lily/simple-spacer-scheme.cc

   1 /*
   2   simple-spacer-scheme.cc -- implement Simple_spacer
   3
   4   source file of the GNU LilyPond music typesetter
   5
   6   (c) 2005--2007 Han-Wen Nienhuys <hanwen@xs4all.nl>
   7 */
   8
   9 #include <cstdio>
  10
  11 #include "paper-column.hh"
  12 #include "spring.hh"
  13 #include "warn.hh"
  14 #include "simple-spacer.hh"
  15
  16 LY_DEFINE (ly_solve_spring_rod_problem, "ly:solve-spring-rod-problem",
  17            4, 1, 0, (SCM springs, SCM rods, SCM length, SCM ragged),
  18            "Solve a spring and rod problem for @var{count} objects, that "
  19            "are connected by @var{count-1} springs, and an arbitrary number of rods "
  20            "Springs have the format (ideal, inverse_hooke) and rods (idx1, idx2, distance) "
  21            "@var{length} is a number, @var{ragged} a boolean "
  22            "Return: a list containing the force (positive for stretching, "
  23            "negative for compressing and #f for non-satisfied constraints) "
  24            "followed by the @var{spring-count}+1 positions of the objects. ")
  25 {
  26   int len = scm_ilength (springs);
  27   if (len == 0)
  28     return scm_list_2 (scm_from_double (0.0), scm_from_double (0.0));
  29
  30   SCM_ASSERT_TYPE (len >= 0, springs, SCM_ARG1, __FUNCTION__, "list of springs");
  31   SCM_ASSERT_TYPE (scm_ilength (rods)  > 0, rods, SCM_ARG1, __FUNCTION__, "list of rods");
  32   LY_ASSERT_TYPE (scm_is_number, length, 3);
  33
  34   bool is_ragged = ragged == SCM_BOOL_T;
  35   Simple_spacer spacer;
  36   for (SCM s = springs; scm_is_pair (s); s = scm_cdr (s))
  37     {
  38       Real ideal = scm_to_double (scm_caar (s));
  39       Real inv_hooke = scm_to_double (scm_cadar (s));
  40
  41       spacer.add_spring (ideal, inv_hooke);
  42     }
  43
  44   for (SCM s = rods; scm_is_pair (s); s = scm_cdr (s))
  45     {
  46       SCM entry = scm_car (s);
  47       int l = scm_to_int (scm_car (entry));
  48       int r = scm_to_int (scm_cadr (entry));
  49       entry = scm_cddr (entry);
  50
  51       Real distance = scm_to_double (scm_car (entry));
  52       spacer.add_rod (l, r, distance);
  53     }
  54
  55   spacer.solve (scm_to_double (length), is_ragged);
  56
  57   vector<Real> posns = spacer.spring_positions ();
  58
  59   SCM force_return = spacer.fits () ? scm_from_double (spacer.force ()) : SCM_BOOL_F;
  60
  61   SCM retval = SCM_EOL;
  62   for (vsize i = posns.size (); i--;)
  63     retval = scm_cons (scm_from_double (posns[i]), retval);
  64
  65   retval = scm_cons (force_return, retval);
  66   return retval;
  67 }