[LMH]BIGNUM format?

[Nyef]

On Mon, 16 Jun 2003, Steve Krueger wrote:

> >    Do LDB and DPB behave, to a user, as if BIGNUMs are stored as 
> >2s-complement, as per ClTl, or does the abstraction break down there?
> 
> I think that the LDB and DPB microcode converts the relevant part of the 
> number to 2s-complement for this operation.  I'm looking into the 
> microcode for BIGNUM-LDB now.

Do you have this microcode source in machine-readable form? If so, can you 
actually quote the relevant part for us instead of summarizing?

> Yes the microcode is really full of this kind of twisty, very 
> conditional code.

Oh, I can believe it.

>     -Steve

Ah, thank you.

So, to confirm my understanding of what you're trying to say, do the 
following two expression => result pairs hold true for the explorer?

FIXNUM case: (ldb (byte 3 1) #x-8005) => 5
BIGNUM case: (ldb (byte 3 1) #x-8000000005) => -2

Or am I completely misinterpreting what you were trying to say?

---------------------------
All programming can be viewed as an exercise.
---------------------------
Alastair Bridgewater
e-mail: nyef@softhome.net