Bitwise operators

[den2k]

Re: Bitwise operators

On 19 Giu, 08:35, rahul <rahulsin...@gm ail.comwrote:

On Jun 19, 2:32 am, Santhosh <santhoshvenkat 1...@gmail.comw rote:
>

Hi to all,
How the individual digits of a number can be obtained using the
bitwise operators alone.Is it possible to do it ?

I do not think it is possible using only bitwise operators because
they work on a base-2 numbering system whereas you want to know the
_decimal_ digits.

[Richard Heathfield]

Re: Bitwise operators

den2k said:

On 19 Giu, 08:35, rahul <rahulsin...@gm ail.comwrote:

>On Jun 19, 2:32 am, Santhosh <santhoshvenkat 1...@gmail.comw rote:
>>

Hi to all,
How the individual digits of a number can be obtained using the
bitwise operators alone.Is it possible to do it ?

>
I do not think it is possible using only bitwise operators because
they work on a base-2 numbering system whereas you want to know the
_decimal_ digits.

We have already discussed the fact that addition can be done using the ^,
&, and << operators (XOR for add-without-carry, AND and LSH for obtaining
and moving the carry, repeat until no carry). Given addition, subtraction
is easy - simply take two's complement and add.

Given subtraction, division becomes not only possible but even easy.
Consider 34 / 10 (which we need to do if we're going to get the result 3
and remainder 4). 34 is 100010 in binary, and ten is 1010. Observe long
division in binary, noting that subtraction is done with ^ & << and the
two's complement, comparison can be done by subtraction, isolating the
bits necessary for the trial divisions can be done using shift and AND,
and "bringing down a bit" can be done with shift and OR:

1010)100010
1010 <---- Subtrahend <= minuend? No.

_0000
1010)100010
1010 <---- Subtrahend <= minuend? Yes. Subtract.

_00001
1010)100010
1010
---
111 <----- bring down a bit

_00001
1010)100010
1010
---
1110
1010 <---- Subtrahend <= minuend? Yes. Subtract.

_000011 <---- Result: 3
1010)100010
1010
---
1110
1010
---
100 <---- Remainder: 4

Yes, Virginia, you *can* divide by ten, even if you're thinking in binary.

--
Richard Heathfield <http://www.cpax.org.uk >
Email: -http://www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999