Re: [Maxima-discuss] LispTree: Draw Maxima objects as trees (using Lisp)

[Stavros M. <mac...@gm...>]

When I was learning Lisp -- a very long time ago -- I found diagrams like
this useful for two purposes:

*1. Understanding structures with shared substructures.*

Maxima does use substructure sharing, but it has very few destructive
operations.
So a beginner at Maxima (especially if they don't have a Lisp background)
might have trouble understanding this:

l1: [a,b,c]$
l2: [d,e,f]$
lll: append(l1,[l1],[l2],l2)
    =>  [a, b, c, [a, b, c], [d, e, f], d, e, f]


l1[2]:bbb$
l2[2]:eee$
l1 => [a, bbb, c]
l2 => [d, eee, f]
lll => [a, b, c, [a, bbb, c], [d, eee, f], d, eee, f]

But it isn't necessary to explain this with box
<https://www.gnu.org/software/emacs/manual/html_node/elisp/Box-Diagrams.html>
diagrams
<https://www.gnu.org/software/emacs/manual/html_node/elisp/Box-Diagrams.html>
or
tree diagrams. It's enough to note that *append* shares its final
argument's representation with the result of *append*. In any case, to
diagram this, you need graph-structured (not tree-structured) displays,
which you don't support.


2. *Working out clever in-place algorithms*

... such as *nreverse*, which uses *rplacd* (See Steele's paper
<https://bitsavers.trailing-edge.com/pdf/mit/ai/aim/AIM-587.pdf> for an
example which is even more complicated, because he is working with cdr-coded
data <https://en.wikipedia.org/wiki/CDR_coding>.). Using box diagrams for
this can be helpful. But Maxima has nothing like *rplacd*.



On Mon, Oct 28, 2024 at 8:42 PM Eduardo Ochs <edu...@gm...> wrote:

> Hi Barton,
>
> you are right - the conversion from "Maxima objects" to "Maxima trees"
> is done in Maxima, by the functions in lisptree.mac whose names
> start with "lisptree0". Try:
>
>   load("/tmp/lisptree/lisptree.mac");
>   block([inflag:true],  lisptree(a/b));
>   block([inflag:false], lisptree(a/b));
>   block([inflag:true],  lisptree0(a/b));  /* [*,a,[^,b,-1]] */
>   block([inflag:false], lisptree0(a/b));  /* [/,a,b] */
>
> The function `lisptree0_apatom' calls `args', and if I remember
> correctly it is `args' that chooses between the representations a/b
> and a*b^-1 depending on the value of `inflag'... anyway, I just saw
> that it would be useful to have functions that generate trees like
> this one
>
>   MTIMES__.
>   |       |
>   $A      MEXPT__.
>           |      |
>           $B     -1
>
> from Maxima objects like a/b, i.e.,
>
>   ((MTIMES SIMP) $A ((MEXPT SIMP) $B -1))
>
> Here is a prototype. Run this in a REPL:
>
>   load("/tmp/lisptree/lisptree.mac");
>   block([inflag:true],  lisptree(a/b));
>   block([inflag:false], lisptree(a/b));
>   block([inflag:true],  format0(a/b));
>   block([inflag:false], format0(a/b));
>   o : a/b;
>   to_lisp();
>     #$o$
>
>     (defun newsimplify (o)
>       (if (and (consp o) (consp (car o)))
>           `(,(caar o) ,@(map 'list #'newsimplify (cdr o)))
>           o))
>     (defun $new2dtree_ (o)
>       (lisptree::toplain-lines (lisptree::lispytree (newsimplify o))))
>     (defun $new2dtree (o)
>       (format nil "~%~a" ($new2dtree_ o)))
>
>     ($new2dtree_ #$o$)
>     ($new2dtree  #$o$)
>     (to-maxima)
>
>   new2dtree(o);
>
> Here the output of its last line is this 2D tree:
>
>   MTIMES__.
>   |       |
>   $A      MEXPT__.
>           |      |
>           $B     -1
>
> Cheers, thanks for testing, more in other messages, etc,
>   Eduardo
>
>
> On Mon, 28 Oct 2024 at 13:32, Eduardo Ochs <edu...@gm...> wrote:
>
>> Hi Barton!
>>
>> I forgot to test it with inflag! I will do that very soon...
>>
>> I don't know how to use WxMaxima for non-trivial things. Anyone has
>> any idea of how to make it print multiline strings using a monospaced
>> font?
>>
>>   Cheers!
>>     Eduardo
>>
>>
>> On Mon, 28 Oct 2024 at 12:13, Barton Willis <wi...@un...> wrote:
>>
>>> Thanks for your contribution.
>>>
>>> Question: Am I correct that lisptree displays the internal structure
>>> when 'inflag' is true and otherwise shows the displayed structure?  These
>>> examples work okay:
>>>
>>>
>>> (%i28) block([inflag : true], lisptree(a/b));
>>> (%o28)
>>> *__.
>>> |  |
>>> a  ^__.
>>>    |  |
>>>    b  -1
>>>
>>> (%i29) block([inflag : false], lisptree(a/b));
>>> (%o29)
>>> /__.
>>> |  |
>>> a  b
>>> (%i30)
>>>
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