negative bits

[Claus Dreischer]

Hi Bill,

not even close ;-)
(just kidding)

I needed to generate a sinus table with that generic bit representation (two's-complement) for a VHDL project.
Two's-complement is the internal format in which signed integers are stored.
Rev and Mark saved me.

Regards,
   Claus.


----- original Nachricht --------

Betreff: Re: negative bits
Gesendet: Mi, 02. Apr 2008
Von: Bill Marriott<wjm at wjm.org>

> Hi Claus,
> 
> I assume the reason why you're anticipating this result is because you are 
> used to Excel's DEC2BIN function available with the Analysis Add-On
> feature.
> 
> http://office.microsoft.com/en-us/excel/HP052090531033.aspx?pid=CH0625282410
> 33
> 
> Excel's DEC2BIN can only handle values between -512 to +511. And the results
> 
> it produces will of course be numbers that don't convert back the way you 
> expect in Revolution, either. For example, 11110111 is 247 in Rev.
> 
> If you want to get results consistent with Excel, the answer is to create 
> your own custom functions, DEC2BIN and BIN2DEC, that follow Excel's rules.
> 
> - Bill
> 
> "Claus Dreischer" <claus at dreischer.de> wrote in 
> message news:200804021410.m32EAEpc014923 at post.webmailer.de...
> Hi,
> 
> maybe someone has done this already ...
> 
> I'd like to convert integers into binary ones and zeros like
> input: "9" -> output "1001" or depending on the size of the output: 
> "00001001"
> 
> This can be done with the baseConvert function:
>    baseConvert( 9, 10, 2 ) gets me my "1001"
> 
> BUT (and we finaly get to the point)
> converting a *negative* integer number won't get me the desired result:
>    baseconvert( -9, 10, 2 )  -> "-1001"
> 
> The anticipated result would be "11110111"
> 
> So, how do i get there?
> Am i missing something?
> 
> Regards,
>    Claus. 
> 
> 
> 
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--- original Nachricht Ende ----