing Associate Technical Fellow
Technical Architect, Software Reuse Project

>
--
C. Benson Manica | I *should* know what I'm talking about - if I
cbmanica(at)gmail.com | don't, I need to know. Flames welcome.

[Mark McIntyre]

On 7 Sep 2006 05:49:50 -0700, in comp.lang.c , "Va*******@gmail.com"
<Va*******@gmail.comwrote:

>the code is
#define PROD(x) x+x
main()
{
int i=3,j;
j=PROD(i+1);
printf("%d", j);
}

pls tell me the output and how it is so?

Macros are quite literally substituted into the code. So you can by
hand rewrite this code to replace PROD with the actual code.

In this case if PROD were defined as
#define PROD(x) x*x
(which would be more logical....) then you will get an interesting
result.
--
Mark McIntyre

"Debugging is twice as hard as writing the code in the first place.
Therefore, if you write the code as cleverly as possible, you are,
by definition, not smart enough to debug it."
--Brian Kernighan

[Joe Wright]

Va*******@gmail.com wrote:

the code is
#define PROD(x) x+x
main()
{
int i=3,j;
j=PROD(i+1);
printf("%d", j);
}

pls tell me the output and how it is so?

I've taken the liberty to modify your snippet into a C program.

#include <stdio.h>
#define PROD(x) x+x
int main(void)
{
int i = 3, j;
j = PROD(i + 1);
printf("%d\n", j);
return 0;
}

I get 8 as I expect. What do you get? What do you expect?

--
Joe Wright
"Everything should be made as simple as possible, but not simpler."
--- Albert Einstein ---

[Joe Wright]

Mark McIntyre wrote:

On 7 Sep 2006 05:49:50 -0700, in comp.lang.c , "Va*******@gmail.com"
<Va*******@gmail.comwrote:

>the code is
#define PROD(x) x+x
main()
{
int i=3,j;
j=PROD(i+1);
printf("%d", j);
}

pls tell me the output and how it is so?

Macros are quite literally substituted into the code. So you can by
hand rewrite this code to replace PROD with the actual code.

In this case if PROD were defined as
#define PROD(x) x*x
(which would be more logical....) then you will get an interesting
result.

Indeed. (3+1+3+1) is 8 as expected. (3+1*3+1) is 7. Huh?
So that's what parentheses are for? ((3+1)*(3+1)) is 16.

--
Joe Wright
"Everything should be made as simple as possible, but not simpler."
--- Albert Einstein ---

[Mark McIntyre]

On Thu, 07 Sep 2006 21:19:19 -0400, in comp.lang.c , Joe Wright
<jo********@comcast.netwrote:

>Mark McIntyre wrote:

>In this case if PROD were defined as
#define PROD(x) x*x
(which would be more logical....) then you will get an interesting
result.

Indeed. (3+1+3+1) is 8 as expected. (3+1*3+1) is 7. Huh?
So that's what parentheses are for? ((3+1)*(3+1)) is 16.

I'm not sure if you're trying to state the bleedin' obvious, or if
you've totally missed the point of my post, or if you think I'm
missing something. I'm not.
--
Mark McIntyre

"Debugging is twice as hard as writing the code in the first place.
Therefore, if you write the code as cleverly as possible, you are,
by definition, not smart enough to debug it."
--Brian Kernighan

[Joe Wright]

Mark McIntyre wrote:

On Thu, 07 Sep 2006 21:19:19 -0400, in comp.lang.c , Joe Wright
<jo********@comcast.netwrote:

>Mark McIntyre wrote:

>>In this case if PROD were defined as
#define PROD(x) x*x
(which would be more logical....) then you will get an interesting
result.

Indeed. (3+1+3+1) is 8 as expected. (3+1*3+1) is 7. Huh?
So that's what parentheses are for? ((3+1)*(3+1)) is 16.

I'm not sure if you're trying to state the bleedin' obvious, or if
you've totally missed the point of my post, or if you think I'm
missing something. I'm not.

Just stating the obvious for others. You hardly ever miss anything.

--
Joe Wright
"Everything should be made as simple as possible, but not simpler."
--- Albert Einstein ---

[Vaibhav87]

sorry it's my mistake the macro was
#define PROD (x) x*x
now pls explain me i've stuck on that.

[Kenneth Brody]

"Va*******@gmail.com" wrote:

>
sorry it's my mistake the macro was
#define PROD (x) x*x

This is why everyone here will tell you "cut and paste the actual code,
rather than (mis)typing it into your post".

now pls explain me i've stuck on that.

>From your original post:

[...]
int i=3,j;
j=PROD(i+1);
[...]

What do you expect this line to do? Pretend you're the C preprocessor.
What does this line look like after expanding the macro?

Now, what do you expect the output to be? What output do you get when
you compile and run the program?

--
+-------------------------+--------------------+-----------------------+
| Kenneth J. Brody | www.hvcomputer.com | #include |
| kenbrody/at\spamcop.net | www.fptech.com | <std_disclaimer.h|
+-------------------------+--------------------+-----------------------+
Don't e-mail me at: <mailto:Th*************@gmail.com>

[Keith Thompson]

"Va*******@gmail.com" <Va*******@gmail.comwrites:

sorry it's my mistake the macro was
#define PROD (x) x*x
now pls explain me i've stuck on that.

Provide context when posting a followup. Google does this for you;
apparently you're deliberately deleting the context. Read
<http://cfaj.freeshell.org/google/>.

Make some effort to write proper English. Don't use silly little
abbreviations like "pls" for "please". Capitalize the first word of
each sentence, and the word "I". We don't care much about the
occasional spelling or grammatical error, especially if English isn't
your first language, but make some effort to spell things out; this is
a technical discussion forum, not some kind of chat room.

The comp.lang.c FAQ is at <http://www.c-faq.com/>. You've asked
question 10.1.

--
Keith Thompson (The_Other_Keith) ks***@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.

[Mark McIntyre]

On 13 Sep 2006 06:46:08 -0700, in comp.lang.c , "Va*******@gmail.com"
<Va*******@gmail.comwrote:

>sorry it's my mistake the macro was
#define PROD (x) x*x
now pls explain me i've stuck on that.

what is PROD(4+4)?

Write it down by expanding the macro manually, and you will see a
problem.
--
Mark McIntyre

"Debugging is twice as hard as writing the code in the first place.
Therefore, if you write the code as cleverly as possible, you are,
by definition, not smart enough to debug it."
--Brian Kernighan