All that is true, but not terribly useful, since Maxima does very few
simplifications on unit_step, not even unit_step(x)*unit_step(-x) => 0.
-s
On Fri, Oct 7, 2011 at 13:26, Richard Hennessy <rich.hennessy at verizon.net>wrote:
> It has occurred to me on various occasions, that you can do logic in Maxima
> by using step functions. The unit_step() function, which is used in pw for
> representing piecewise functions, is bi-valued. So are Boolean expressions.
> You can represent connectors like "and", "or" and "not" as expressions
> involving unit_step().
>
> Consider if x>a and x>b then u else v;
>
> It is equivalent to the following, if you agree with the idea that how an
> expression evaluates is all that matters.
>
> (u - v) * unit_step(x - max(a, b)) + v;
>
> then there is "or" as in the following
>
> if x>a or x>b then u else v;
>
> It is equivalent to the following.
>
> (u - v) * unit_step(x - min(a, b)) + v;
>
> Another possibility is
>
> if (x > a) and (x < b) then u else v
>
> (v - u) * unit_step(x - b) + (u - v) * unit_step(x - a) + v
>
> Rich
> ______________________________**_________________
> Maxima mailing list
> Maxima at math.utexas.edu
> http://www.math.utexas.edu/**mailman/listinfo/maxima<http://www.math.utexas.edu/mailman/listinfo/maxima>;
>