iostream clear()

Question

istream &func(istream &in)
{
    string data;

    while (in >> data, !in.eof()) {
        if (in.bad())
            throw runtime_error("IO stream corrupted");
        if (in.fail()) {
            cerr << "bad data, try again" << endl;
            in.clear();
            in.ignore(200);
            continue;
        }   

        cout << data << endl;;
    }   

    //in.clear(istream::eofbit | istream::failbit);
    in.clear();

    return in; 
}

为什么in.clear(istream::eofbit | istream::failbit);不能重置cin？

但in.clear可以做到.

PS:我在main()中使用此函数,并将cin其用作参数.

Answer 1

clear定义如下:

void clear(iostate state = goodbit);

所以,实际上,in.clear();这样做:in.clear(istream::goodbit);重置流.调用in.clear(istream::eofbit | istream::failbit);将设置eofbit和failbit,我怀疑这是你想要的.

std::cin.clear(std::istream::eofbit | std::istream::failbit);
std::ios_base::iostate state = std::cin.rdstate();
if( state == (std::istream::eofbit | std::istream::failbit))
{
    std::cout << "eofbit and failbit set" << std::endl;
}