MaplePrimes - Maple Posts and Questions

why _self is needed when using overload for object constructor?

nm — Fri, 15 May 2026 02:25:58 Z

I do not know if this is a bug or a feature.

Compare these two

The fix is that when using overload, one must explictly add _self. So it becomes _self:-_name:=name instead of just _name:=name when not using overload. Now it works.

But why? Is this a bug or there is a reason why one must add _self:- when using overload?

>	interface(version);

restart;

>	module person_type() option object; local _name::string; export ModuleCopy::static := overload([ proc( _self::person_type, proto::person_type, name::string,$) option overload; _name := name; end proc ]); end module:

>	o := Object(person_type, "me");

Error, static procedure `person_type:-ModuleCopy` refers to non-static local or export `person_type:-_name::string` in surrounding scope

restart;

>	module person_type() option object; local _name::string; export ModuleCopy::static :=proc( _self::person_type, proto::person_type, name::string,$) _name := name; end proc; end module:

>	o := Object(person_type, "me");

Download test_overload_in_OOP.mw

pdsolve and finite difference method discrepancy

wingho — Thu, 14 May 2026 15:58:52 Z

I was using pdsolve to solve for a 1-D longitudinal wave equation. My particular problem added an external stimulus that is not mechanical in original, so the acoustic wave velocity has to be modeled as a variable c(H) and I also have to add a du/dx term in the model. You can see my question posted on April 17, 2026. I was told that pdsolve does not handle such a problem. The suggestion in the posting is to use a finite difference method.

I am verifying that approach by solving a simplier problem where c is constant but with an initial uniformly stretched material. The solution does not seem to be physical. The material should relax throughout the whole length of the material, but the solution shows relaxation at the end and stay uniformly stretched at the center. I ran the problem with pdsolve and get a different result that I think is more realistic.

Is there something I can tweak in the finite difference approach to overcome that issue?

pde_finite_difference_method_linear_ic.mw

pdsolve_exercise_damping_ini_linear_a.mw

Calling object method in debugger

nm — Wed, 13 May 2026 17:47:51 Z

Is there a workaround to being able to call object method inside the debugger? I use Objects everywhere and hard to debug things when not able to try calls inside the debugger.

Here is an example.

This worksheet below has the code to reproduce this. Ofcourse the code works when I run it in the debugger using "continue" button, or using the "next" or "step". But I need sometimes to check something before doing this.

>	interface(version);

restart;

>	kernelopts('assertlevel'=2):

>	module person_type() option object; local _name::string:=""; export ModuleCopy::static := proc( _self::person_type, proto::person_type, name::string) _name:=name; NULL; end proc; export get_name::static:=proc(_self) _self:-_name; end proc; end module;

>	foo:=proc(o::person_type)::string; local name; DEBUG(); name:=o:-get_name(); name; end proc;

>	o:=Object(person_type,"me");

>	o:-get_name();

>	#run this. Debugger will now open foo(o);

Download why_calling_object_fail_in_debugger.mw

plotting an 1-D array

wingho — Mon, 11 May 2026 20:14:59 Z

Please see the attached worksheet:

Question 1: How to plot a partial portion of an array s2 using "dataplot," say the first 50 elements.

Question 2: I have also tried to use "plot" to plot the first 50 elements s2 and keep on getting errors or strange looking plot with horizontal lines. I have tried plot(s2,1..50), plot(s2,x=1..50), plot(s2,m=1..50), plot(s2[m],m=1..50), plot(s2[1..50],1..50], plot(1..50,s2[1..50]).

plot_exercise_a.mw

How apply special transformation ?

salim-barzani — Mon, 11 May 2026 08:09:36 Z

How i can apply this transfromation which is special and i can't undrestand how from that solution he did thus changes and get the solution of ode , i reached untill eq(3.5) but after that i can't figure out what he did and how we get eq(3.7)-(3.9) (3.12),(3.13) and how we can tranform solution for the eq(3.5)

fp.mw

Cube (hexahedron) and octahedron

Alfred_F — Fri, 08 May 2026 12:25:33 Z

To get better acquainted with "plot3d," I browsed through the help documentation. I was surprised to discover not only "Polyhedraplot," but—via "Polyhedra Sets" and "DualSet"—the very tools needed to tackle a classic subject: The duality of Platonic solids.
This reminded me of the following puzzle:
Consider the unit cube (edge length = 1) and, situated within it, its dual polyhedron (the octahedron). As is well known, the dual polyhedron of the octahedron is, in turn, a cube. Now, let us continue this dual construction indefinitely, starting from the unit cube (cube containing octahedron containing cube containing octahedron...). This generates a sequence of nested polyhedra—alternating between cubes and octahedra.
1.) For each of the infinite subsequences—that of the cubes and that of the octahedra—calculate the sum of all volumes and surface areas.
2.) What is the maximum volume an octahedron (regardless of its orientation) can have while being completely contained within the unit cube?