中国银行积分365,育知同创,实习医生格蕾下载
quote.h
#ifndef __quote_h__ #define __quote_h__ #include <iostream> class quote{ public: quote() = default; quote(const std::string& book, double pri) :bookno(book), price(pri){} std::string isbn() const{return bookno;} virtual double net_price(std::size_t n)const{ return n * price; } virtual ~quote() = default; private: std::string bookno; protected: double price = 0.0; }; class bulk_quote : public quote{ public: bulk_quote() = default; bulk_quote(const std::string&, double, std::size_t, double); double net_price(std::size_t n)const override; private: std::size_t min_qty = 0;//适用于折扣的最低购买数量 double discount = 0.0;//折扣额 }; //不小心在这个头文件里,加了下面这个函数的定义,结果导致编译时,提示这个函数被重复定义:( double print_total(std::ostream& os, const quote& item, size_t n){ double ret = item.net_price(n); os << "isbn: " << item.isbn() << " # sold: " << n << " total due: " << ret << std::endl; return ret; #endif
quote.cpp
#include "quote.h" bulk_quote::bulk_quote(const std::string& book, double p, std::size_t qty, double disc): quote(book, p), min_qty(qty), discount(disc){} double bulk_quote::net_price(std::size_t cnt)const { if(cnt >= min_qty){ return cnt * (1 - discount) * price; } else{ return cnt * price; } }
mainquote.cpp
#include "quote.h" int main(){ quote q("01",100.5); double d = print_total(std::cout, q, 1); bulk_quote bq("01", 100.5, 5, 1); }
编译方法:
g++ -g quote.cpp mainquote.cpp -std=c++11
编译结果:
multiple definition of `print_total(std::ostream&, quote const&, unsigned long)`
quote.h
#ifndef __quote_h__ #define __quote_h__ #include <iostream> class quote{ public: quote() = default; quote(const std::string& book, double pri) :bookno(book), price(pri){} std::string isbn() const{return bookno;} virtual double net_price(std::size_t n)const{ return n * price; } virtual ~quote() = default; private: std::string bookno; protected: double price = 0.0; }; class bulk_quote : public quote{ public: bulk_quote() = default; bulk_quote(const std::string&, double, std::size_t, double); double net_price(std::size_t n)const override; private: std::size_t min_qty = 0;//适用于折扣的最低购买数量 double discount = 0.0;//折扣额 }; #endif
quote.cpp
#include "quote.h" bulk_quote::bulk_quote(const std::string& book, double p, std::size_t qty, double disc): quote(book, p), min_qty(qty), discount(disc){} double bulk_quote::net_price(std::size_t cnt)const { if(cnt >= min_qty){ return cnt * (1 - discount) * price; } else{ return cnt * price; } } double print_total(std::ostream& os, const quote& item, size_t n){ double ret = item.net_price(n); os << "isbn: " << item.isbn() << " # sold: " << n << " total due: " << ret << std::endl; return ret; }
mainquote.cpp
#include "quote.h" int main(){ quote q("01",100.5); double d = print_total(std::cout, q, 1); bulk_quote bq("01", 100.5, 5, 1); }
编译结果:
error: ‘print_total’ was not declared in this scope
mainquote.cpp
#include "quote.h" double print_total(std::ostream& os, const quote& item, size_t n); int main(){ quote q("01",100.5); double d = print_total(std::cout, q, 1); bulk_quote bq("01", 100.5, 5, 1); }
如对本文有疑问,请在下面进行留言讨论,广大热心网友会与你互动!! 点击进行留言回复
如何在没有core文件的情况下用dmesg+addr2line定位段错误
用QT制作3D点云显示器——QtDataVisualization
网友评论