这段代码出啥问题了？？这是怎么回事呀？？？输出不了，sales-data构造函数有问题

#include
#include
using namespace std;
class sales_data
{
public:
sales_data( ) = default;
sales_data( const string & book): bookno(book){};
sales_data(const string & book,const unsigned num,const double sellp,const double salep);
sales_data(istream & is);

public:
string bookno;
unsigned units_sold = 0;
double sellingprice = 0.0;
double saleprice = 0.0;
double discount = 0.0;
};
sales_data::sales_data(const string & book,const unsigned num,const double sellp,const double salep)
{
bookno = book;
units_sold = num;
sellingprice = sellp;
saleprice = salep;
if(sellingprice != 0)
discount = saleprice / sellingprice;
}
sales_data::sales_data(istream & is)
{
is >> *this;
}
int main( )
{
sales_data data1;
sales_data data2("978-7-121-15535-2");
sales_data data3("978-7-121-15535-2",100,128,109);
sales_data data4(cin);
cout << "book sale explanation" << endl;
cout << data1 << " \n " << data2 <<"\n" << data3 <<"\n" <<data4<< "\n" <<endl;
return 0;