+/*
+ simple-spacer-scheme.cc -- implement Simple_spacer
+
+ source file of the GNU LilyPond music typesetter
+
+ (c) 2005 Han-Wen Nienhuys <hanwen@xs4all.nl>
+
+*/
+
+
+#include <cstdio>
+#include <math.h>
+
+#include "libc-extension.hh" // isinf
+#include "paper-column.hh"
+#include "spring.hh"
+#include "warn.hh"
+#include "simple-spacer.hh"
+
+LY_DEFINE(ly_solve_spring_rod_problem, "ly:solve-spring-rod-problem",
+ 4, 1, 0, (SCM springs, SCM rods, SCM length, SCM ragged),
+ "Solve a spring and rod problem for @var{count} objects, that "
+ "are connected by @var{count-1} springs, and an arbitrary number of rods "
+ "Springs have the format (ideal, hooke) and rods (idx1, idx2, distance) "
+ "@var{length} is a number, @var{ragged} a boolean "
+ "Return: a list containing the force (positive for stretching, "
+ "negative for compressing and #f for non-satisfied constraints) "
+ "followed by the @var{spring-count}+1 positions of the objects. "
+ )
+{
+ int len = scm_ilength (springs);
+ if (len == 0)
+ return scm_list_2 (scm_from_double (0.0), scm_from_double (0.0));
+
+ SCM_ASSERT_TYPE (len >= 0, springs, SCM_ARG1, __FUNCTION__, "list of springs");
+ SCM_ASSERT_TYPE (scm_ilength (rods) >= 0, rods, SCM_ARG2, __FUNCTION__, "list of rods");
+ SCM_ASSERT_TYPE (scm_is_number (length) || length == SCM_BOOL_F,
+ length, SCM_ARG3, __FUNCTION__, "number or #f");
+
+
+ bool is_ragged = ragged == SCM_BOOL_T;
+ Simple_spacer spacer;
+ for (SCM s = springs; scm_is_pair (s); s = scm_cdr (s))
+ {
+ Real ideal = scm_to_double (scm_caar (s));
+ Real hooke = scm_to_double (scm_cadar (s));
+
+ spacer.add_spring (ideal, hooke);
+ }
+
+ for (SCM s = rods; scm_is_pair (s); s = scm_cdr (s))
+ {
+ SCM entry = scm_car (s);
+ int l = scm_to_int (scm_car (entry));
+ int r = scm_to_int (scm_cadr (entry));
+ entry = scm_cddr (entry);
+
+ Real distance = scm_to_double (scm_car (entry));
+ spacer.add_rod (l, r, distance);
+ }
+
+ spacer.line_len_ = scm_to_double (length);
+
+ if (is_ragged)
+ spacer.my_solve_natural_len ();
+ else
+ spacer.my_solve_linelen ();
+
+ Array<Real> posns;
+ posns.push (0.0);
+ for (int i = 0; i < spacer.springs_.size(); i++)
+ {
+ Real l = spacer.springs_[i].length ((is_ragged) ? 0.0 : spacer.force_);
+ posns.push (posns.top() + l);
+ }
+
+
+
+ SCM force_return = SCM_BOOL_F;
+ if (!isinf (spacer.force_)
+ && (spacer.is_active () || is_ragged))
+ {
+ force_return = scm_from_double (spacer.force_);
+ }
+
+ if (is_ragged
+ && posns.top () > spacer.line_len_)
+ {
+ force_return = SCM_BOOL_F;
+ }
+
+ SCM retval = SCM_EOL;
+ for (int i = posns.size(); i--;)
+ {
+ retval = scm_cons (scm_from_double (posns[i]), retval);
+ }
+
+ retval = scm_cons (force_return, retval);
+ return retval;
+}