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Alejandro Jakubi

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These are answers submitted by Alejandro Jakubi

sum of variables of type "name"...

Alejandro Jakubi 2453
September 05 2014
2 3

You may use:

> type(z, '`+`'(name));
                                      true

Note that unevaluation quotes need to be used here, because the kernel procedure `+` makes an unary sum. Compare:

> `+`(name);
                                      name
> lprint('`+`'(name));
`+`(name)

Thus, as stated in ?type,structured:

`+`(type)                   a sum of terms of the given type

seems incorrect to me.

piecewise...

Alejandro Jakubi 2453
September 05 2014
1 1

The assumption mechanism should work for conveying the information to the system that a symbol represents a real variable. However, here the ouput of the integral, computed via the method FTOC, is expressed in a piecewise form, which is actually designed to handle real conditions rather than complex ones, see this simpler example:

> f:=piecewise(a+I*b>0,1,0);
                               { 1        0 < a + b I
                          f := {
                               { 0         otherwise

> simplify(f) assuming a::real,b::real;
                            { 0        a + b I <= 0
                            {
                            { 1        0 < a + b I

So, a workaround is using integral transform routines which, for some reason, are not tried in the computation of the integral. Something like:

> f:=1/((x+z1)*(x+z2)):
> sqrt(Pi/2)*(inttrans[fouriercos](f,x,t)+
> I*inttrans[fouriersin](f,x,t));
     1/2   1/2 / 1/2
1/2 2    Pi    |2    (cos(z1 t) Ci(z1 t) + sin(z1 t) Ssi(z1 t)
               \
                                                   /              1/2     1/2
     - cos(z2 t) Ci(z2 t) - sin(z2 t) Ssi(z2 t))  /  ((z1 - z2) Pi   ) + 2    (
                                                 /
    cos(z1 t) Ssi(z1 t) - sin(z1 t) Ci(z1 t) - cos(z2 t) Ssi(z2 t)
                               /              1/2 \
     + sin(z2 t) Ci(z2 t)) I  /  ((z1 - z2) Pi   )|
                             /                    /

it depends...

Alejandro Jakubi 2453
September 05 2014
1 1

It depends on the complete calculation. Note that symbols like a and b are implicitly assumed as complex by default, allowing the case a+I*b real.

why the result isn't a/d

Alejandro Jakubi 2453
September 05 2014
2 3

This is a good question. The prefix form of the product that is returned does not seem satisfactory to me:

> c:=a<b: 
> c/d; 
                                 *(a < b, 1/d)

It arises in `simpl/reloprod` line 16:

> stopat(`simpl/reloprod`,16): 
> c:=a/d:
> c/d;
1/d
`simpl/reloprod`:
  16*    return ('`*`')(args[relop],pr)
DBG> ('`*`')(args[relop],pr) 
`*`(a < b,1/d)
...

It would make much more sense that map were used instead, similarly to what Preben has shown.

Yet, this is at the syntactic level. A mathematical level way that takes into account the sign condition on d is needed.

PS It looks like there is a bug in rendering this post.

a history of lists...

Alejandro Jakubi 2453
August 26 2014
2 0

In this thread, Jacques told a bit on the history of Maple lists and how they have got the current design.

member...

Alejandro Jakubi 2453
August 25 2014
2 0

I think that ?member is not clear about the types allowed for its first argument. Probably it cannot be a container structure as the list c. Then, its elements have to be used individually as in:

> seq([member(i,A,'pos'),pos],i in c);
                    [true, 2, 1], [true, 2, 2], [true, 1, 3]

by extension...

Alejandro Jakubi 2453
August 23 2014
1 0

It goes more in line with the implementation for the standard constants to use a similar extension of evalf, like:

> constants := constants, phi;
       constants := false, gamma, infinity, true, Catalan, FAIL, Pi, phi
> `evalf/constant/phi`:=()->evalf((sqrt(5)+1)/2):
> evalf(phi);
                                  1.618033988
> type(phi+Pi,constant);
                                      true

organic ecosystem approach...

Alejandro Jakubi 2453
August 22 2014
1 5

It seems like Maplesoft is happy with that organic ecosystem approach to development...

There are several reasons for duplication. One reason is change of developer. The developer of the first command/package leaves and the developer that takes charge of the subject some time later has different design ideas, or the original code was not properly documented and it becomes simpler to rewrite than update.  Another reason is changes in the underlying system (language facilities, etc), also prompting rewrite. But newer packages frequently do not provide all the functionality of the older ones. And there is always library code somewhere depending on that old command. Hence, packages keep accumulating like geological layers...

modify this behavior...

Alejandro Jakubi 2453
August 22 2014
1 2

I think that there is no way to modify such behavior, change the assigned key, program a different editor action, etc. The Standard GUI is, I would say, monolithic and inflexible. A big problem, in my opinion. This is one of the reasons why I prefer using Maple in an IDE-like editor centric way. As the editor that I am using has an interface programming language, I can customize its behavior the way I like.

A previous thread...

Alejandro Jakubi 2453
August 20 2014
0 0

See also this thread. Note, however, that currently several comments are missing there. Presumably due to bugs in this site.

Typesetting:-mambiguous...

Alejandro Jakubi 2453
August 19 2014
0 0

In the Standard GUI Typesetting:-mambiguous is an internal function of the typesetting system (TypeMK) used to represent in output a parsing error and the like (the red-dotted rectangle). I know how to debug such issues in Standard, but never tried with MapleSim.

IF .. THEN .. ELIF ... FI, using the ope...

Alejandro Jakubi 2453
August 19 2014
2 0

You can use nested `if` calls like:

> map(x->if x<5 then f(x) elif x=5 then x else x-1 fi,A);
                        [1, 4, 9, 16, 5, 5, 6, 7, 8, 9]
> map(x->`if`( x<5, f(x), `if`(x=5,x,x-1)),A);
                        [1, 4, 9, 16, 5, 5, 6, 7, 8, 9]

I think that the main advantages of the operator form are compacteness and usage within expressions, like "Simple Case 2" in ?if > Examples.

by inert form...

Alejandro Jakubi 2453
August 12 2014
1 2

In the (automatic) normalization of the cos function call, the even symmetry is used like:

> cos(-x);
                                     cos(x)

So, a way for bypassing this normalization is using the inert form %cos instead:

> %cos(-x);
                                    %cos(-x)

Hence:

> li := a*%cos(7*x+8*x*y+9*y)*%cos(-7*x-8*x*y-9*y);
           li := a %cos(8 x y + 7 x + 9 y) %cos(-8 x y - 7 x - 9 y)
> ab:=7*x+8*x*y+9*y:
> ac:=20*y:
> subs(ab = ac, li);
                    a %cos(20 y) %cos(-8 x y - 7 x - 9 y)

top for Windows?...

Alejandro Jakubi 2453
August 12 2014
0 0

I wonder also whether there is a good equivalent. This thread is somewhat related. I guess that better answers could be got in a specialized Windows forum. Perhaps Cygwin is a way.

a bug...

Alejandro Jakubi 2453
August 05 2014
2 3

A priori, it looks like a bug. There is a procedure (assigned to) `pdsolve/BC/2nd_order/Series/2/integrate` and a procedure `pdsolve/BC/2nd_order/Series/4/integrate`, but not a procedure assigned to the name `pdsolve/BC/2nd_order/Series/3/integrate`. So the function call to the latter made in the the line 2 here:

> showstat(`pdsolve/BC/2nd_order/Series/3`);
`pdsolve/BC/2nd_order/Series/3` := proc(PDE, BC, F, INFOSET, series_hint)
local intermediate_result;
   1   if `PDEAdvisor/2nd_order/Series/3`(PDE,BC,F,INFOSET,'intermediate_result',series_hint) then
   2     `pdsolve/BC/2nd_order/Series/3/integrate`(intermediate_result)
       end if
end proc

remains as is, and so it returns.

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