lt.c
2.21 KB
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/* X lt Y */
int fd_lt_filter(fd_constraint this)
{
fd_int x, y;
x = VAR(this, 0);
y = VAR(this, 1);
#ifndef DISABLE_ENTAILED
if (_fd_var_max(x) < _fd_var_min(y))
fd__constraint_set_entailed(this);
#endif
if (_fd_var_del_le(_fd_var_min(x), y))
{
if (fd_domain_empty(y))
return FD_NOSOLUTION;
_fd_revise_connected(NULL, y);
}
if (_fd_var_del_ge(_fd_var_max(y), x))
{
if (fd_domain_empty(x))
return FD_NOSOLUTION;
_fd_revise_connected(NULL, x);
}
return FD_OK;
}
int fd_lt_propagate2(fd_constraint this, fd_int culprit)
{
fd_int revise;
int changed = 0;
#if !defined(DISABLE_ENTAILED) && CONSTRAINT_TEMPS > 2
if (_fd_var_max(VAR(this, 0)) < _fd_var_min(VAR(this, 1)))
{
fd__constraint_set_entailed(this);
return FD_OK;
}
#endif
if (culprit == VAR(this, 0))
{
revise = VAR(this, 1);
changed = _fd_var_del_le(_fd_var_min(culprit), revise);
}
else
{
revise = VAR(this, 0);
changed = _fd_var_del_ge(_fd_var_max(culprit), revise);
}
if (changed && fd_domain_empty(revise))
return FD_NOSOLUTION;
if (changed)
_fd_revise_connected(0, revise);
return FD_OK;
}
int fd_lt_propagate(fd_constraint this, fd_int revise)
{
int changed = 0;
if (revise == VAR(this, 0))
changed = _fd_var_del_ge(_fd_var_max(VAR(this, 1)), revise);
else
changed = _fd_var_del_le(_fd_var_min(VAR(this, 0)), revise);
if (changed && fd_domain_empty(revise))
return FD_NOSOLUTION;
#ifdef USE_ENTAILED
if (_fd_var_max(VAR(this, 0)) < _fd_var_min(VAR(this, 1)))
_fd_constraint_set_entailed(this);
#endif
// XXX: enqueue further updates here?
if (changed)
_fd_revise_connected(this, revise);
return FD_OK;
}
fd_constraint fd_lt(fd_int x, fd_int y)
{
fd_constraint c = _fd_constraint_new(2, 0);
if (c)
{
c->variables[0] = FD_INT2C_VAR(x); c->variables[1] = FD_INT2C_VAR(y);
#ifdef CONSTRAINT_CLASS
c->kind = FD_CONSTR_LT;
#else /* CONSTRAINT_CLASS */
c->propagator2 = fd_lt_propagate2;
c->propagator = fd_lt_propagate;
#endif /* CONSTRAINT_CLASS */
_fd_var_add_constraint(x, c);
_fd_var_add_constraint(y, c);
_fd_add_constraint(c);
}
return c;
}