[Maxima] Maxima interface to Lisp bit-functions
van.nek at arcor.de
Mon Mar 17 14:20:14 CDT 2008
Am 17 Mar 2008 um 13:55 hat Stavros Macrakis geschrieben:
> On Mon, Mar 17, 2008 at 1:18 PM, van Nek <van.nek at arcor.de> wrote:
> > lsh(int, count): left shift
> > lsh(int): count=1 by default
> > rsh(int, count): right shift
> > rsh(int): count=1 by default
> I would recommend that you choose either lsh or rsh as
> and simplify the other one to it, e.g. rsh(x,2) == lsh(x,-2).
Stavros, my intention is the here, to make clear the shift direction just by the functions
name. The original Lisp function ash (artihmetric shift) doesn't do so. But you are right,
lsh(x,-1) is understandable as a shift to the right.
> > integer_length(int): length of the bit representation
> I assume you treat negative numbers as their two-complement
> e.g. logior(-1,x)=>-1.
> What is integer_length(-1)? Is it the same as
integer_length(-1) returns 0, because for negative integers it returns the position of the
leftmost zero (the leftmost 1 in case of positive ints).
So integer_length(-2^100) returns 100.
> > if at least one arg is a string, a Maxima list or constant but
> not an integer => merror
> Why not extend to non-integers? logior(1/2,1/3) => 5/6;
It was not my intention to handle these numbers. I just looked into the Mathematica doc and
they also only care about integers.
Stavros, do you see an interesting application of such to rationals extended bitwise
> There are many other useful simplifications, e.g. logand(x,x) =>
> logand(evenpobj,1) => 0, logior(x-1,-x) => -1, etc.
Right, these are useful simplifications. Can you give me any hint, how to manage them.
Thanks for your comments
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