[Maxima-discuss] Methods

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

Hi list,

I always had the impression that defstruct was just the core of
something, and users were expected to write the rest... here is my
most recent attempt to write that "rest".

The code is just this,

  "@@4"(structname,o,method,Args) :=
     apply(concat(structname,"__",method), append([o],Args));

  "@@" (o,method) :=
     buildq([o,method], lambda([[Args]], "@@4"(op(o),o,method,Args)));

  infix("@@",200,201);

and here is a test:

  seqby(a,b,stp) := makelist(i, i,a,b,stp);   /* convenience */
  defstruct(poly(poly,var));
  poly__hi   (p)     := hipow(p@poly, p@var); /* methods */
  poly__coef (p,k)   := ratcoef (p@poly, p@var, k);
  poly__coefs(p,ks)  := makelist(p@@coef(k), k, ks);
  poly__L    (p)     := p@@coefs(seqby(p@@hi(),0,-1));

  myp : new(poly(10*x^2 + 20*x + 30, x));
  myp@@hi();                                  /* 2 */
  myp@@coefs([3,2,1,0]);                      /* [0, 10, 20, 30] */
  myp@@L();                                   /* [10, 20, 30] */

This will become a blog post (-ish) at some point, but that may take
some days.

  Cheers, all comments and pointers welcome =),
    Eduardo Ochs
    http://anggtwu.net/eev-maxima.html