8.1.2 条件状态

书中页数：P282
代码名称：clearIO.cc

#include <iostream>
using std::cin; using std::cout; using std::endl;

#include <sstream>
using std::istringstream;

#include <string>
using std::string;

void read()
{
	// turns on both fail and bad bits
	cin.setstate(cin.badbit | cin.eofbit | cin.failbit);
}

void off()
{
	// turns off failbit and badbit but all other bits unchanged
	cin.clear(cin.rdstate() & ~cin.failbit & ~cin.badbit);
}


int main()
{
	cout << "before read" << endl;
	if (cin.good()) cout << "cin's good" << endl;
	if (cin.bad()) cout << "cin's bad" << endl;
	if (cin.fail()) cout << "cin's fail" << endl;
	if (cin.eof()) cout << "cin's eof" << endl;

	read();
	cout << "after read" << endl;
	if (cin.good()) cout << "cin's good" << endl;
	if (cin.bad()) cout << "cin's bad" << endl;
	if (cin.fail()) cout << "cin's fail" << endl;
	if (cin.eof()) cout << "cin's eof" << endl;

	off();
	cout << "after off" << endl;
	if (cin.good()) cout << "cin's good" << endl;
	if (cin.bad()) cout << "cin's bad" << endl;
	if (cin.fail()) cout << "cin's fail" << endl;
	if (cin.eof()) cout << "cin's eof" << endl;

	return 0;
}