我最近选择了cpp并且做了几个非常小的项目来熟悉这门语言，而且我遇到了一个两难的问题，无论我在哪里看都无法弄清楚网页。
#include <iostream>
using namespace std;
int main(){
double salesTax = 0.875, gross = 0, tax = (gross*salesTax), total = (salesTax + gross); //Variables
cout << "Welome to StoreMart!" << endl;
cout << "How much is your total? "; //asks user for an amount of money spent (not including tax).
cin >> gross; //saves total spent in the gross variable
cout << "\n\nThat brings your total with tax to $" << total << "." << endl; //prints the users total with tax.
cout << "Price: " << gross << "$ \n\nSales Tax: $" << tax << " @" <<
salesTax << "% \n\nTotal: $" << total << endl; //prints out something similar to the receipts you get at Wal-Mart.
return 0;
}
正如你所知，我正在构建一个小型的收银机类型程序，但问题是每当运行时我只得到一个看起来像这样的输出。
http://imgur.com/7ndthUX（无法上传图片直到10分，所以希望imgur很好:)）
任何帮助都会受到赞赏（如果我的数学不合适，请不要介意我对让我的程序正常工作更感兴趣，而不是让数学更完美。）
答案 0 :(得分：2)
您正在根据gross根据初始值0计算所有值。在输出之前，获取gross输入，然后计算税金和总金额。
其他一些修正：
我已添加以下修复程序。
#include <iostream>
using namespace std;
int main(){
double salesTax = 0.0875;
double gross = 0;
double tax = 0;
double total = 0; //Variables with initial values
cout << "Welome to StoreMart!" << endl;
cout << "How much is your total? "; //asks user for an amount of money spent (not including tax).
cin >> gross; //saves total spent in the gross variable
tax = (gross*salesTax); //calculate tax
total = (tax + gross); //calculate total
cout.precision(2);
cout << "\n\nThat brings your total with tax to $" << total << "." << endl; //prints the users total with tax.
cout << "Price: " << gross << "$ \n\nSales Tax: $" << tax << " @" <<
salesTax*100 << "% \n\nTotal: $" << fixed << total << endl; //prints out something similar to the receipts you get at Wal-Mart.
return 0;
}
答案 1 :(得分：0)
当你编程时，你必须始终以与计算机“思考”相同的方式思考。代码从文件顶部到文件底部。也就是说，您在main的顶部编码的关系不是符号 - 您没有告诉计算机更新tax和total的值以反映从用户检索的新值gross。尝试从用户检索毛值后放置税和总分配语句。
答案 2 :(得分：0)
在打印新值到tax之后，您必须重新计算gross。
int main(){
double salesTax = 0.875;
double gross = 0;
double tax = 0;
double total = 0;
cout << "Welome to StoreMart!" << endl;
cout << "How much is your total? ";
cin >> gross;
tax = (gross*salesTax)
total = (salesTax + gross);
cout << "\n\nThat brings your total with tax to $" << total << "." << endl;
cout << "Price: " << gross << "$ \n\nSales Tax: $" << tax << " @" <<
salesTax << "% \n\nTotal: $" << total << endl;
return 0;
}
事实上，tax = (gross*salesTax)并未制定在gross或salesTax每次更改后都会更新的公式。它只是用当前指定的值计算tax。
答案 3 :(得分：0)
我认为你遇到的根本问题是你认为通过在顶部声明变量，你可以定义整个程序中它们之间的关系。但它并没有这样做。您在第10行输入了用户的毛重，但在上面，您已经根据毛的初始值分配了总数。
您必须了解变量是在声明它们的位置计算的。如果你为每个变量使用一个单独的行，那就更清楚了。
const double salesTax = 0.875;
double gross = 0; // set to zero now but input later
double tax = 0; // no point setting the tax until we know the gross
and so on...
然后你输入总量
cin >> gross;
然后根据输入计算税额等：
tax = (gross*salesTax); // now we can actually compute the tax because we have the gross
.... and so on
答案 4 :(得分：0)
C和C ++逐行执行代码，税和总计初始化为粗nad salesTax值的旧值以纠正您的程序尝试下面的代码
#include <iostream>
using namespace std;
int main(){
double salesTax = 0.875, gross = 0, tax = 0, total = 0; //Variables
cout << "Welome to StoreMart!" << endl;
cout << "How much is your total? "; //asks user for an amount of money spent (not including tax).
cin >> gross; //saves total spent in the gross variable
tax = (gross*salesTax); //calculating new tax after accepting gross value from user
total = (salesTax + gross);
cout << "\n\nThat brings your total with tax to $" << total << "." << endl; //prints the users total with tax.
cout << "Price: " << gross << "$ \n\nSales Tax: $" << tax << " @" <<
salesTax << "% \n\nTotal: $" << total << endl; //prints out something similar to the receipts you get at Wal-Mart.
return 0;
}