bool reduce_eq(expr_mark& is_var, expr* l, expr* r, expr_ref& v, expr_ref& t) {
if (is_var.is_marked(r)) {
std::swap(l, r);
}
if (is_var.is_marked(l)) {
contains_app cont(m, to_app(l));
if (!cont(r)) {
v = to_app(l);
t = r;
return true;
}
}
return false;
}
bool arith_solver_plugin::solve(expr * lhs, expr * rhs, expr_mark const & forbidden, app_ref & var, expr_ref & subst) {
rational k;
if (!m_simplifier.is_numeral(rhs, k))
return false;
bool _is_int = m_simplifier.is_int(lhs);
ptr_buffer<expr> monomials;
ptr_buffer<expr> todo;
bool already_found = false;
rational c;
todo.push_back(lhs);
while (!todo.empty()) {
expr * curr = todo.back();
todo.pop_back();
rational coeff;
if (m_simplifier.is_add(curr)) {
SASSERT(to_app(curr)->get_num_args() == 2);
todo.push_back(to_app(curr)->get_arg(1));
todo.push_back(to_app(curr)->get_arg(0));
}
else {
if (!already_found) {
if (m_simplifier.is_mul(curr) &&
m_simplifier.is_numeral(to_app(curr)->get_arg(0), coeff) && !coeff.is_zero() && (!_is_int || coeff.is_minus_one()) &&
is_uninterp_const(to_app(curr)->get_arg(1)) &&
!forbidden.is_marked(to_app(curr)->get_arg(1))) {
c = coeff;
var = to_app(to_app(curr)->get_arg(1));
already_found = true;
}
else if (is_uninterp_const(curr) && !forbidden.is_marked(curr)) {
c = rational::one();
var = to_app(curr);
already_found = true;
}
else {
monomials.push_back(curr);
}
}
else {
monomials.push_back(curr);
}
}
}
if (!already_found)
return false;
SASSERT(!c.is_zero());
k /= c;
expr_ref_vector new_monomials(m_manager);
if (!k.is_zero())
new_monomials.push_back(m_simplifier.mk_numeral(k, _is_int));
c.neg();
expr_ref inv_c(m_manager);
if (!c.is_one()) {
rational inv(1);
inv /= c;
inv_c = m_simplifier.mk_numeral(inv, _is_int);
}
// divide monomials by c
unsigned sz = monomials.size();
for (unsigned i = 0; i < sz; i++) {
expr * m = monomials[i];
expr_ref new_m(m_manager);
if (!c.is_one())
m_simplifier.mk_mul(inv_c, m, new_m);
else
new_m = m;
new_monomials.push_back(new_m);
}
if (new_monomials.empty())
subst = m_simplifier.mk_numeral(rational(0), _is_int);
else
m_simplifier.mk_add(new_monomials.size(), new_monomials.c_ptr(), subst);
TRACE("arith_solver", tout << "solving:\n" << mk_pp(lhs, m_manager) << "\n" << mk_pp(rhs, m_manager)
<< "\nresult:\n" << mk_pp(var, m_manager) << "\n" << mk_pp(subst, m_manager) << "\n";);