How can i compare bit wise?

[purifier]

Hi everyone,
I thought of writing a program which finds the greater of two numbers..
of course with a small condition... without using "if" and conditional
operators... I got an idea on how to implement the program... I have an
alternative too... that is to use bitwise comparison in the folowing
manner:
Accept the input
Subtract one number from the other
Check for the MSB(Most Significant Bit) in the result...
See if the result is positive or negative...
If negative then the second number is bigger...

Though i could think of the algorithm, i am unable to write a code in a
simple manner which can check the Most significant bit of the result...
How can do it...?

By the way, this was the logic i used for a simple solution:

/*The usual C statements*/
max=a+b+abs(a-b);
/*End of Program after the usual formalities*/

I just wanted to know how to test a single bit... whether it is
positive or negative i.e. 0 or 1...

And finally, is there any way i could print an integer in its binary
form directly without writing a program for that?

[purifier]

Oops...got the answer on how to check for the last bit..

x=number>>(size of(int)*8-1);

and then checking if x is 0 or non zero...

However the second part remains a puzzle to me... Is there any way i
can print binary form of an integer directly?

[Mike Wahler]

"purifier" <cn******@gmail .com> wrote in message
news:11******** **************@ c13g2000cwb.goo glegroups.com.. .

Oops...got the answer on how to check for the last bit..

x=number>>(size of(int)*8-1);

and then checking if x is 0 or non zero...

However the second part remains a puzzle to me... Is there any way i
can print binary form of an integer directly?

There is no built-in facility or function, but
writing one is not difficult. As a matter of
fact, if you search the archives of clc you should
find examples in code that I and others have
posted here in the past.

-Mike

[purifier]

Mike Wahler wrote:

"purifier" <cn******@gmail .com> wrote in message
news:11******** **************@ c13g2000cwb.goo glegroups.com.. .

Oops...got the answer on how to check for the last bit..

x=number>>(size of(int)*8-1);

and then checking if x is 0 or non zero...

However the second part remains a puzzle to me... Is there any way i can print binary form of an integer directly?

There is no built-in facility or function, but
writing one is not difficult. As a matter of
fact, if you search the archives of clc you should
find examples in code that I and others have
posted here in the past.

-Mike

Thanks Mike...
Actually i did write a program myself... but i was wondering if C
already had a built in function... anyway thanks for the
clarification.. .

[Keith Thompson]

"purifier" <cn******@gmail .com> writes:

Hi everyone,
Please stop creating new threads. Unless you have a separate question
(which you don't in this case), post a followup to the previous
thread.
I thought of writing a program which finds the greater of two numbers..
of course with a small condition... without using "if" and conditional
operators...
What exactly do you mean by "conditiona l operators"?
I got an idea on how to implement the program... I have an
alternative too... that is to use bitwise comparison in the folowing
manner:
Accept the input
Subtract one number from the other
Check for the MSB(Most Significant Bit) in the result...
See if the result is positive or negative...
If negative then the second number is bigger...
Subtraction can overflow. For example, if int is a 16-bit
2's-complement type (range -32768 .. +32767), subtracting -30000 from
+30000 yields 60000, which doesn't fit in an int. Even if you assume
some specific behavior on overflow, you're not going to get consistent
results.

[...]
And finally, is there any way i could print an integer in its binary
form directly without writing a program for that?

No. The *printf() functions support decimal, octal, and hexadecimal,
but not binary. But it's easy enough to implement it yourself.

--
Keith Thompson (The_Other_Keit h) 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.

[Keith Thompson]

"purifier" <cn******@gmail .com> writes:

Oops...got the answer on how to check for the last bit..

x=number>>(size of(int)*8-1);

and then checking if x is 0 or non zero...

What is the significance of the number 8? (Hint: CHAR_BIT, the number
of bits in a byte, isn't necessarily 8.)

If number is negative, the result of a right-shift operator is
implementation-defined.

You're also assuming that int has no padding bits (i.e., that you can
determine the number of significant bits from sizeof(int)). That's
true on most systems, but it's not guaranteed.

--
Keith Thompson (The_Other_Keit h) 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.

[Old Wolf]

purifier wrote:

Oops...got the answer on how to check for the last bit..

x=number>>(size of(int)*8-1);

and then checking if x is 0 or non zero...
That only works if 'number' is an unsigned int .
Right-shifts of a signed value are implementation-defined
as to whether the new bits are 0 or 1.

You could improve it slightly:

.. x = 1UL & (number >> sizeof number * CHAR_BIT - 1);

then it will work for any integral type (except for long long).

BTW, checking for the MSB does not necessarily indicate
positive or negative (although MSB = sign-bit is a very
common implementation) . The easiest way to check if
x is negative is: (x < 0)

However the second part remains a puzzle to me... Is there any way i
can print binary form of an integer directly?

You point to it with an (unsigned char *), and then
printf with "%02x" for each byte (if you want hex output).

Actually I have a similar problem to yours in some real code.
The poxy compiler I have to use, issues a compile-time warning
if a conditional is always true or always false, and there
is no way to turn that specific warning off. So I have
a macro:

#define IS_LT(x,y) (!!( ((ulong)(x) - (y)) & 0x8000000UL ))

that is non-zero if x < y . This macro does rely on some things
specific to my implementation (eg. size of ulong, and defined
behaviour on int overflow, in case x and y are signed int/long).
I don't entirely trust this macro; I only use it for
STATIC_ASSERTs.

[Jerry]

/*I write a simple routine just now*/
void int2bin(int ori)
{
int mask=0x01;
int len=sizeof(int) *8-1;
printf("%d",len );
while(len>-1)
{
printf("%d",(or i&(mask<<len--))?1:0);
}
}
/*well,anyhow,It works^_~*/

[Jack Klein]

On 19 Jan 2005 08:25:53 -0800, "purifier" <cn******@gmail .com> wrote
in comp.lang.c:

Hi everyone,
I thought of writing a program which finds the greater of two numbers..
of course with a small condition... without using "if" and conditional
operators... I got an idea on how to implement the program... I have an
alternative too... that is to use bitwise comparison in the folowing
manner:

Bit-wise is either poorly defined or undefined for signed integer
types, and useless for floating point types.

#include <stdio.h>
#include <limits.h>

int compare(int i1, int i2)
{
return (i1 >= i2) * i1 + (i1 < i2) * i2;
}

int main(void)
{
printf("greater of %d and %d is %d\n",
6, 12, compare(6, 12));
printf("greater of %d and %d is %d\n",
INT_MAX, INT_MIN, compare(INT_MAX , INT_MIN));
return 0;
}
--
Jack Klein
Home: http://JK-Technology.Com
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[sushant]

u can also mask the bits appropriately using the logical operators
instead of shifting ......