share/contrib/diffequations/odeutils.lisp

   1 ;; Author Barton Willis
   2 ;; University of Nebraska at Kearney
   3 ;; Copyright (C) 2004, Barton Willis
   4
   5 ;; Brief Description: Maxima code for linear homogeneous second order
   6 ;; differential equations.
   7
   8 ;; Maxima odelin is free software; you can redistribute it and/or
   9 ;; modify it under the terms of the GNU General Public License,
  10 ;; http://www.gnu.org/copyleft/gpl.html.
  11
  12 ;; Maxima odelin has NO WARRANTY, not even the implied warranty of
  13 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
  14
  15 ($put '$odeutils 1 '$version)
  16
  17 ;; Map the function f onto a mbag and simplify the result.  When the
  18 ;; bag is an equality, list, or matrix, simplification isn't needed;
  19 ;; however, new types of bags (say sets) may need simplification after
  20 ;; the mapping.
  21
  22 ;; Maxima is hit-or-miss about mapping functions over mbags. I suggest
  23 ;; we develop that a function similar to this one and that we use it
  24 ;; everywhere a function is mapped over a mbag.
  25
  26 ;; If the arguments of bag are in CRE form, margs changes them to general
  27 ;; form---and mbag-map may return an expression in general form. Maybe this
  28 ;; behavior is impolite?
  29
  30 (defun mbag-map (f bag)
  31   (simplify `((,(mop bag)) ,@(mapcar f (margs bag)))))
  32
  33 (defun number-of-unks (p unks)
  34   (let (($listconstvars nil))
  35     ($cardinality ($intersection ($setify ($listofvars p)) unks))))