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/*
This file is part of LilyPond, the GNU music typesetter.
Copyright (C) 2005--2015 Han-Wen Nienhuys <hanwen@xs4all.nl>
LilyPond is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
LilyPond is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with LilyPond. If not, see <http://www.gnu.org/licenses/>.
*/
#include <cstdio>
#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 @var{springs}, and an arbitrary"
" number of @var{rods}. @var{count} is implicitly given by"
" @var{springs} and @var{rods}. The @var{springs} argument has"
" the format @code{(ideal, inverse_hook)} and @var{rods} is of"
" the form @code{(idx1, idx2, distance)}.\n"
"\n"
"@var{length} is a number, @var{ragged} a boolean.\n"
"\n"
"The function returns a list containing the force (positive for"
" stretching, negative for compressing and @code{#f} for"
" non-satisfied constraints) followed by @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_ARG1, __FUNCTION__, "list of rods");
LY_ASSERT_TYPE (scm_is_number, length, 3);
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 inv_hooke = scm_to_double (scm_cadar (s));
Spring sp (ideal, 0.0);
sp.set_inverse_compress_strength (inv_hooke);
sp.set_inverse_stretch_strength (inv_hooke);
spacer.add_spring (sp);
}
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.solve (scm_to_double (length), is_ragged);
vector<Real> posns = spacer.spring_positions ();
SCM force_return = spacer.fits () ? scm_from_double (spacer.force ()) : SCM_BOOL_F;
SCM retval = SCM_EOL;
for (vsize i = posns.size (); i--;)
retval = scm_cons (scm_from_double (posns[i]), retval);
retval = scm_cons (force_return, retval);
return retval;
}
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