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//Download by http://www.NewXing.com /* * This file contains code from "C++ Primer, Fourth Edition", by Stanley B. * Lippman, Jose Lajoie, and Barbara E. Moo, and is covered under the * copyright and warranty notices given in that book: * * "Copyright (c) 2005 by Objectwrite, Inc., Jose Lajoie, and Barbara E. Moo." * * * "The authors and publisher have taken care in the preparation of this book, * but make no expressed or implied warranty of any kind and assume no * responsibility for errors or omissions. No liability is assumed for * incidental or consequential damages in connection with or arising out of the * use of the information or programs contained herein." * * Permission is granted for this code to be used for educational purposes in * association with the book, given proper citation if and when posted or * reproduced.Any commercial use of this code requires the explicit written * permission of the publisher, Addison-Wesley Professional, a division of * Pearson Education, Inc. Send your request for permission, stating clearly * what code you would like to use, and in what specific way, to the following * address: * * Pearson Education, Inc. * Rights and Contracts Department * 75 Arlington Street, Suite 300 * Boston, MA 02216 * Fax: (617) 848-7047 */ #include "tmpl_preamble.h" #include "Sales_item.h" // implement strcmp-like generic compare function // returns 0 if the values are equal, 1 if v1 is larger, -1 if v1 is smaller template <typename T> int compare(const T &v1, const T &v2) { if (v1 < v2) return -1; if (v2 < v1) return 1; return 0; } // repeats body of compare but with comments int f(int v1, int v2) { if (v1 < v2) return -1; // < on two objects of type T if (v2 < v1) return 1; // < on two objects of type T return 0; // return int; not dependent on T } // special version of compare to handle C-style character strings template <> int compare<const char*>(const char* const &v1, const char* const &v2) { return strcmp(v1, v2); } // returns 0 if the values are equal, -1 if v1 is smaller, 1 if v2 is smaller int compare(const string &v1, const string &v2) { if (v1 < v2) return -1; if (v2 < v1) return 1; return 0; } int compare(const double &v1, const double &v2) { if (v1 < v2) return -1; if (v2 < v1) return 1; return 0; } int main() { // T is int; // compiler instantiates int compare(const int&, const int&) cout << compare(1, 0) << endl; // T is string; // compiler instantiates int compare(const string&, const string&) string s1 = "hi", s2 = "world"; cout << compare(s1, s2) << endl; { short s1, s2; int i1, i2; compare(i1, i2); // ok: instantiate compare(int, int) compare(s1, s2); // ok: instantiate compare(short, short) } char *cp1 = "world", *cp2 = "hi"; cout << compare(cp1, cp2) << endl; // compares pointer values! { const char *cp1 = "world", *cp2 = "hi"; int i1, i2; compare(cp1, cp2); // calls the specialization compare(i1, i2); // calls the generic version instantiated with int } { const char *cp1 = "world", *cp2 = "hi"; compare<string>(cp1, cp2); // converts arguments to string } return 0; }