lily/simple-spacer-scheme.cc

   1 /*
   2   This file is part of LilyPond, the GNU music typesetter.
   3
   4   Copyright (C) 2005--2011 Han-Wen Nienhuys <hanwen@xs4all.nl>
   5
   6   LilyPond is free software: you can redistribute it and/or modify
   7   it under the terms of the GNU General Public License as published by
   8   the Free Software Foundation, either version 3 of the License, or
   9   (at your option) any later version.
  10
  11   LilyPond is distributed in the hope that it will be useful,
  12   but WITHOUT ANY WARRANTY; without even the implied warranty of
  13   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14   GNU General Public License for more details.
  15
  16   You should have received a copy of the GNU General Public License
  17   along with LilyPond.  If not, see <http://www.gnu.org/licenses/>.
  18 */
  19
  20 #include <cstdio>
  21
  22 #include "paper-column.hh"
  23 #include "spring.hh"
  24 #include "warn.hh"
  25 #include "simple-spacer.hh"
  26
  27 LY_DEFINE (ly_solve_spring_rod_problem, "ly:solve-spring-rod-problem",
  28            4, 1, 0, (SCM springs, SCM rods, SCM length, SCM ragged),
  29            "Solve a spring and rod problem for @var{count} objects, that"
  30            " are connected by @var{count}-1 @var{springs}, and an arbitrary"
  31            " number of @var{rods}.  @var{count} is implicitly given by"
  32            " @var{springs} and @var{rods}.  The @var{springs} argument has"
  33            " the format @code{(ideal, inverse_hook)} and @var{rods} is of"
  34            " the form @code{(idx1, idx2, distance)}.\n"
  35            "\n"
  36            "@var{length} is a number, @var{ragged} a boolean.\n"
  37            "\n"
  38            "The function returns a list containing the force (positive for"
  39            " stretching, negative for compressing and @code{#f} for"
  40            " non-satisfied constraints) followed by @var{spring-count}+1"
  41            " positions of the objects.")
  42 {
  43   int len = scm_ilength (springs);
  44   if (len == 0)
  45     return scm_list_2 (scm_from_double (0.0), scm_from_double (0.0));
  46
  47   SCM_ASSERT_TYPE (len >= 0, springs, SCM_ARG1, __FUNCTION__, "list of springs");
  48   SCM_ASSERT_TYPE (scm_ilength (rods)  > 0, rods, SCM_ARG1, __FUNCTION__, "list of rods");
  49   LY_ASSERT_TYPE (scm_is_number, length, 3);
  50
  51   bool is_ragged = ragged == SCM_BOOL_T;
  52   Simple_spacer spacer;
  53   for (SCM s = springs; scm_is_pair (s); s = scm_cdr (s))
  54     {
  55       Real ideal = scm_to_double (scm_caar (s));
  56       Real inv_hooke = scm_to_double (scm_cadar (s));
  57
  58       Spring sp (ideal, 0.0);
  59       sp.set_inverse_compress_strength (inv_hooke);
  60       sp.set_inverse_stretch_strength (inv_hooke);
  61
  62       spacer.add_spring (sp);
  63     }
  64
  65   for (SCM s = rods; scm_is_pair (s); s = scm_cdr (s))
  66     {
  67       SCM entry = scm_car (s);
  68       int l = scm_to_int (scm_car (entry));
  69       int r = scm_to_int (scm_cadr (entry));
  70       entry = scm_cddr (entry);
  71
  72       Real distance = scm_to_double (scm_car (entry));
  73       spacer.add_rod (l, r, distance);
  74     }
  75
  76   spacer.solve (scm_to_double (length), is_ragged);
  77
  78   vector<Real> posns = spacer.spring_positions ();
  79
  80   SCM force_return = spacer.fits () ? scm_from_double (spacer.force ()) : SCM_BOOL_F;
  81
  82   SCM retval = SCM_EOL;
  83   for (vsize i = posns.size (); i--;)
  84     retval = scm_cons (scm_from_double (posns[i]), retval);
  85
  86   retval = scm_cons (force_return, retval);
  87   return retval;
  88 }