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Re: Digest Number
Joined: 18 Dec 2004
Posts: 1
Re: Digest Number
<< is bitwise left shift operator.
The result of the expression a << b
is a value that the value a is shifted right by b positions (bits).
(b number of bits removed from the left and b number of 0 bits added from right)
the value b should be less than the number of total bits of a
>> is bitwise right shift operator.
The result of the expression a >> b
is a value that the value a is shifted left by b positions (bits).
(b number of bits removed from the right and b number of 0 bits added from left (if a is unsigned or if a is a signed value greater than 0)
the value b should be less than the number of total bits of a
suppose that the integer 5 is represented as follows
0000 0000 0000 0101
5 >> 1 will be the value
0000 0000 0000 0010 (2)
5 >> 2 will be the value
0000 0000 0000 0001 (1)
5 << 1 will be the value
0000 0000 0000 1010 (10)
5 << 2 will be the value
0000 0000 0001 0100 (20)
in your main function, you call the function printf to write the value of integer expressions to stdout in decimal system,
I mean the expresions x, x << 2 and x >> 2.
nerg
----- Original Message -----
From: suresh kanna
To: Programmers-Town@yahoogroups.com
Sent: Thursday, December 16, 2004 3:50 PM
Subject: (PT) Digest Number
hello sir/mam,
can anyone can explain me how this program is solved manually and in compiler....
main()
{
int x=5;
printf("%d %d %d ",x,x<<2,x>>2);
}
The answer for this is 5,1,20... but how the answer is approached...
can anyone helpme.....
reply in suresh_hearts@...
thz,
with warm wishes bye,
suresh
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Joined: 27 Dec 2004
Posts: 14
Re: Digest Number
--- Shyan Lam <sflam@...> wrote:
> Reply embedded...
>
> > From: suresh kanna
> [mailto:suresh_hearts@...]
> > Sent: Thursday, December 16, 2004 7:51 AM
> > To: Programmers-Town@yahoogroups.com
> > Subject: (PT) Digest Number
> >
> > hello sir/mam,
> > can anyone can explain me how this program is
> solved manually and
> > in compiler....
> > main()
> > {
> > int x=5;
> > printf("%d %d %d ",x,x<<2,x>>2);
> > }
> > The answer for this is 5,1,20... but how the
> answer is approached...
> > can anyone helpme.....
>
> Do you understand what does the `<<` and `>>`
> operators do? What does your
> text said?
>
> They are called bit-shift operators.
>
>
> Bit 7 6 5 4 3 2 1 0
> +===============================+
> 5 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 1 |
> +===============================+
> | | |
> +-------+ | |
> | +-------+ |
> | | +-------+
> After << 2: v v v
> Bit 7 6 5 4 3 2 1 0
> +===================================+
> 20 | 0 | 0 | 0 | 1 | 0 | 1 | (0) | (0) |
> +===================================+
> ^^^^^^^^^^^ Two `0`
> pushed
> from
> right
>
>
> Bit 7 6 5 4 3 2 1 0
> +===============================+
> 5 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 1 |
> +===============================+
> | | |
> | | +-----------+
> | +-----------+ |
> +-----------+ | |
> After >> 2: v | |
> Bit 7 6 5 4 3 2 1 0 v v
> +===================================+ - - - +
> 1 | (0) | (0) | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 1 |
> +===================================+ - - - +
> ^^^^^^^^^^^^ ^^^^^^^^^
> Two `0` pushed Two bits
> pushed
> From left out
>
>
>
> In case your book did not mention it, the shift
> operator should be used on
> unsigned value.
>
> I suggest you read what the standard said when using
> the bitwise shift
> operator on signed value:
> <http://dev.unicals.com/c99-draft.html#6.5.7>
>
>
> > reply in suresh_hearts@...
>
> All reply should be sent to the group, for others to
> comments and reviews
> for correctness. All members should benefit from
> the discussions, not just
> you.
>
> HTH
> Shyan
>
>
Hi Shyam,
Can you please explain this the same procedure when
int x = -5;
Regards,
Ashwin Mittal.
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Joined: 24 Dec 2004
Posts: 3
Re: Digest Number
--- ashwin mittal <ashwin_mittal26@...> wrote:
>
>
>
> --- Shyan Lam <sflam@...> wrote:
>
> > Reply embedded...
> >
> > > From: suresh kanna
> > [mailto:suresh_hearts@...]
> > > Sent: Thursday, December 16, 2004 7:51 AM
> > > To: Programmers-Town@yahoogroups.com
> > > Subject: (PT) Digest Number
> > >
> > > hello sir/mam,
> > > can anyone can explain me how this program is
> > solved manually and
> > > in compiler....
> > > main()
> > > {
> > > int x=5;
> > > printf("%d %d %d ",x,x<<2,x>>2);
> > > }
> > > The answer for this is 5,1,20... but how the
> > answer is approached...
> > > can anyone helpme.....
> >
> > Do you understand what does the `<<` and `>>`
> > operators do? What does your
> > text said?
> >
> > They are called bit-shift operators.
> >
> >
> > Bit 7 6 5 4 3 2 1 0
> > +===============================+
> > 5 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 1 |
> > +===============================+
> > | | |
> > +-------+ | |
> > | +-------+ |
> > | | +-------+
> > After << 2: v v v
> > Bit 7 6 5 4 3 2 1 0
> > +===================================+
> > 20 | 0 | 0 | 0 | 1 | 0 | 1 | (0) | (0) |
> > +===================================+
> > ^^^^^^^^^^^ Two `0`
> > pushed
> > from
> > right
> >
> >
> > Bit 7 6 5 4 3 2 1 0
> > +===============================+
> > 5 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 1 |
> > +===============================+
> > | | |
> > | | +-----------+
> > | +-----------+ |
> > +-----------+ | |
> > After >> 2: v | |
> > Bit 7 6 5 4 3 2 1 0 v v
> > +===================================+ - - -
> +
> > 1 | (0) | (0) | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 1
> |
> > +===================================+ - - -
> +
> > ^^^^^^^^^^^^
> ^^^^^^^^^
> > Two `0` pushed Two
> bits
> > pushed
> > From left out
> >
> >
> >
> > In case your book did not mention it, the shift
> > operator should be used on
> > unsigned value.
> >
> > I suggest you read what the standard said when
> using
> > the bitwise shift
> > operator on signed value:
> > <http://dev.unicals.com/c99-draft.html#6.5.7>
> >
> >
> > > reply in suresh_hearts@...
> >
> > All reply should be sent to the group, for others
> to
> > comments and reviews
> > for correctness. All members should benefit from
> > the discussions, not just
> > you.
> >
> > HTH
> > Shyan
> >
> >
> Hi Shyam,
>
> Can you please explain this the same procedure when
> int x = -5;
>
> Regards,
> Ashwin Mittal.
>
>
>
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>
hi frnds,
u will be getting the ans 5 , 20 and 1 . but the ans
given is in the format of 5,1 and 20.
plz clear my doubt .
i have one more doubt , from which side does the C
starts processing the data.i.e
suppose this is the statement given to u.
printf("%d %d %d ",x,x<<2,x>>2);
then it will first print the o/p of x>>2 then x<<2
and then x or x then x<<2 and then x>>2.
plz clear my this doubt also.
from
amit
>
>
>
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Joined: 03 Jan 2005
Posts: 10
Re: Digest Number
Hi Ashwin,
>>In case your book did not mention it, the shift
>>operator should be used on
>>unsigned value.
>>
>>I suggest you read what the standard said when using
>>the bitwise shift
>>operator on signed value:
>> <http://dev.unicals.com/c99-draft.html#6.5.7>
>>
>>
>>
>
> Hi Shyam,
>
> Can you please explain this the same procedure when
> int x = -5;
>
> Regards,
> Ashwin Mittal.
>
DID YOU BOTHER TO READ SHYAN`S COMPLETE MAIL. JUST SEE THE STATEMENTS
ABOVE FROM SHYAN.
Kapil
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Joined: 25 Jul 2003
Posts: 48
Re: Digest Number
Hi,
> -----Original Message-----
> From: ashwin mittal [mailto:ashwin_mittal26@...]
> Sent: Monday, December 20, 2004 9:53 PM
> To: Programmers-Town@yahoogroups.com
> Subject: RE: (PT) Digest Number
>
>
> Hi Shyam,
>
> Can you please explain this the same procedure when
> int x = -5;
Did you read the link that I give (close to the end) in the previous reply?
In case you missed it, I reprint them here:
[quote]
I suggest you read what the standard said when using the bitwise shift
operator on signed value:
<http://dev.unicals.com/c99-draft.html#6.5.7>
[/quote]
It is either "undefined" or "implementation defined". You have to consult
the behavior to your compiler.
Shyan
Joined: 25 Jul 2003
Posts: 48
Re: Digest Number
Obviously he/she didn`t :(
> -----Original Message-----
> From: Kapil [mailto:taxikaps@...]
> Sent: Monday, December 20, 2004 11:39 PM
> To: Programmers-Town@yahoogroups.com
> Subject: Re: (PT) Digest Number
>
>
> DID YOU BOTHER TO READ SHYAN`S COMPLETE MAIL. JUST SEE THE STATEMENTS
> ABOVE FROM SHYAN.
>
Joined: 27 Dec 2004
Posts: 14
Re: Digest Number
>
> hi frnds,
>
> u will be getting the ans 5 , 20 and 1 . but the ans
> given is in the format of 5,1 and 20.
>
> plz clear my doubt .
>
> i have one more doubt , from which side does the C
> starts processing the data.i.e
> suppose this is the statement given to u.
> printf("%d %d %d ",x,x<<2,x>>2);
> then it will first print the o/p of x>>2 then x<<2
> and then x or x then x<<2 and then x>>2.
>
> plz clear my this doubt also.
>
> from
> amit
> >
> >
> >
HI Amit,
printf takes(processes) the argument from right to
left which u urself have mentioned. and the answers
is 5, 20 & 1.. It dispays the data in the same form in
which it is demanded...
Regards,
Ashwin Mittal.
__________________________________
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Joined: 25 Jul 2003
Posts: 48
Re: Digest Number
Reply embedded...
> -----Original Message-----
> From: harry potter [mailto:mummy_returns_arnold@...]
> Sent: Monday, December 20, 2004 11:40 PM
> To: Programmers-Town@yahoogroups.com
> Subject: RE: (PT) Digest Number( can any body tell me abt the order)
>
> hi frnds,
>
> u will be getting the ans 5 , 20 and 1 . but the ans
> given is in the format of 5,1 and 20.
I suppose the OP type it wrong. Or his compiler is broken.
A note for anyone posting codes and run results: To ensure we are reading
what you actually typed, please copy and paste codes from the compiler
instead of typing. As for run results, please copy and paste from the
command prompt (for Windows) or use redirect to a text file (if you use
stdout), and then copy and paste from the text file.
As for source code, please use spaces for indentation instead of tab.
Single line comments usually doesn`t works well with email (they got wrap
around), so use /* ... */
> plz clear my doubt .
>
> i have one more doubt ,
`Doubt` means you have some idea but not sure. I would really like to hear
what you think, and explain your "doubt" so that we can clear it. Or you
simply have a "question"?
> from which side does the C
> starts processing the data.i.e
"Data" is a very ambiguous term. What is your context? Rephrase and
explain what your real concern is. If you don`t know the exact terminology,
explain it with example.
> suppose this is the statement given to u.
> printf("%d %d %d ",x,x<<2,x>>2);
> then it will first print the o/p of x>>2 then x<<2
> and then x or x then x<<2 and then x>>2.
You`re talking about order of evaluation of function arguments, or how
printf() works?
For evaluation of function arguments:
Function arguments are not evaluated in any particular order, period. It
has nothing to do with "stack" or "push order".
C99 drift: 6.5.2.2p10:
The order of evaluation of the function designator, the actual
arguments, and subexpressions within the actual arguments is
unspecified, but there is a sequence point before the actual call.
Anybody tells you that function arguments are evaluated right-to-left
because function arguments are pushed right-to-left doesn`t know C.
For function call, this is what happens:
1. The arguments are evaluated, no in any particular order
2. All side effects are completed.
3. Call the function.
Inside printf() or any functions, it sees only the evaluated arguments.
For printf(), it will parse the format specifier, either output the
characters verbatim or format the passed argument as specify in the format
specifier.
So for example:
printf("%d %d %d ",x, x<<2, x>>2);
^ ^ ^ - ---- ----
| | | | | |
+--|--|---+ | |
+--|--------+ |
+-------------+
printf() would output the following:
- Value of `x` in decimal,
- One space,
- Value of the result of `x<<2` in decimal,
- One space,
- Value of the result of `x>>2` in decimal,
- One space.
Note that on some system, you might not get any output if your did not end
the format string with `
`.
HTH
Shyan
Joined: 29 Dec 2004
Posts: 31
Re: Digest Number
From: ashwin mittal [mailto:ashwin_mittal26@...]
>From: amit
>> hi frnds,
>>
>> u will be getting the ans 5 , 20 and 1 . but the ans
>> given is in the format of 5,1 and 20.
>>
>> plz clear my doubt .
>>
>> i have one more doubt , from which side does the C
>> starts processing the data.i.e
>> suppose this is the statement given to u.
>> printf("%d %d %d ",x,x<<2,x>>2);
>> then it will first print the o/p of x>>2 then x<<2
>> and then x or x then x<<2 and then x>>2.
It works out all three values first, then passes these results to
printf() - there is no predefined `order` in which these are called.
if x == 5 then
x<<2 == 5*2*2 == 10*2 == 20
x>>2 == (5/2)/2 == 2/2 == 1
>printf takes(processes) the argument from right to
>left which u urself have mentioned.
Not necesarily.
>and the answers
>is 5, 20 & 1.. It dispays the data in the same form in
>which it is demanded...
--
PJH
Quantum materiae materietur marmota monax si marmota monax materiam
possit materiari?
Alderley plc, Arnolds Field Estate, The Downs, Wickwar, Gloucestershire, GL12
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Joined: 31 Dec 2004
Posts: 2
Re: Digest Number
Hi Ashwin & Paul,
I think the answer given by Paul is correct. But i have a different reasoning for that answer. Normally C process the data from right to left for eg:printf("%d %d %d ",x,x<<2,x>>2);This behaviour is happens in majority of the cases but also from left to right processing is possible. Basically this direction of processing is guided by the way in which stack is implemented.
Regards,
S. Kumaran.
Paul Herring <pherring@...> wrote:
From: ashwin mittal [mailto:ashwin_mittal26@...] >From: amit>> hi frnds,>> >> u will be getting the ans 5 , 20 and 1 . but the ans>> given is in the format of 5,1 and 20.>> >> plz clear my doubt . >> >> i have one more doubt , from which side does the C>> starts processing the data.i.e >> suppose this is the statement given to u.>> printf("%d %d %d ",x,x<<2,x>>2);>> then it will first print the o/p of x>>2 then x<<2 >> and then x or x then x<<2 and then x>>2.It works out all three values first, then passes these results toprintf() - there is no predefined `order` in which these are called.if x == 5 thenx<<2 == 5*2*2 == 10*2 == 20x>>2 ==
(5/2)/2 == 2/2 == 1>printf takes(processes) the argument from right to>left which u urself have mentioned. Not necesarily.>and the answers>is 5, 20 & 1.. It dispays the data in the same form in>which it is demanded...--PJHQuantum materiae materietur marmota monax si marmota monax materiampossit materiari?Alderley plc, Arnolds Field Estate, The Downs, Wickwar, Gloucestershire, GL12 8JD, UKTel: +44(0)1454 294556 Fax: +44 (0)1454 299272Website : www.alderley.com Sales : sales@... Service : service@...This email and its contents are confidential and are solely for the use of the intended recipient. If you are not the original recipient you have received it in error and any use, dissemination, forwarding, printing or copying of this email is strictly prohibited. Should you receive this email in error please immediately notify
it@...This email has been scanned for viruses, however you should always scan emails with your own systems prior to opening.To unsubscribe : programmers-town-unsubscribe@yahoogroups.com
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