Bug in z_transform.mac?



-----maxima-bounces at math.utexas.edu wrote: -----


>FYI,?I'm?currently?adding?support?for?a?Heaviside?step?function
>hstep(x)?such?that?hstep(0)=1/2.??Perhaps?we?should?support?all?three
>common?variants?of?unit_step:?left-continuous,?right-continuous,?and
>hstep.??It?should?not?be?too?hard?to?search?for?all?occurrences?of
>unit_step?in?the?code?and?incorporate?support?for?the?other?variants.
>
>What?do?you?think?

There are simplifications  involving sums and products of these functions 
that would be difficult to detect; for example

  x * (left_continuous_step(x) -  right_continuous_step(x)) = 0.

Some days I think we should concentrate on making Maxima conditionals (if then else) 
better instead of appending more step-like functions. It be great if Maxima do

 (if x < 0 then 0 else 1) - (if x <= 0 then 0 else 1) --> if x = 0 then 1 else 0
 
and

  x * (if x = 0 then 1 else 0) --> 0.

At least for linear inequalities, I think this is algorithmically possible.

--Barton