> resources claiming that unit_step(x) and delta(x) functions
> exits for Maxima
Maxima does not define unit_step (though the commercial Macsyma
apparently did).
Fortunately, it is easy to define unit_step yourself:
unit_step(x):= if x<0 then 0 else 1;
That makes unit_step into a computational function, which requires x to
be numerical (or at least of known sign). This means that you can't
write
plot2d(unit_step(x),[x,-2,2])
because unit_step(x) is undefined for general x, and will give an error.
Instead, you'll need to quote the expression like this:
plot2d( '( unit_step(x) ), [x,-2,2] )
Since unit_step is user-defined and computational, you also can't use it
in symbolic expressions:
unit_step(x)*x^2
You can use the quoted (noun) form in such expressions:
expr: 'unit_step(x)*x^2
but Maxima doesn't have any mathematical knowledge of such functions:
integrate(expr,x,-1,1) => noun form
Hope this helps.
-s