public static IEnumerable <ISExpression> Flatten(this ISExpression s)
{
var ss = new List <ISExpression>();
if (s.IsNil())
{
ss.Add(s);
return(ss);
}
var ok = s is Cons;
while (ok)
{
var c = s as Cons;
ss.Add(c.Car);
s = c.Cdr;
ok = s is Cons;
}
if (s != AtomHelper.Nil)
{
throw new InvalidOperationException("list is not flat");
}
return(ss);
}
public static bool IsList(this ISExpression sexpr)
{
var c = sexpr as Cons;
return(sexpr.IsNil() ||
(c != null && (c.Cdr.IsNil() || c.Cdr.IsList())));
}