V9/include/CC/common.h

class istream;
class ostream;

struct common {
	virtual int	cmp(common& oo) { return this==&oo; }
		/* cmp performs a three way comparison if an ordering exists:
			this==arg: return 0,
			this<arg:  return negative,
			this>arg:  return positive
		   otherwise
			this==arg: return 0,
			this!=arg: return non-zero
		*/
	virtual int operator==(common& oo) { return this==&oo; }
	virtual char*	swho() { return 0; }
	virtual int	iwho() { return 0; }
	virtual int	size() { return sizeof(common); }
	virtual ostream&	write(ostream& s) { return s;}
	virtual istream&	read(istream& s) { return s; }
		common() {}
};