private IEnumerable <Object> GetSubexpressions(ConsCell args)
{
try
{
return(args.GetListItems());
}
catch (System.InvalidOperationException)
{
throw new SyntaxException("Syntax error: Invalid expression.");
}
}
public IEnumerable <Object> GetListItems()
{
ConsCell current = this;
while (true)
{
if (current == Nil)
{
yield break;
}
yield return(current.Car);
if (!(current.Cdr is ConsCell))
{
throw new System.InvalidOperationException("This is not a list.");
}
current = (ConsCell)current.Cdr;
}
}
