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18.2.1.cc
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18.2.1.cc
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#include "18.2.1.h"
#include <iostream>
namespace cplusplus_primer{
using std::cout;
using std::endl;
Sales_data::Sales_data(const string & isbn):
isbn(isbn), unit_sold(0){}
Sales_data::Sales_data(const string & isbn, unsigned unit_sold):
isbn(isbn), unit_sold(unit_sold){}
Sales_data & Sales_data::operator+=(const Sales_data & item){
if(isbn != item.isbn)
throw isbn_mismatch("wrong isbn", isbn, item.isbn);
unit_sold += item.unit_sold;
return *this;
}
/* + 运算符不应该改变 原来的 */
Sales_data Sales_data::operator+(const Sales_data & item) const{
Sales_data tmp(*this);
try{
tmp.operator+=(item);
}catch(isbn_mismatch & e){
cout << e.what() << ": lhs(" << e.lhs << "), "
<< "rhs(" << e.rhs << ")" << endl;
}
return tmp;
}
}