[Maxima-discuss] Dependencies and constantness

[Eduardo O. <edu...@gm...>]

Hi list,

the dependencies and the constantness of a variable seem to be stored
in two places - in "dependencies" and in properties(var). We can check
that with:

                         [properties(a), diff(a)];
  declare(a,constant)$   [properties(a), diff(a)];
  remove (a,constant)$   [properties(a), diff(a)];
                         [dependencies,  diff(a)];
  depends(a,[x,y])$      [dependencies,  diff(a)];
  remove (a,dependency)$ [dependencies,  diff(a)];

I tried to write a function "setdepends" that would work like this,

  setdepends(a,[])    - would declare a as constant
  setdepends(a,[a])   - would set a in the default way, with diff(a)=del(a)
  setdepends(a,[x,y]) - would work like depends(a,[x,y])

I tried to write it as:

  setdepends_const(var)      := (declare(var,constant),
remove(var,dependency))$
  setdepends_none (var)      := (remove (var,constant),
remove(var,dependency))$
  setdepends_other(var,deps) := (remove (var,constant), depends(var,deps))$
  setdepends      (var,deps) :=
    if     equal(deps,[])    then setdepends_const(var)
    elseif equal(deps,[var]) then setdepends_none (var)
    else                          setdepends_other(var,deps)$

  setdepends(a,[])$    diff(a);   /* should yield 0 */
  setdepends(a,[a])$   diff(a);   /* should yield del(a) */
  setdepends(a,[x,y])$ diff(a);   /* should yield a_x del(x) + a_y del(y) */

...but my code has lots of errors, and I'm finding it hard to debug. =(
Any suggestions?

  Thanks in advance,
    Eduardo Ochs
    http://anggtwu.net/eev-maxima.html