救命！ [英] Help!
问题描述
嘿伙计们，我在这个编程方面相对较新，而且我在这里停留了
的任务。我正在尝试让下面的程序响应
整数-1来停止并计算总数。确实如此，但它让我在加仑和里程下输入-1
，我该如何避免这种情况？谢谢。
//以加仑计算汽油里程数
#include< iostream>
#include< ; conio.h>
使用std :: cout;
使用std :: cin ;;
使用std ::固定;
#include< iomanip>
使用std :: setprecision;
//函数main开始程序执行
int main（）
{
int gal; //使用的加仑数
英里; //行驶里程数
int tg; //所有使用的加仑总数
int tm; //所有行驶里程总数
双mpg; //每加仑英里
总计双倍; //所有驱动器的平均值
//初始化阶段
tg = 0;
tm = 0;
while（gal！= -1）{
cout<< \ n输入使用的加仑数（输入-1表示完成）：\ n" ;;
cin>> gal;
cout<< 输入行驶里程：\ n;
cin>>里程;
tg = tg + gal;
tm = tm + miles;
//计算里程每加仑
mpg = static_cast<双> （英里）/加仑;
cout<< 这次旅行的每加仑是：\ n << setprecision（6）<<
fixed<< mpg;
}
if（gal！= 0）
total = static_cast<双> （tm）/ tg;
cout<< \ n总体平均值是：\ n" ;;
cout<<总计;
;返回0;
}
Hey guys, i am relatively new at this programming thing and am stuck on an
assignment here. I''m trying to get the program below to respond to the
integer -1 to stop and calculate total. It does, but it makes me enter -1
under both gallons and miles, how can i avoid this? Thanks.
//Figures gas mileage in gallons
#include <iostream>
#include <conio.h>
using std::cout;
using std::cin;;
using std::fixed;
#include <iomanip>
using std::setprecision;
// function main begins program execution
int main()
{
int gal; //number of gallons used
int miles; //number of miles driven
int tg; //total of all gallons used
int tm; //total of all miles driven
double mpg; //miles per gallon
double total; //average of all drives
//initialization phase
tg = 0;
tm = 0;
while ( gal != -1 ) {
cout << "\nEnter the gallons used (Enter -1 to finish) :\n";
cin >> gal;
cout << "Enter the miles driven:\n";
cin >> miles;
tg = tg + gal;
tm = tm + miles;
//calculate miles per gallon
mpg = static_cast < double > ( miles ) / gal;
cout << "The per gallon for this trip were :\n" << setprecision ( 6 ) <<
fixed << mpg;
}
if ( gal != 0 )
total = static_cast < double > ( tm ) / tg;
cout << "\nThe overall average was:\n";
cout << total;
;return 0;
}
推荐答案
Eric Whittaker写道：
Eric Whittaker wrote:
嘿伙计们，我对这个编程事物比较陌生，而且我在这里坚持了
任务。我正在尝试让下面的程序响应
整数-1来停止并计算总数。确实如此，但它让我在加仑和英里之间输入-1
，我怎么能避免这种情况呢？谢谢。
//数字汽油里程加仑
#include< iostream>
#include< conio.h>
使用std :: cout;
使用std :: cin ;;
使用std :: fixed;
#include< iomanip>
使用std :: setprecision;
//函数main开始程序执行
int main（）
{gal /; //使用的加仑数
英里; //行驶里程数
int tg; //所有使用的加仑总数
int tm; //所有行驶里程总数
双mpg; //每加仑英里
双倍总数; //所有驱动器的平均值
//初始化阶段
tg = 0;
tm = 0;
总计= 0.0;
//而（gal！= -1）{
for（;;）{/ / loop forever
cout<< " \ n输入使用的加仑数（输入-1表示完成）：\ n" ;;
cin>>加仑;
if（gal< 0）//在负加仑上退出循环
休息;
//忽略0加仑以防止''mpg'中的被零除错'calc
如果（gal == 0）
继续;
cout<< 输入行驶里程：\ n;
cin>>英里;
tg = tg + gal;
tm = tm +英里;
//计算每加仑英里数
mpg = static_cast<双> （英里）/加仑;
cout<< 这次旅行的每加仑是：\ n << setprecision（6）<<
fixed<< mpg;
}
// if（gal！= 0）
if（tg> 0）total = static_cast <双> （tm）/ tg;
cout<< \ n总体平均值为：\ n;
cout<<总计;
//;返回0;
返回0;
}
Hey guys, i am relatively new at this programming thing and am stuck on an
assignment here. I''m trying to get the program below to respond to the
integer -1 to stop and calculate total. It does, but it makes me enter -1
under both gallons and miles, how can i avoid this? Thanks.
//Figures gas mileage in gallons
#include <iostream>
#include <conio.h>
using std::cout;
using std::cin;;
using std::fixed;
#include <iomanip>
using std::setprecision;
// function main begins program execution
int main()
{
int gal; //number of gallons used
int miles; //number of miles driven
int tg; //total of all gallons used
int tm; //total of all miles driven
double mpg; //miles per gallon
double total; //average of all drives
//initialization phase
tg = 0;
tm = 0;
total = 0.0;
// while ( gal != -1 ) {
for (;;) { // loop forever
cout << "\nEnter the gallons used (Enter -1 to finish) :\n";
cin >> gal;
if (gal < 0) // quit loop on negative gallons
break;
// ignore 0 gallons to prevent divide-by-zero error in ''mpg'' calc
if (gal == 0)
continue;
cout << "Enter the miles driven:\n";
cin >> miles;
tg = tg + gal;
tm = tm + miles;
//calculate miles per gallon
mpg = static_cast < double > ( miles ) / gal;
cout << "The per gallon for this trip were :\n" << setprecision ( 6 ) <<
fixed << mpg;
}
// if ( gal != 0 )
if (tg > 0) total = static_cast < double > ( tm ) / tg;
cout << "\nThe overall average was:\n";
cout << total;
// ;return 0;
return 0;
}
问候，
拉里
-
反垃圾邮件地址，更改每个''X' 'to''。''直接回复。
Regards,
Larry
--
Anti-spam address, change each ''X'' to ''.'' to reply directly.
嘿谢谢拉里，使用（for）非常有帮助。我只是想在这里学习
，因为我的任务要求我使用（while）结构来完成这个任务，这是可能的，当我尝试它一直给我一个
未声明的标识符 - gal错误。
感谢您的帮助。
Hey thanks larry, the use of (for) is very helpful there. I''m just trying to
learn here, cause my assignment wants me to use a (while) structure to
accomplish this task, is this possible, when i try it keeps giving me a
"undeclared identifier - gal" error.
Thanks for all your help.
供将来参考，比帮助更具信息性的主题。将是一个好主意。
" Eric Whittaker" < EW **** @ adelphia.net>在留言中写道
新闻：oe ******************** @ adelphia.com
For future reference, a more informative subject line than "Help" would be a
good idea.
"Eric Whittaker" <ew****@adelphia.net> wrote in message
news:oe********************@adelphia.com
嘿伙计们，我我在这个编程方面相对较新，我在这里的任务上被困了。我正在尝试让下面的程序响应整数-1来停止并计算总数。它确实如此，但它让我在加仑和英里之间输入-1，我怎么能避免这种情况？
谢谢。
//数字汽油里程加仑
#include< iostream>
#include< conio.h>
使用std :: cout;
使用std :: cin ;;
使用std ::固定;
#include< iomanip>
使用std :: setprecision;
//函数main开始执行程序 int main（）
{gal /; //使用的加仑数
英里; //行驶里程数
int tg; //所有使用的加仑总数
int tm; //所有行驶里程总数
双mpg; //每加仑英里
双倍总数; //所有驱动器的平均值
//初始化阶段
tg = 0;
tm = 0;
请注意，第一次遇到gal！= -1时，gal未初始化。你将
设置为等于某个不等于-1的初始值。
while（gal！= -1）{
cout<< " \ n输入使用的加仑数（输入-1表示完成）：\ n" ;;
cin>>加仑;
这里的问题是gal！= - 1测试*之前*用户输入
gal值，所以你必须继续循环结束前循环
结束。你实际上不必在加仑和里程下输入-1。
输入-1后加仑，你可以输入任何里程和环路
还会结束。您可以通过各种方式处理此问题。一种方法是使用
而（真实）
{
cout<< \ n输入使用的加仑数（输入-1表示完成）：\ n" ;;
cin>> gal;
如果（gal == -1）
休息;
//循环的剩余部分
< br $>
}
另一种方法是在循环之前进行初始加仑查询并将所有
后续加仑查询作为最后一部分循环。
cout<< \ n输入使用的加仑数（输入-1表示完成）：\ n" ;;
cin>> gal;
while（gal！= -1）
{
cout<< 输入行驶里程：\ n;
cin>>里程;
tg = tg + gal;
tm = tm + miles;
//计算里程每加仑
mpg = static_cast<双> （英里）/加仑;
cout<< 这次旅行的每加仑是：\ n << setprecision（6）<<
fixed<< mpg;
cout<< \ n输入使用的加仑数（输入-1表示完成）：\ n" ;;
cin>> gal;
}
最后，你总是可以一次运行while循环，然后询问
用户*如果他们想继续或退出循环结束*并使用
答案设置你的while（）条件所依赖的变量（例如，
你可以定义一个bool keepGoing，你初始化为true，当用户表示他们想要退出时设置为
false，并使用while（keepGoing））。
cout<< ; 输入行驶里程：\ n;
cin>>英里;
tg = tg + gal;
tm = tm +英里;
//计算每加仑英里数
mpg = static_cast<双> （英里）/加仑;
cout<< 这次旅行的每加仑是：\ n << setprecision（6）
<<固定<< mpg;
}
如果（gal！= 0）
total = static_cast<双> （tm）/ tg;
cout<< \ n总体平均值为：\ n;
cout<<总;
因为你除以tg，我认为你应该测试tg！= 0，而不是
gal！= 0。你也可能想要一个块中的所有三行，即
if（tg！= 0）
{
总计= static_cast<双> （tm）/ tg;
cout<< \ n总体平均值是：\ n" ;;
cout<<总计;
}
;返回0;
这是什么;在行的开头？
}
Hey guys, i am relatively new at this programming thing and am stuck
on an assignment here. I''m trying to get the program below to respond
to the integer -1 to stop and calculate total. It does, but it makes
me enter -1 under both gallons and miles, how can i avoid this?
Thanks.
//Figures gas mileage in gallons
#include <iostream>
#include <conio.h>
using std::cout;
using std::cin;;
using std::fixed;
#include <iomanip>
using std::setprecision;
// function main begins program execution
int main()
{
int gal; //number of gallons used
int miles; //number of miles driven
int tg; //total of all gallons used
int tm; //total of all miles driven
double mpg; //miles per gallon
double total; //average of all drives
//initialization phase
tg = 0;
tm = 0;
Note that the first time gal != -1 is encountered, gal is uninitialised. You
should set it equal to some initial value that is unequal to -1.
while ( gal != -1 ) {
cout << "\nEnter the gallons used (Enter -1 to finish) :\n";
cin >> gal;
The problem here is that the gal!=-1 test is made *before* the user enters
the gal value, so you have to proceed to the end of the loop before the loop
finishes. You don''t actually have to enter -1 under both gallons and miles.
After you enter -1 for gal, you can enter anything for miles and the loop
will still end. You could handle this in various ways. One way is to use
while(true)
{
cout << "\nEnter the gallons used (Enter -1 to finish) :\n";
cin >> gal;
if(gal == -1)
break;
// remainder of loop
}
Another way is to have the initial gallons query before the loop and all
subsequent gallons queries as the final part of the loop.
cout << "\nEnter the gallons used (Enter -1 to finish) :\n";
cin >> gal;
while(gal != -1)
{
cout << "Enter the miles driven:\n";
cin >> miles;
tg = tg + gal;
tm = tm + miles;
//calculate miles per gallon
mpg = static_cast < double > ( miles ) / gal;
cout << "The per gallon for this trip were :\n" << setprecision ( 6 ) <<
fixed << mpg;
cout << "\nEnter the gallons used (Enter -1 to finish) :\n";
cin >> gal;
}
Finally, you could always have one run of the while loop and then ask the
user at the *end* of the loop if they want to continue or quit and use the
answer to set the variable on which your while() condition depends (e.g.,
you could define a bool keepGoing which you initialise to true and set to
false when the user indicates they want to quit, and use while(keepGoing)).
cout << "Enter the miles driven:\n";
cin >> miles;
tg = tg + gal;
tm = tm + miles;
//calculate miles per gallon
mpg = static_cast < double > ( miles ) / gal;
cout << "The per gallon for this trip were :\n" << setprecision ( 6 )
<< fixed << mpg;
}
if ( gal != 0 )
total = static_cast < double > ( tm ) / tg;
cout << "\nThe overall average was:\n";
cout << total;
Since you are dividing by tg, I think you should be testing tg!=0, not
gal!=0. You also probably want all three lines in a block, i.e.,
if ( tg != 0 )
{
total = static_cast < double > ( tm ) / tg;
cout << "\nThe overall average was:\n";
cout << total;
}
;return 0;
What is the ; at the start of the line for?
}
-
John Carson
--
John Carson
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