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Rouben Rostamian

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19 years, 110 days
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These are questions asked by Rouben Rostamian

A puzzle on type-specification in a proc...

Rouben Rostamian 8541 Maple
May 30 2020
3 8

I want to write a proc, say f, that takes an single argument Z, as in
f := proc(Z::?) ...
where the only acceptable Z values are pairs [x,y], where x and y are selected from the set {a,b,c,d}. The entries a,b,c,d of that set are prescribed symbolic constants. 

Thus, the following are legal calls to f:
f([a,a]), f([a,b]), f([d,c])
but these are illegal:
f([a]), f([a,b,c]), f([a,x])

I don't know what to put for the "::?" in the proc's definition in order to enforce those constraints.  Any ideas?

Extra: In fact, I would prefer to ban the f([a,a]) option as well (no repeated symbols) but that's of secondary importance since it is easy to inspect and handle that within the proc's body.

Problem with starting Maple 2020 from th...

Rouben Rostamian 8541 Maple 2020
May 17 2020
1 1

Before Maple 2020, it was possible to start up Maple from the Linux commandline with multiple files, as  in

maple   -x   worksheet-1.mw   worksheet-2.mw   ...   worksheet-n.mw

That started up Maple's Java interface and loaded the n worksheets in separate tabs.

That no longer seems to work in Maple 2020 — now the command exits silently when invoked with multuple files.  Why?

Aside: Loading a single file works as expected, but not multiple files.

 

How to kill a Maple session...

Rouben Rostamian 8541 Maple 2020
vector convert
May 09 2020
3 1
> 

restart;
> 

kernelopts(version);

`Maple 2020.0, X86 64 LINUX, Mar 4 2020, Build ID 1455132`

> 

convert([1,2,3], Vector[row]);

Vector[row](3, {(1) = 1, (2) = 2, (3) = 3})

> 

convert([1,2,3], Vector[col]);

Trouble with pdsolve...

Rouben Rostamian 8541 Maple 2020
pde pdsolve differential-equations
May 09 2020
0 0

This worksheet shows an unexpected behavior of pdsolve().  It solves the heat equation on the interval (−1,1) but fails on the interval (0,1).  I see no technical reason for this happening — it's probably due to a little bug lurking somewhere.

> 

restart;
> 

kernelopts(version);

`Maple 2020.0, X86 64 LINUX, Mar 4 2020, Build ID 1455132`

> 

Physics:-Version();

`The "Physics Updates" package is not installed`

Solve the heat equation on the interval -1 < x and x < 1 and

boundary conditions u(-1, t) = 0, u(1, t) = 0.

> 

pde := diff(u(x,t),t) = diff(u(x,t),x,x);

diff(u(x, t), t) = diff(diff(u(x, t), x), x)

> 

bc := u(-1,t)=0, u(1,t)=0;

u(-1, t) = 0, u(1, t) = 0

> 

ic := u(x,0) = cos(Pi/2*x);

u(x, 0) = cos((1/2)*Pi*x)

> 

pdsol := expand(pdsolve({pde,bc,ic}));

u(x, t) = cos((1/2)*Pi*x)*exp(-(1/4)*t*Pi^2)

That's good.  Apply pdetest to verify it:

> 

pdetest(pdsol, [pde,bc,ic]);

[0, 0, 0, 0]

Now, solve the same problem on the interval 0 < x and x < 1 and

boundary condition u__x(0, t) = 0 and u(1, t) = 0.  It should be

evident that the solution remains the same as the one calculated

above, due to symmetry, and here is the verification:

> 

bc_new := D[1](u)(0,t)=0, u(1,t)=0;

(D[1](u))(0, t) = 0, u(1, t) = 0

> 

pdetest(pdsol, [pde,bc_new,ic]);

[0, 0, 0, 0]

But for some reason Maple's pdsolve fails to solve the PDE.  Actually

its response is somewhat erratic -- sometimes it returns nothing at all,

and sometimes it exits with an error message.

> 

pdsolve({pde,bc_new,ic});

 

Download pdsolve-fails.mw

 

Export to LaTeX not working properly...

Rouben Rostamian 8541 Maple 2020
latex export
April 18 2020
2 7

Does anyone here have experience with exporting Maple worksheets to LaTeX?  According to help page

?Export as latex

"You can change the Mathematics Formatting Width to align multi-line displayed formulas by modifying the option in the Export tab of the Options dialog."

That setting, however, seems to have no effect.  The image below shows the result, after setting the line width to (the extremely narrow!) 2 inches.  Long lines still overflow the left and right margins of the paper, rendering the result useless.

I see that this was pointed out in 2016 but there appears to have been no improvements since.  Does anyone know a workaround?  I am running Maple 2020 on Linux, if that matters.

This zip file z.zip contains a Maple worksheet, the exported *.tex file, and the compiled PDF.  Here is what that PDF looks like.

 

 

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