标签：class 使用 sign usr miss 影响 show 1.0 perm
方案一：结构体变量作为参数，进行传值。
编译器需要拷贝，不影响origin value，使用成员操作符(.)直接访问
/********************************************************************** * 版权所有 (C)2017, Wang maochun。 * * 文件名称：travel.cpp * 文件标识：无 * 内容摘要：主要演示结构体作为参数以及返回值 * 其它说明："传值” * 当前版本：V1.0 * 作 者：Wang maochun * 完成日期：2017.7.23 * **********************************************************************/ #include <iostream> struct travel_time { int hours; int mins; }; const int Mins_per_hr = 60; travel_time sum(travel_time t1,travel_time t2); void show_time(travel_time t); int main() { using namespace std; travel_time day1 = {5,45}; //5 hours 45 minutes travel_time day2 = {4,55}; //4 housr 55 minutes travel_time trip = sum(day1,day2); cout << "Two-day total:"; show_time(trip); travel_time day3 = {4,32}; cout << "Three-day total:"; show_time(sum(trip,day3)); return 0; } travel_time sum(travel_time t1,travel_time t2) { travel_time total; total.mins = (t1.mins + t2.mins) % Mins_per_hr; total.hours = (t1.hours + t2.hours) + (t1.mins + t2.mins) / Mins_per_hr; return total; } void show_time(travel_time t) { using namespace std; cout << t.hours << "hours," << t.mins << "minutes\n"; }
运行结果：
方案二：结构体指针作为参数，传地址。
编译器不需要拷贝，和main函数采用相同地址。为了不影响origin value，使用const修饰
使用指针指向结构体操作符(->)间接访问
/********************************************************************** * 版权所有 (C)2017, Wang maochun。 * * 文件名称：travel.cpp * 文件标识：无 * 内容摘要：主要演示结构体作为参数以及返回值 * 其它说明："传地址” * 当前版本：V1.0 * 作 者：Wang maochun * 完成日期：2017.7.23 * **********************************************************************/ #include <iostream> struct travel_time { int hours; int mins; }; const int Mins_per_hr = 60; travel_time sum(travel_time* t1,travel_time* t2); void show_time(travel_time* t); int main() { using namespace std; travel_time day1 = {5,45}; //5 hours 45 minutes travel_time day2 = {4,55}; //4 housr 55 minutes travel_time trip = sum(&day1,&day2); cout << "Two-day total:"; show_time(&trip); travel_time day3 = {4,32}; cout << "Three-day total:"; travel_time trip1 =sum(&trip,&day3); show_time(&(trip1)); return 0; } travel_time sum(travel_time* t1,travel_time* t2) { travel_time total; total.mins = (t1->mins + t2->mins) % Mins_per_hr; total.hours = (t1->hours + t2->hours) + (t1->mins + t2->mins) / Mins_per_hr; return total; } void show_time(travel_time* t) { using namespace std; cout << t->hours << "hours," << t->mins << "minutes\n"; }
结果和方案一相同。
出现的错误：
show_time(&(sum(&day1,&day2)));这样写时，出现taking address of temporary fpermissive错误。
原因是：
Your middle result which is a temporary variable since it will disappear
If you assign the result of sum(&day1,&day2) to a variable then it will no longer be a temporary and you can then take the address of it.
因此，不能对未赋值的临时变量取地址
标签：class 使用 sign usr miss 影响 show 1.0 perm
原文地址：http://www.cnblogs.com/shuqingstudy/p/7226413.html
