1 /* Octagonal_Shape class implementation (non-inline functions).
2 Copyright (C) 2001-2010 Roberto Bagnara <bagnara@cs.unipr.it>
3 Copyright (C) 2010-2016 BUGSENG srl (http://bugseng.com)
4
5 This file is part of the Parma Polyhedra Library (PPL).
6
7 The PPL is free software; you can redistribute it and/or modify it
8 under the terms of the GNU General Public License as published by the
9 Free Software Foundation; either version 3 of the License, or (at your
10 option) any later version.
11
12 The PPL is distributed in the hope that it will be useful, but WITHOUT
13 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
15 for more details.
16
17 You should have received a copy of the GNU General Public License
18 along with this program; if not, write to the Free Software Foundation,
19 Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02111-1307, USA.
20
21 For the most up-to-date information see the Parma Polyhedra Library
22 site: http://bugseng.com/products/ppl/ . */
23
24 #include "ppl-config.h"
25 #include "Octagonal_Shape_defs.hh"
26
27 namespace PPL = Parma_Polyhedra_Library;
28
29 #ifdef PPL_DOXYGEN_INCLUDE_IMPLEMENTATION_DETAILS
30 /*! \relates Parma_Polyhedra_Library::Octagonal_Shape */
31 #endif // defined(PPL_DOXYGEN_INCLUDE_IMPLEMENTATION_DETAILS)
32 bool
33 PPL::Octagonal_Shape_Helper
extract_octagonal_difference(const Constraint & c,const dimension_type c_space_dim,dimension_type & c_num_vars,dimension_type & c_first_var,dimension_type & c_second_var,Coefficient & c_coeff,Coefficient & c_term)34 ::extract_octagonal_difference(const Constraint& c,
35 const dimension_type c_space_dim,
36 dimension_type& c_num_vars,
37 dimension_type& c_first_var,
38 dimension_type& c_second_var,
39 Coefficient& c_coeff,
40 Coefficient& c_term) {
41 // Check for preconditions.
42 PPL_ASSERT(c.space_dimension() == c_space_dim);
43 PPL_ASSERT(c_num_vars == 0 && c_first_var == 0 && c_second_var == 0);
44
45 c_first_var = c.expression().first_nonzero(1, c_space_dim + 1);
46
47 if (c_first_var == c_space_dim + 1) {
48 c_term = c.inhomogeneous_term();
49 return true;
50 }
51
52 ++c_num_vars;
53 --c_first_var;
54
55 c_second_var = c.expression().first_nonzero(c_first_var + 2, c_space_dim + 1);
56
57 if (c_second_var == c_space_dim + 1) {
58 c_term = c.inhomogeneous_term();
59 const Coefficient& c0 = c.coefficient(Variable(c_first_var));
60 c_term *= 2;
61 c_first_var *= 2;
62 if (sgn(c0) < 0) {
63 c_second_var = c_first_var;
64 ++c_first_var;
65 }
66 else {
67 c_second_var = c_first_var + 1;
68 }
69 c_coeff = c0;
70 return true;
71 }
72
73 ++c_num_vars;
74 --c_second_var;
75
76 if (!c.expression().all_zeroes(c_second_var + 2, c_space_dim + 1)) {
77 return false;
78 }
79
80 using std::swap;
81
82 // FIXME: The calling code expects c_first_var > c_second_var, when
83 // c_num_vars==2, but it shouldn't.
84 swap(c_first_var, c_second_var);
85
86 // Make sure that `c' is indeed an octagonal difference,
87 // i.e., it is of this form:
88 // (+/-) a*x (+/-) a*y <=/= b.
89 c_term = c.inhomogeneous_term();
90 const Coefficient& c0 = c.coefficient(Variable(c_first_var));
91 const Coefficient& c1 = c.coefficient(Variable(c_second_var));
92 if (c0 != c1 && c0 != -c1) {
93 // Constraint `c' is not an octagonal difference.
94 return false;
95 }
96 c_first_var *= 2;
97 c_second_var *= 2;
98 if (sgn(c0) < 0) {
99 ++c_first_var;
100 }
101 if (sgn(c1) > 0) {
102 ++c_second_var;
103 }
104 c_coeff = c0;
105
106 return true;
107 }
108