src/desoln.lisp

   1 ;;; -*-  Mode: Lisp; Package: Maxima; Syntax: Common-Lisp; Base: 10 -*- ;;;;
   2
   3 (in-package :maxima)
   4
   5 (defmfun $desolve (eqns vars)
   6   (let (teqns tvars ovar (lvar ($gensym)) (flag nil) ($dispflag nil))
   7     (declare (special $dispflag))
   8     (if ($mapatom vars)
   9         (merror (intl:gettext "desolve(<eqn>,<depvar>): dependant variable <depvar> cannot be a mapatom, found: ~M") vars))
  10     (unless ($listp vars)
  11       (setq eqns (list '(mlist) eqns))
  12       (setq vars (list '(mlist) vars))
  13       (setq flag t))
  14     (setq ovar (maref vars 1))
  15     (unless (= ($length ovar) 1)
  16       (merror (intl:gettext "desolve: more than one independent variable: ~M") ovar))
  17     (setq ovar (simplify ($inpart ovar 1)))
  18     (setq teqns
  19      (simplify (map1 (getopr (m-tlambda&env (($z) (ovar lvar))
  20                                             nil
  21                                             (simplify ($laplace $z ovar lvar))))
  22                      eqns)))
  23     (setq tvars
  24      (simplify (map1 (getopr (m-tlambda&env (($z) (ovar lvar))
  25                                             nil
  26                                             (simplify `((%laplace) ,$z ,ovar ,lvar))))
  27                      vars)))
  28     (setq teqns
  29           (let ((errcatch (cons bindlist loclist))
  30                 (ret (errset (simplify ($solve teqns tvars)))))
  31             (when (null ret)
  32               (errlfun1 errcatch))
  33             (cons '(mlist) ret)))
  34     (when (or (like teqns '((mlist)))
  35               (like teqns (list '(mlist) '((mlist)))))
  36       ;; NOT CLEAR WHAT IS THE PROBLEM. SHOULD BE MORE EXPLICIT.
  37       (merror (intl:gettext "desolve: can't handle this case.")))
  38     (setq teqns (simplify ($first teqns)))
  39     (unless (like flag t)
  40       (setq teqns (simplify ($first teqns))))
  41     (setq teqns
  42      (simplify (map1 (getopr (m-tlambda&env (($z) (lvar ovar))
  43                                             nil
  44                                             (simplify ($ilt $z lvar ovar))))
  45                      teqns)))
  46     (if (and flag (= ($length tvars) 1))
  47         (maref teqns 1)
  48         teqns)))