1 files changed, 103 insertions, 0 deletions
diff --git a/7p49.cpp b/7p49.cpp
new file mode 100644
index 0000000..3cf1c09
--- /dev/null
+++ b/7p49.cpp
@@ -0,0 +1,103 @@
+#include <iostream>
+
+/*
+ *
+ * 7.49
+ *
+ *
+ */
+
+struct SalesData;
+SalesData add(const SalesData&, const SalesData&);
+std::ostream &print(std::ostream&, const SalesData&);
+std::istream &read(std::istream&, SalesData&);
+struct SalesData {
+	SalesData() = default;
+	SalesData(const std::string &s): BookNo(s) { } //constructor, bookNo only
+	SalesData(const std::string &s, unsigned n, double p): // constructor, both bookno, UnitsSold and Revenue
+		BookNo(s), UnitsSold(n), Revenue(p*n) { }
+	SalesData(std::istream &sdcin) { read(sdcin, *this); }; // Constructor, but read from istream
+	std::string isbn() const { return BookNo; } // member function
+
+	//-------
+	SalesData &combine(SalesData);
+	//SalesData &combine(SalesData&);
+	//SalesData &combine(const SalesData&) const; Does not compile
+	//-------
+
+	inline double avg_price() const; // member function, defined elsewhere
+	std::string BookNo; // data member
+	unsigned int UnitsSold = 0; // data member
+	double Revenue = 0.0; // data member
+};
+
+inline double SalesData::avg_price() const {
+
+	if (UnitsSold)
+		return Revenue / UnitsSold;
+	else
+		return 0;
+}
+
+SalesData& SalesData::combine(SalesData rhs) {
+
+	UnitsSold += rhs.UnitsSold;
+	Revenue += rhs.Revenue;
+	return *this;
+}
+
+/*
+SalesData& SalesData::combine(SalesData &rhs) {
+
+	UnitsSold += rhs.UnitsSold;
+	Revenue += rhs.Revenue;
+	return *this;
+}
+*/
+/*
+SalesData& SalesData::combine(const SalesData &rhs) const {
+
+	UnitsSold += rhs.UnitsSold;
+	Revenue += rhs.Revenue;
+	return *this;
+}
+*/
+
+std::istream &read(std::istream &is, SalesData &item) { // Not member function
+
+	double price = 0;
+	is >> item.BookNo >> item.UnitsSold >> price;
+	item.Revenue = price * item.UnitsSold;
+	return is;
+}
+
+std::ostream &print(std::ostream &os, const SalesData &item) { // Not member function
+
+	os << item.isbn() << " " << item.UnitsSold << " "
+	   << item.Revenue << " " << item.avg_price();
+	return os;
+}
+
+SalesData add(const SalesData sd1, const SalesData sd2) { // Not member function
+
+	SalesData sdsum = sd1;
+	sdsum.combine(sd2);
+	return sdsum;
+}
+
+int main () {
+
+	/*
+	  For each of the three following declarations of combine, explain what
+	  happens if we call i.combine(s), where i is a Sales_data and s is a string:
+	  
+	  (a) SalesData &combine(Sales_data); It does not combine as expected, i'm not sure.
+	  (b) Sales_data &combine(Sales_data&);	// does not compile
+	  (c) Sales_data &combine(const Sales_data&) const; // does not compile
+	 */
+	std::string s = "7.49";
+	SalesData i("",0,0);
+	i.combine(SalesData(s));
+	print(std::cout, i);
+	return 0;
+}