// Would be nice to make this a virtual member function, but it's
// awkward with the recursion for list printing.
std::ostream& print(std::ostream& os, const ElemPtr& e, bool first=true)
{
SymbolPtr sym = to_symbol(e);
NumberPtr num = to_number(e);
if (sym)
{
os << sym->value();
}
else if (num)
{
os << num->value();
}
else
{
PairPtr p = to_cons(e);
if (p)
{
if (first)
os << "(";
if (is_nil(p))
os << ")";
else
{
if (!(to_symbol(p->car())))
os << "(";
print(os, p->car(), false);
if (!(is_nil(to_cons(p->cdr()))))
os << " ";
print(os, p->cdr(), false);
}
}
}
return os;
}
bool is_nil(const PairPtr& p)
{
return ((!(p->car())) && (!(p->cdr())));
}
