You can define such objects, but CAS generally don't
"understand" them particularly well, including Mathematica.
There's a KDELTA for Kronecker Delta in the tensor package.
But integration and simplification need to smarten up
to work with such things.
So the real answer may be: what do you want to
do with this? You might use tellsimp, etc. How
do you want to tie this in with (say) the derivative
of the abs function, or sign().
Perhaps you could try theta(x):=(abs(x)+x)/(2*x).
Not that this would make a CAS very happy.
Its derivative comes out zero, even at zero.
RJF
Albert Reiner wrote:
>Hi,
>
>is there some built-in / customary symbol or function for the
>unit-step function (Mathematica's UnitStep[], i.e.,
>
> Theta(x) = 1 for x > 0
> 0 for x < 0
>
>)?
>
>Thanks in advance (as well as for previous answers on various issues),
>
>Albert.
>
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