ch7 updated

7_41 to 7_46

Author: tsyw

Diff for: ch7/7_41.cc

@@ -0,0 +1,12 @@
+#include "7_41.h"
+#include <iostream>
+
+int main()
+{
+	Sales_data item1;
+	Sales_data item2("9-999-99999-2");
+	Sales_data item3("9-999-99999-2", 3, 15);
+	Sales_data item4(std::cin);
+
+	return 0;
+}

Diff for: ch7/7_41.h

@@ -0,0 +1,74 @@
+#ifndef EX7_41_H
+#define EX7_41_H
+
+#include <string>
+#include <iostream>
+
+using std::string;
+
+class Sales_data;
+Sales_data add(const Sales_data &lhs, const Sales_data &rhs);
+std::istream &read(std::istream &is, Sales_data &item);
+std::ostream &print(std::ostream &os, const Sales_data &item);
+
+class Sales_data
+{
+	friend Sales_data add(const Sales_data &, const Sales_data &);
+	friend std::istream &read(std::istream &, Sales_data &);
+	friend std::ostream &print(std::ostream &, const Sales_data &);
+	
+public:
+	Sales_data() : Sales_data("", 0, 0) { std::cout << "default" << std::endl; }
+	Sales_data(const string &s) : Sales_data(s, 0, 0) { std::cout << "only a string" << std::endl; }
+	Sales_data(const string &s, unsigned n, double p) : 
+			   bookNo(s), units_sold(n), revenue(p * n) { std::cout << "3 objects supplied" << std::endl; }
+	Sales_data(std::istream &is) : Sales_data() { read(is, *this); std::cout << "istream" << std::endl; }
+
+	Sales_data &combine(const Sales_data &);
+	string isbn() const;
+	
+private:
+	inline double avg_price() const
+	{
+		return units_sold ? revenue / units_sold : 0;
+	}
+
+	string bookNo;
+	unsigned units_sold = 0;
+	double revenue = 0.0;
+};
+
+string Sales_data::isbn() const
+{
+	return bookNo;
+}
+
+Sales_data &Sales_data::combine(const Sales_data &trans)
+{
+	units_sold +=trans.units_sold;
+	revenue += trans.revenue;
+	return *this;
+}
+
+Sales_data add(const Sales_data &lhs, const Sales_data &rhs)
+{
+	Sales_data sum = lhs;
+	sum.combine(rhs);
+	return sum;
+}
+
+std::istream &read(std::istream &is, Sales_data &item)
+{
+	double price = 0;
+	is >> item.bookNo >> item.units_sold >> price;
+	item.revenue = price * item.units_sold;
+	return is;
+}
+
+std::ostream &print(std::ostream &os, const Sales_data &item)
+{
+	os << item.isbn() << " " << item.units_sold << " " << item.revenue;
+	return os;
+}
+ 
+ #endif

Diff for: ch7/7_42.h

@@ -0,0 +1,27 @@
+#ifndef EX7_42_H
+#define EX7_42_H
+
+class Book;
+std::istream &readBook(std::istream &, Book &);
+
+class Book
+{
+public:
+	Book() : Book("", "", "") { }
+	Book(std::istream &is) : Book()
+	{
+		readBook(is, *this);
+	}
+	Book(std::string n, std::string::a, std::string p, std::string s) : name(n), author(a), press(p), subject(s) { }
+
+private:
+	std::string name, author, press, subject;	
+};
+
+std::istream &readBook(std::istream &is, Book &item)
+{
+	is >> item.name >> item.author >> item.press >> item.subject;
+	return is;
+}
+
+#endif

Diff for: ch7/7_43.h

@@ -0,0 +1,22 @@
+#ifndef EX7_43_H
+#define EX7_43_H
+
+class Nodefault
+{
+public:
+	Nodefault(int i) : ival(i) { }
+
+private:
+	int ival;
+};
+
+class C
+{
+public:
+	C() : nd(0) { }
+
+private:
+	Nodefault nd;
+};
+
+#endif

Diff for: ch7/7_44.cc

@@ -0,0 +1,10 @@
+class Nodefault
+{
+public:
+	Nodefault(int i) : ival(i) { }
+
+private:
+	int ival;
+};
+
+std::vector<NoDefault> vec(10);// illegal, have no default construction function

Diff for: ch7/7_45.cc

@@ -0,0 +1,20 @@
+class Nodefault
+{
+public:
+	Nodefault(int i) : ival(i) { }
+
+private:
+	int ival;
+};
+
+class C
+{
+public:
+	C() : nd(0) { }
+
+private:
+	Nodefault nd;
+};
+
+
+std::vector<C> vec(10);// legal

Diff for: ch7/7_46.cc

@@ -0,0 +1,4 @@
+// (a) false
+// (b) false
+// (c) false
+// (d) false