#include <algorithm>
#include <iomanip>
#include <ios>
#include <iostream>
#include <string>
#include <vector>
using std::cin; using std::sort;
using std::cout; using std::streamsize;
using std::endl; using std::string;
using std::setprecision; using std::vector;
int main()
{
cout << "Please enter your midterm and final exam grades: ";
double midterm, final;
cin >> midterm >> final;
cout << "Enter all your homework grades, "
"followed by end-of-file: ";
vector<double> homework;
double x;
while (cin >> x)
homework.push_back(x);
int size = homework.size();
if (size == 0) {
cout << endl << "You must enter your grades. "
"Please try again." << endl;
return 1;
}
sort(homework.begin(), homework.end());
int mid = size/2;
double median;
median = size % 2 == 0 ? (homework[mid] + homework[mid-1]) / 2
: homework[mid];
streamsize prec = cout.precision();
cout << "Your final grade is " << setprecision(3)
<< 0.2 * midterm + 0.4 * final + 0.4 * median
<< setprecision(prec) << endl;
return 0;
}
在这个例子中,“streamsize”的意义何在?为什么 cout.precision() 会这样设置?以下行有“setprecision(3)”,然后在末尾再次有 setprecision(prec)。这是为什么?
streamsize prec = cout.precision();
cout << "Your final grade is " << setprecision(3)
<< 0.2 * midterm + 0.4 * final + 0.4 * median
<< setprecision(prec) << endl;