update exercises 7.1--7.10

c++ note/chp7/exercise7_3.cpp

@@ -0,0 +1,23 @@
+#include "exercise7_2.h"
+
+int main() {
+	Sales_data total;							// variable to hold the running sum
+	if (read(cin, total)) {						// read the first transaction
+		Sales_data trans;						// variable to hold data for the next transaction
+		while (read(cin, trans)) {				// read the remaining transactions
+			if (total.isbn() == trans.isbn())	// check the isbns
+				total = total.combine(trans);	// update the running total
+			else {
+				print(cout, total) << endl;		// print the results
+				total = trans;					// process the next book
+			}
+		}
+		print(cout, total) << endl;				// print the last transaction
+	}
+	else {										// there was no input
+		cerr << "No data?!" << endl;			// notify the user
+	}
+
+	system("pause");
+	return 0;
+}