Class IOLexerStack

Class IOLexerStack  is a derived class of LexerStack. It provides a mechanism of reading from a stack of istream's. Streams can be pushed and popped from the stack. The next token is obtained from the stream from the top of the stack. The class allows allows easy implementation of constructs such as the #include file mechanism of the C preprocessor.

The interface of this class is listed below:

class IOLexerStack : public IOLexerBuffer {
public:
   IOLexerStack();
   IOLexerStack(istream&);
   virtual ~IOLexerStack();

   virtual void     push_stream (istream&);
   virtual istream& pop_stream  ();
};