void guardt::guard_expr(exprt &dest) const
{
if(is_true())
{
// do nothing
}
else
{
if(dest.is_false())
{
dest=as_expr();
dest.make_not();
}
else
{
implies_exprt tmp;
tmp.op0()=as_expr();
tmp.op1().swap(dest);
dest.swap(tmp);
}
}
}
void make_it_a_predicate(
const predicatest &predicates,
exprt &expr,
const namespacet &ns)
{
bool negation;
canonicalize(expr, negation, ns);
// see if we have it
unsigned nr;
if(predicates.find(expr, nr))
{
// yes, we do!
// see if it is a constant
if(predicates[nr].is_true())
expr.make_true();
else if(predicates[nr].is_false())
expr.make_false();
else
{
expr=exprt(ID_predicate_symbol, typet(ID_bool));
expr.set(ID_identifier, nr);
}
if(negation)
expr.make_not();
}
else
{
// nah, we don't
// make it nondeterministic choice
exprt tmp(ID_nondet_symbol, typet(ID_bool));
tmp.add(ID_expression).swap(expr);
expr.swap(tmp);
}
}