Exercise 15.9: Adding examples

ch15/README.md

@@ -54,6 +54,7 @@ The dynamic type is the type of the object in memory that the variable or expres
 > When is it possible for an expression’s static type to differ from its dynamic type? Give three examples in which the static and dynamic type differ.
 
 The static type of a pointer or reference to a base class may differ from its dynamic type. Anything like this can be an example.
+[Exercise 15.9](ex15.9/main.cpp)
 
 ## Exercise 15.10:
 > Recalling the discussion from §8.1 (p. 311), explain how the program on page 317 that passed an `ifstream` to the `Sales_data` read function works.

ch15/ex15.9/bulk_quote.cpp

@@ -0,0 +1,7 @@
+#include "bulk_quote.h"
+
+double Bulk_quote::net_price(std::size_t n) const
+{
+    std::cout << "Bulk_Quote net_price method got called" << std::endl;
+    return n * price * ( n >= min_qty ? 1 - discount : 1);
+}

ch15/ex15.9/bulk_quote.h

@@ -0,0 +1,19 @@
+#ifndef BULK_QUOTE_H
+#define BULK_QUOTE_H
+#include "quote.h"
+
+class Bulk_quote : public Quote
+{
+public:
+    Bulk_quote() = default;
+    Bulk_quote(const std::string& b, double p, std::size_t q, double disc) :
+        Quote(b, p), min_qty(q), discount(disc)  {   }
+
+    double net_price(std::size_t n) const override;
+
+private:
+    std::size_t min_qty     = 0;
+    double      discount    = 0.0;
+};
+
+#endif // BULK_QUOTE_H

ch15/ex15.9/limit_quote.cpp

@@ -0,0 +1,9 @@
+#include "limit_quote.h"
+
+double Limit_quote::net_price(std::size_t n) const
+{
+  if (n > max_qty)
+    return max_qty * price * discount + (n - max_qty) * price;
+  else
+    return n * discount *price;
+}

ch15/ex15.9/limit_quote.h

@@ -0,0 +1,20 @@
+#ifndef LIMIT_QUOTE_H
+#define LIMIT_QUOTE_H
+
+#include "quote.h"
+
+class Limit_quote : public Quote
+{
+public:
+    Limit_quote();
+    Limit_quote(const std::string& b, double p, std::size_t max, double disc):
+        Quote(b, p), max_qty(max), discount(disc)    {   }
+
+    double net_price(std::size_t n) const override;
+
+private:
+    std::size_t max_qty     = 0;
+    double      discount    = 0.0;
+};
+
+#endif // LIMIT_QUOTE_H

ch15/ex15.9/main.cpp

@@ -0,0 +1,45 @@
+/***************************************************************************
+ *  @file       main.cpp
+ *  @author     Hoesel Markus
+ *  @date       11  Apr 2016
+ *  @remark     This code is for the exercises from C++ Primer 5th Edition
+ *  @note
+ ***************************************************************************/
+//
+// Exercise 15.9:
+// When is it possible for an expression’s static type to differ from its 
+// dynamic type? Give three examples in which the static and dynamic type differ.
+//
+
+#include <iostream>
+#include <string>
+
+#include "quote.h"
+#include "bulk_quote.h"
+#include "limit_quote.h"
+
+int main()
+{
+    Bulk_quote bulk_quote("bulk_quote_1", 10.10, 10, 0.5);
+
+    // The pointer is of static type Quote, but it's dynamic type is Bulk Quote
+    // Because of polymorphism the Bulk Quote implementation of the net_price()
+    // method gets called.
+    Quote *quote_pointer = &bulk_quote;
+    quote_pointer->net_price(5);
+
+    // The reference is of static type Quote, but it's dynamic type is Bulk Quote
+    // Like with the pointer, the Bulk Quote implementation of the net_price()
+    // method gets called.
+    Quote &quote_reference = bulk_quote;
+    quote_reference.net_price(5);
+
+    // The static type of this variable is Quote. Here the Bulk Quote object
+    // gets upcasted. The Quote part of bulk_quote gets copied into quote, but
+    // the rest is not handled. Because of the cast the Quote implementation of
+    // the net_price() method gets called.
+    Quote quote = bulk_quote;
+    quote.net_price(5);
+
+    return 0;
+}

ch15/ex15.9/quote.cpp

@@ -0,0 +1,2 @@
+#include "quote.h"
+

ch15/ex15.9/quote.h

@@ -0,0 +1,30 @@
+#ifndef QUOTE_H
+#define QUOTE_H
+
+#include <string>
+#include <iostream>
+
+class Quote
+{
+public:
+    Quote() = default;
+    Quote(const std::string &b, double p) :
+        bookNo(b), price(p) { }
+
+    std::string     isbn() const { return bookNo; }
+    virtual double  net_price(std::size_t n) const { 
+      std::cout << "Quote net_price method got called" << std::endl;
+      return n * price; 
+    }
+
+    virtual ~Quote() = default;
+
+private:
+    std::string bookNo;
+
+protected:
+    double  price = 0.0;
+
+};
+
+#endif // QUOTE_H