@gkokovidis: Thanks for your feedback. I have never received an analogous pop-up message. The plot thickens :-).

@Preben Alsholm: Thanks for your feedback. Good to hear that the issue is not just down to me goofing around :-).

@Sannis: The equation diff(p1(t), t) = -2*q1(t)-2 is correct; note, however, that I am talking about dH/dq.

@ecterrab: Much better than my workaround, of course. I was not aware of the option 'realobjects'. I am afraid that this ignorance of mine is due, at least partly, to a still missing text-book like introduction to the Physics package, a desire of mine voiced before, as you know.

PS: Analogous comments concerning the package DifferentialGeometry and its subspackage LieAlgebras apply. Without text-book like introductions/references from which to gain overviews of these packages, I seem unable to really begin using them. Almost every single time I try to do something with these packages, I get lost in the forest of help pages.

@macdy07: That indeed seems self-contradictory. Why, one may ask, does Maple have an option for specifying the value - any value, that is - of Heaviside at zero:

NumericEventHandler(invalid_operation = 
   `Heaviside/EventHandler`(value_at_zero = some value)
);

while at the same time using Heaviside(x)^2 = Heaviside(x), which is consistent only with Heaviside(0) being either 0 or 1?

Of course, under a Riemann integral, the value of Heaviside(0) matters nothing if Heaviside(x) is multiplied onto some non-distributional function. But it is, nonetheless, self-contradictory.

PS: Perhaps you should contact Maplesoft with these issues. I am not sure if it is the correct way to do it, but under 'More' in the menu bar of this site there is the option 'Submit Software Change Request'.

@shzan: I guessed that you did :-).

@mmcdara: I do not feel comfortable about your assertion that HD = 1/2(H^2)' = 1/2(H)' . For one thing, in line with vv's objection above, how do you define (the action of) HD? For another thing, why/how (H^2)' = H' ?

Update: I suddenly realize, that H^2 = H, and thus (H^2)' = H' as well, would hold quite simply if H(0) is defined to be either 0 or 1.

@sideshow: I would use spacecurve plots to plot your lines as curves in 3D, something along the following lines:

plots:-display([seq(seq(seq(
   plots:-spacecurve([x,A/B*x - A^2/B + B,C],x = -10..10)
,A = 1/4..1,1/4),B = 1/4..1,1/4),C = 1/4..1,1/4)]);

But I am confused: Maple returns a seemingly empty plot. Perhaps even more mysteriously, the help page on spacecurve seems to feature as well only empty plots. What is the point in that?, I ask myself.

@macdy07: You certainly seem to have a point concerning simplify, for why should your third and fourth expressions otherwise differ? I am curious what people at MapleSoft have to say about this.

PS: I had a little trouble getting your NumericEventHandler-line to work, until I realized that your 'Heaviside/EventHandler' should really read `Heaviside/EventHandler`.

@Markiyan Hirnyk: I guess you are right. Then macdy07 would seem to be correct, because then simply [using, as above, the Schwartz-Sobolev theory of distributions]

<DH,f> = <D,Hf> = H(0)f(0) = f(0) = <D,f>

so that DH = D, i.e., Dirac(x)*Heaviside(x) = Dirac(x). Or is there actually a problem with this? Consulting the book 'Generalized Functions: Theory and Technique', by R. P. Kanwal, it seems that H should be infinitely differentiable for the above to be readily well-defined, all derivatives being normal functions, that is. This is clearly not the case, all derivatives of H being genuine generalized functions.

@Preben Alsholm: I did not at all notice the missing assignments. Good that you did :-).

Maple returns NULL, i.e., it finds no solution. Write

sol := solve({eq3,eq4},{p[1],p[2]});

say, to clearly see that.

@VR88: You are welcome.

@aamirkhan: I see your problem. I am using Maple 17, where the problem, as mentioned, does not appear. So, I guess, it must be a post Maple 17 problem. But happy to learn that Edgardo S. Cheb-Terrab has solved your problem.

@aamirkhan: Where does it still exist?

PS: I assume that the quantities Cm(1 .. 3, 1 .. 8), Cm(4 .. 6, 1 .. 8), and Cm(7 .. 8, 1 .. 8) elsewhere in your worksheet have been changed as well, although even without these changes, I find that the worksheet executes without raising any error.