Re: Hexadecimal and bitwise operations

Hakusa@[EMAIL PROTECTED]
 wrote:

> I was asked to produce an M-tree class using unsigned ints in hex to
> traverse through and find nodes. The thing I'm having trouble working
> out is, I was given (on paper) 25E1 & 0010 = 00E0, but when I tried it
> on my computer, I found C++ converting it all to binary and producing
> 0x4 & 0x3 = 100 & 011 = 0.
> 
> Obviously, that's not helpful. How can I take my hex numbers and do
> the & operation? Or maybe my question is wrong--how can I access the
> n'th digit?

You have to distinguish between the number itself and its representation
to
a certain base. Mathematically the representation is not an intrinsic
property of a number.

The inner representation of numbers in a computer is binary, nothing else.
So there are some elementary operators to work on the binary
representation
of numbers but no elementary operators to work with hex, dec or any other
representation.

Thus to work with an arbitrary representation you have to convert the
number
to a string and then do string operations on the characters representing
your digits. I suggest to use std::stringstream for this.

In the case of hex you could utilize the fact that a hex digit represents
certain binary digits. Find a calculation that maps your 0010 to 0x00F0
and
then you get:

0x25E1 & 0x00F0 => 0x00E0

BTW, you didn't say if your 0010 is a string or a binary or a hex
representation of your input. The mapping you need depends on that fact.


> NOTE: This thread was created after about an hour or more of research.
> Simply pointing me in the right direction would be appreciated.
> 

Depending on the context an hour of research to solve an exercise might
not
be considered as long.

HTH
Björn


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