A trick with if-else

[Piyush Agarwal]

void main
{
int x;
if(x)
printf("Hello");
else
printf("World");
}
What value can be given to x such that the output is "Hello
World"?

[Vladimir Oka]

Piyush Agarwal wrote:

void main
{
int x;
if(x)
printf("Hello");
else
printf("World");
}
What value can be given to x such that the output is "Hello
World"?

I think you misrepresented the trick question.

With `x` an `int` it will never work.

However, if you `#define x` appropriatelly, you can get the desired
effect. E.g.:

#define x (!printf("Hello "))

will do the trick. Obviously, once you correct your code to something
that actually resembles C:

#include <stdio.h>

#define x (!printf("Hello, "))

int main(void)
{
if(x)
printf("Hello");
else
printf("World");

printf("\n");

return 0;
}

[Chris Dollin]

Piyush Agarwal wrote:

void main
{
`main` is a function that returns `int`, not a non-function
of type `void` and value `bother, there was a syntax error`.
int x;
if(x)
printf("Hello");
else
printf("World");
}
What value can be given to x such that the output is "Hello
World"?

There isn't one.

If you didn't mean /value/, but /initialiser/, then easy-peasy.

--
Chris "but the if becomes irrelevant" Dollin
"People are part of the design. It's dangerous to forget that." /Star Cops/

[Richard Heathfield]

Piyush Agarwal said:

void main
{
int x;
if(x)
printf("Hello");
else
printf("World");
}
What value can be given to x such that the output is "Hello
World"?

The output of the program is undefined for no fewer than three different
reasons. So it might well say "Hello World" as written. Or, of course, it
might not.

Until you understand what the three reasons are, I recommend that you spend
less time with puzzle questions and more time with a good C book.

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

[Kenneth Brody]

Piyush Agarwal wrote:

void main
{
int x;
if(x)
printf("Hello");
else
printf("World");
}
What value can be given to x such that the output is "Hello
World"?

Given that you're on Google, why not just search the c.l.c archives for
the thread on the almost exact same question from a few weeks ago?

Perhaps you should give us your professor's name, as I'm sure we'd all
like to know who gives out such homework assignments.

Of course, given your syntax error on "void main" (and numerous other
things), your version of the "problem" is unsolvable.

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

[John Devereux]

Chris Dollin <ch**********@hp.com> writes:

Piyush Agarwal wrote:

void main
{

`main` is a function that returns `int`, not a non-function
of type `void` and value `bother, there was a syntax error`.

int x;
if(x)
printf("Hello");
else
printf("World");
}
What value can be given to x such that the output is "Hello
World"?

There isn't one.

If you didn't mean /value/, but /initialiser/, then easy-peasy.

OK, I'll bite.... What initialiser?

--

John Devereux

[Suman]

Vladimir Oka wrote:

Piyush Agarwal wrote:

[ snip code with UB ]

What value can be given to x such that the output is "Hello
World"?

I think you misrepresented the trick question.

With `x` an `int` it will never work.

#include <stdio.h>

int main(void)
{
int x = 0;
if ( (printf("Hello, "), x) )
printf("Hello");
else
printf("World\n");
return 0;
}

[Vladimir Oka]

John Devereux wrote:

Chris Dollin <ch**********@hp.com> writes:

Piyush Agarwal wrote:

void main
{

`main` is a function that returns `int`, not a non-function
of type `void` and value `bother, there was a syntax error`.

int x;
if(x)
printf("Hello");
else
printf("World");
}
What value can be given to x such that the output is "Hello
World"?

There isn't one.

If you didn't mean /value/, but /initialiser/, then easy-peasy.

OK, I'll bite.... What initialiser?

You can do:

int x = !printf("Hello ");

[The "solution" I overlooked in my earlier post.]

[Vladimir Oka]

Suman wrote:

Vladimir Oka wrote:

Piyush Agarwal wrote:

[ snip code with UB ]

What value can be given to x such that the output is "Hello
World"?

I think you misrepresented the trick question.

With `x` an `int` it will never work.

#include <stdio.h>

int main(void)
{
int x = 0;
if ( (printf("Hello, "), x) )
printf("Hello");
else
printf("World\n");
return 0;
}

I don't think you were allowed to change the `if` statement. Have a
look at my other post as well.

[John Devereux]

"Vladimir Oka" <no****@btopenworld.com> writes:

John Devereux wrote:

Chris Dollin <ch**********@hp.com> writes:

> Piyush Agarwal wrote:
>
>> void main
>> {
>
> `main` is a function that returns `int`, not a non-function
> of type `void` and value `bother, there was a syntax error`.
>
>> int x;
>> if(x)
>> printf("Hello");
>> else
>> printf("World");
>> }
>> What value can be given to x such that the output is "Hello
>> World"?
>
> There isn't one.
>
> If you didn't mean /value/, but /initialiser/, then easy-peasy.

OK, I'll bite.... What initialiser?

You can do:

int x = !printf("Hello ");

[The "solution" I overlooked in my earlier post.]

Aha! :)

--

John Devereux

[Suman]

Vladimir Oka wrote:

Suman wrote:

Vladimir Oka wrote:

Piyush Agarwal wrote:

[ snip code with UB ]

> What value can be given to x such that the output is "Hello
> World"?

I think you misrepresented the trick question.

With `x` an `int` it will never work.

#include <stdio.h>

int main(void)
{
int x = 0;
if ( (printf("Hello, "), x) )
printf("Hello");
else
printf("World\n");
return 0;
}

I don't think you were allowed to change the `if` statement. Have a
look at my other post as well.

Show me where this constraint was mentioned ;)
Also your _other_ post came in a minute too late, I'd
already posted my reply before it came to being.

[Vladimir Oka]

Suman wrote:

Vladimir Oka wrote:

Suman wrote:

Vladimir Oka wrote:
> Piyush Agarwal wrote:

[ snip code with UB ]

> > What value can be given to x such that the output is "Hello
> > World"?
>
> I think you misrepresented the trick question.
>
> With `x` an `int` it will never work.

#include <stdio.h>

int main(void)
{
int x = 0;
if ( (printf("Hello, "), x) )
printf("Hello");
else
printf("World\n");
return 0;
}

I don't think you were allowed to change the `if` statement. Have a
look at my other post as well.

Show me where this constraint was mentioned ;)
Also your _other_ post came in a minute too late, I'd
already posted my reply before it came to being.

Well, it wasn't mentioned in so many words. I thought it was implied.
Still, you could even do someting like:

if ( x = !printf("Hello ") )

or even better:

if ( x = (printf("Hello ") != 6) )

;-)

[Chris Dollin]

Vladimir Oka wrote:

John Devereux wrote:

Chris Dollin <ch**********@hp.com> writes:

> Piyush Agarwal wrote:
>
>> void main
>> {
>
> `main` is a function that returns `int`, not a non-function
> of type `void` and value `bother, there was a syntax error`.
>
>> int x;
>> if(x)
>> printf("Hello");
>> else
>> printf("World");
>> }
>> What value can be given to x such that the output is "Hello
>> World"?
>
> There isn't one.
>
> If you didn't mean /value/, but /initialiser/, then easy-peasy.

OK, I'll bite.... What initialiser?

You can do:

int x = !printf("Hello ");

[The "solution" I overlooked in my earlier post.]

S'not portable - there's no final newline after the World.

int x = (printf( "Hello, World\n" ), exit( 0 ), 17);

will do fine.

--
Chris "Eyeball" Dollin
"People are part of the design. It's dangerous to forget that." /Star Cops/

[Chris Dollin]

Suman wrote:

Vladimir Oka wrote:

Suman wrote:

> Vladimir Oka wrote:
> > Piyush Agarwal wrote:
>
> [ snip code with UB ]
>
> > > What value can be given to x such that the output is "Hello
> > > World"?
> >
> > I think you misrepresented the trick question.
> >
> > With `x` an `int` it will never work.
>
> #include <stdio.h>
>
> int main(void)
> {
> int x = 0;
> if ( (printf("Hello, "), x) )
> printf("Hello");
> else
> printf("World\n");
> return 0;
> }

I don't think you were allowed to change the `if` statement. Have a
look at my other post as well.

Show me where this constraint was mentioned ;)

Oh, in /that/ case:

int main() { printf( "Hello, World\n" ); }

will do.

--
Chris "Eyeball" Dollin
"People are part of the design. It's dangerous to forget that." /Star Cops/

[Vladimir Oka]

Chris Dollin wrote:

Vladimir Oka wrote:

John Devereux wrote:

Chris Dollin <ch**********@hp.com> writes:

> Piyush Agarwal wrote:
>
>> void main
>> {
>
> `main` is a function that returns `int`, not a non-function
> of type `void` and value `bother, there was a syntax error`.
>
>> int x;
>> if(x)
>> printf("Hello");
>> else
>> printf("World");
>> }
>> What value can be given to x such that the output is "Hello
>> World"?
>
> There isn't one.
>
> If you didn't mean /value/, but /initialiser/, then easy-peasy.

OK, I'll bite.... What initialiser?

You can do:

int x = !printf("Hello ");

[The "solution" I overlooked in my earlier post.]

S'not portable - there's no final newline after the World.

int x = (printf( "Hello, World\n" ), exit( 0 ), 17);

will do fine.

Yep. Using 42 instead of 17 would have been even better. ;-)

I was however building on the code I supplied in my original reply to
the OP (which did include the terminating '\n').

[Chris Dollin]

Vladimir Oka wrote:

Chris Dollin wrote:

S'not portable - there's no final newline after the World.

int x = (printf( "Hello, World\n" ), exit( 0 ), 17);

will do fine.

Yep. Using 42 instead of 17 would have been even better. ;-)

No, it wouldn't - I didn't wish to allude to tHGttG. Instead I alluded
to something else.

--
Chris "Veraly, these references are a drag." Dollin
"People are part of the design. It's dangerous to forget that." /Star Cops/

[Vladimir Oka]

Chris Dollin wrote:

Vladimir Oka wrote:

Chris Dollin wrote:

S'not portable - there's no final newline after the World.

int x = (printf( "Hello, World\n" ), exit( 0 ), 17);

will do fine.

Yep. Using 42 instead of 17 would have been even better. ;-)

No, it wouldn't - I didn't wish to allude to tHGttG. Instead I alluded
to something else.

You got me there. I dont get the allusion.

[17 *is*, more often than not, my staple "random" value, but I doubt
you know me that well. ;-)]

[Keith Thompson]

Richard Heathfield <in*****@invalid.invalid> writes:

Piyush Agarwal said:

void main
{
int x;
if(x)
printf("Hello");
else
printf("World");
}
What value can be given to x such that the output is "Hello
World"?

The output of the program is undefined for no fewer than three different
reasons. So it might well say "Hello World" as written. Or, of course, it
might not.

Until you understand what the three reasons are, I recommend that you spend
less time with puzzle questions and more time with a good C book.

I see four reasons (one of which is unlikely to cause mere undefined
behavior).

--
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.

[Martin Ambuhl]

Piyush Agarwal wrote:

void main ^^^^ dead akready: main returns an int {
int x;
if(x) ^^^ dead again: x is not initialized printf("Hello"); ^^^^^^ dead again; a variadic function with no declaration in
scope else
printf("World"); For pre-C99 compilers (and with any decent coding standards even
with C99), dead again without a returned value. }
What value can be given to x such that the output is "Hello
World"?

We answered this already, several times over. Please check the archives
before posting. Although it is not relevant to your question (but is
to your horrid code), check the FAQ before posting as well.

[Richard Heathfield]

Keith Thompson said:

I see four reasons (one of which is unlikely to cause mere undefined
behavior).

Believe it or not, the syntax error completely passed me by.

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

[Kenneth Brody]

Suman wrote:

Vladimir Oka wrote:

Suman wrote:

Vladimir Oka wrote:
> Piyush Agarwal wrote:

[ snip code with UB ]

> > What value can be given to x such that the output is "Hello
> > World"?
>
> I think you misrepresented the trick question.
>
> With `x` an `int` it will never work.

[... snip code with rewritten main() ...]
I don't think you were allowed to change the `if` statement. Have a
look at my other post as well.

Show me where this constraint was mentioned ;)

The original post said:

What value can be given to x such that the output is "Hello World"?

All you're allowed to do is give x a value.

If you're allowed to modify the code, why not just:

#include <stdio.h>
int main(void)
{
printf("Hello World\n");
}

[...]

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

[Kenneth Brody]

Vladimir Oka wrote:

Chris Dollin wrote:

Vladimir Oka wrote:

Chris Dollin wrote:
> S'not portable - there's no final newline after the World.
>
> int x = (printf( "Hello, World\n" ), exit( 0 ), 17);
>
> will do fine.

Yep. Using 42 instead of 17 would have been even better. ;-)

No, it wouldn't - I didn't wish to allude to tHGttG. Instead I alluded
to something else.

You got me there. I dont get the allusion.

[17 *is*, more often than not, my staple "random" value, but I doubt
you know me that well. ;-)]

But everyone knows that 17 is the "least random" number. Use 37 instead.

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

[Vladimir Oka]

Kenneth Brody opined:

Vladimir Oka wrote:

Chris Dollin wrote:

> Vladimir Oka wrote:
>
> > Chris Dollin wrote:
> >> S'not portable - there's no final newline after the World.
> >>
> >> int x = (printf( "Hello, World\n" ), exit( 0 ), 17);
> >>
> >> will do fine.
> >
> > Yep. Using 42 instead of 17 would have been even better. ;-)
>
> No, it wouldn't - I didn't wish to allude to tHGttG. Instead I
> alluded to something else.

You got me there. I dont get the allusion.

[17 *is*, more often than not, my staple "random" value, but I doubt
you know me that well. ;-)]

But everyone knows that 17 is the "least random" number. Use 37
instead.

Well, occasionally I use 57 instead.

(Probably has something to do with how it sounds in my native language.
Interestingly, although I fully think in English when I use it, I
still always think numbers in my native language. I don't understand
it, really.)

--
Killing is stupid; useless!
-- McCoy, "A Private Little War", stardate 4211.8

<http://clc-wiki.net/wiki/Introduction_to_comp.lang.c>

[pete]

Vladimir Oka wrote:

Well, occasionally I use 57 instead.

(Probably has something to do with how it sounds in
my native language.
Interestingly, although I fully think in English when I use it, I
still always think numbers in my native language. I don't understand
it, really.)

Results 1 - 10 of about 76 for "57 card carrying communists".

Results 1 - 10 of about 176,000 for "57 varieties".

http://www.snopes.com/business/hidden/heinz57.asp

--
pete

[Chris Dollin]

Vladimir Oka wrote:

Chris Dollin wrote:

Vladimir Oka wrote:

> Chris Dollin wrote:
>> S'not portable - there's no final newline after the World.
>>
>> int x = (printf( "Hello, World\n" ), exit( 0 ), 17);
>>
>> will do fine.
>
> Yep. Using 42 instead of 17 would have been even better. ;-)

No, it wouldn't - I didn't wish to allude to tHGttG. Instead I alluded
to something else.

You got me there. I dont get the allusion.

There was of course a clue in my signature. Don't worry - the allusion is
obscure; I just wanted a change.

--
Chris "anyway, I don't paint." Dollin
"Everyone generalises from a single example. I know I do." - Vlad Taltos