expression evaluation : help!

[manan.kathuria@gmail.com]

hi all ,
the expression in question is

++i&&++j||++k

most sources say that since the result of the || operation is decided
by the LHS itself , the right side is not computed

my point of thinking is that since the unary operator has higher
precedence than || , it will be evaluated before || in any
case........... where am im going wrong

thanks in anticipation

Manan

[Joona I Palaste]

Re: expression evaluation : help!

manan.kathuria@ gmail.com scribbled the following:[color=blue]
> hi all ,
> the expression in question is[/color]
[color=blue]
> ++i&&++j||++k[/color]
[color=blue]
> most sources say that since the result of the || operation is decided
> by the LHS itself , the right side is not computed[/color]
[color=blue]
> my point of thinking is that since the unary operator has higher
> precedence than || , it will be evaluated before || in any
> case........... where am im going wrong[/color]

Where you're going wrong is thinking precedence and order of evaluation
are the same thing. They're nothing of the sort. Precedence dictates how
a string of C tokens is compiled into an expression. Order of evaluation
dictates how that expression is evaluated at run-time.

--
/-- Joona Palaste (palaste@cc.hel sinki.fi) ------------- Finland --------\
\-------------------------------------------------------- rules! --------/
"C++. C++ run. Run, ++, run."
- JIPsoft

[Michael Mair]

Re: expression evaluation : help!

manan.kathuria@ gmail.com wrote:[color=blue]
> hi all ,
> the expression in question is
>
> ++i&&++j||++k
>
> most sources say that since the result of the || operation is decided
> by the LHS itself , the right side is not computed
>
> my point of thinking is that since the unary operator has higher
> precedence than || , it will be evaluated before || in any
> case........... where am im going wrong[/color]

See FAQ 3.5 and 3.8, best read the whole section 3:

http://www.eskimo.com/~scs/C-faq/s3.html

Note: The ASCII text version posted here by Steve Summit is
more complete/up to date than the above HTML version but can
be obtained following the links from

http://www.eskimo.com/~scs/C-faq/top.html

Cheers
Michael
--
E-Mail: Mine is an /at/ gmx /dot/ de address.

[Joona I Palaste]

Re: expression evaluation : help!

Michael Mair <Michael.Mair@i nvalid.invalid> scribbled the following:[color=blue]
> manan.kathuria@ gmail.com wrote:[color=green]
>> hi all ,
>> the expression in question is
>>
>> ++i&&++j||++k
>>
>> most sources say that since the result of the || operation is decided
>> by the LHS itself , the right side is not computed
>>
>> my point of thinking is that since the unary operator has higher
>> precedence than || , it will be evaluated before || in any
>> case........... where am im going wrong[/color][/color]
[color=blue]
> See FAQ 3.5 and 3.8, best read the whole section 3:
> http://www.eskimo.com/~scs/C-faq/s3.html[/color]
[color=blue]
> Note: The ASCII text version posted here by Steve Summit is
> more complete/up to date than the above HTML version but can
> be obtained following the links from
> http://www.eskimo.com/~scs/C-faq/top.html[/color]

ITYM also see FAQ 3.4, which answers the OP's question pretty much
directly.

--
/-- Joona Palaste (palaste@cc.hel sinki.fi) ------------- Finland --------\
\-------------------------------------------------------- rules! --------/
"I wish someone we knew would die so we could leave them flowers."
- A 6-year-old girl, upon seeing flowers in a cemetery

[Clark S. Cox III]

Re: expression evaluation : help!

On 2005-02-22 13:55:49 -0500, manan.kathuria@ gmail.com said:
[color=blue]
> hi all ,
> the expression in question is
>
> ++i&&++j||++k
>
> most sources say that since the result of the || operation is decided
> by the LHS itself , the right side is not computed[/color]

This is true. If the left-hand side of || is true, then the right-hand
side will never be evaluated. So, in your above expression, if (++i)
evaluates to a non-zero value, and (++j) does as well, then k will
never be incremented.
[color=blue]
> my point of thinking is that since the unary operator has higher
> precedence than || , it will be evaluated before || in any
> case........... where am im going wrong[/color]

The point that you're missing is that precedence has nothing to do with
order of evaluation.

--
Clark S. Cox, III
clarkcox3@gmail .com

[Michael Mair]

Re: expression evaluation : help!

Joona I Palaste wrote:[color=blue]
> Michael Mair <Michael.Mair@i nvalid.invalid> scribbled the following:
>[color=green]
>>manan.kathuri a@gmail.com wrote:
>>[color=darkred]
>>>hi all ,
>>>the expression in question is
>>>
>>>++i&&++j||++ k
>>>
>>>most sources say that since the result of the || operation is decided
>>>by the LHS itself , the right side is not computed
>>>
>>>my point of thinking is that since the unary operator has higher
>>>precedence than || , it will be evaluated before || in any
>>>case........ ...where am im going wrong[/color][/color]
>
>[color=green]
>>See FAQ 3.5 and 3.8, best read the whole section 3:
>> http://www.eskimo.com/~scs/C-faq/s3.html[/color]
>
>[color=green]
>>Note: The ASCII text version posted here by Steve Summit is
>>more complete/up to date than the above HTML version but can
>>be obtained following the links from
>> http://www.eskimo.com/~scs/C-faq/top.html[/color]
>
>
> ITYM also see FAQ 3.4, which answers the OP's question pretty much
> directly.[/color]

No, I plainly oversaw it when I was quickly scanning for special
questions to point out -- some people are scared by
"read the whole section" ;-)


Cheers
Michael
--
E-Mail: Mine is an /at/ gmx /dot/ de address.

[Joona I Palaste]

Re: expression evaluation : help!

Michael Mair <Michael.Mair@i nvalid.invalid> scribbled the following:[color=blue]
> Joona I Palaste wrote:[color=green]
>> Michael Mair <Michael.Mair@i nvalid.invalid> scribbled the following:[color=darkred]
>>>manan.kathur ia@gmail.com wrote:
>>>>hi all ,
>>>>the expression in question is
>>>>
>>>>++i&&++j||+ +k
>>>>
>>>>most sources say that since the result of the || operation is decided
>>>>by the LHS itself , the right side is not computed
>>>>
>>>>my point of thinking is that since the unary operator has higher
>>>>precedenc e than || , it will be evaluated before || in any
>>>>case....... ....where am im going wrong[/color]
>>[color=darkred]
>>>See FAQ 3.5 and 3.8, best read the whole section 3:
>>> http://www.eskimo.com/~scs/C-faq/s3.html[/color]
>>[color=darkred]
>>>Note: The ASCII text version posted here by Steve Summit is
>>>more complete/up to date than the above HTML version but can
>>>be obtained following the links from
>>> http://www.eskimo.com/~scs/C-faq/top.html[/color]
>>
>> ITYM also see FAQ 3.4, which answers the OP's question pretty much
>> directly.[/color][/color]
[color=blue]
> No, I plainly oversaw it when I was quickly scanning for special
> questions to point out -- some people are scared by
> "read the whole section" ;-)[/color]

Does your reply "no" to my "ITYM" mean "no, that's just plain wrong" or
"no, I didn't think of that"?

--
/-- Joona Palaste (palaste@cc.hel sinki.fi) ------------- Finland --------\
\-------------------------------------------------------- rules! --------/
"I am looking for myself. Have you seen me somewhere?"
- Anon

[Michael Mair]

Re: expression evaluation : help!

Joona I Palaste wrote:[color=blue]
> Michael Mair <Michael.Mair@i nvalid.invalid> scribbled the following:
>[color=green]
>>Joona I Palaste wrote:
>>[color=darkred]
>>>Michael Mair <Michael.Mair@i nvalid.invalid> scribbled the following:
>>>
>>>>manan.kathu ria@gmail.com wrote:
>>>>
>>>>>hi all ,
>>>>>the expression in question is
>>>>>
>>>>>++i&&++j|| ++k
>>>>>
>>>>>most sources say that since the result of the || operation is decided
>>>>>by the LHS itself , the right side is not computed
>>>>>
>>>>>my point of thinking is that since the unary operator has higher
>>>>>preceden ce than || , it will be evaluated before || in any
>>>>>case...... .....where am im going wrong
>>>
>>>>See FAQ 3.5 and 3.8, best read the whole section 3:
>>>> http://www.eskimo.com/~scs/C-faq/s3.html
>>>
>>>>Note: The ASCII text version posted here by Steve Summit is
>>>>more complete/up to date than the above HTML version but can
>>>>be obtained following the links from
>>>> http://www.eskimo.com/~scs/C-faq/top.html
>>>
>>>ITYM also see FAQ 3.4, which answers the OP's question pretty much
>>>directly.[/color][/color]
>[color=green]
>>No, I plainly oversaw it when I was quickly scanning for special
>>questions to point out -- some people are scared by
>>"read the whole section" ;-)[/color]
>
> Does your reply "no" to my "ITYM" mean "no, that's just plain wrong" or
> "no, I didn't think of that"?[/color]

The latter :-)


Cheers
Michael
--
E-Mail: Mine is an /at/ gmx /dot/ de address.

[manan.kathuria@gmail.com]

Re: expression evaluation : help!

thanks a lot everyone ....cheers
manan