C++写入文件

#include “iostream” #include “fstream” #include “cstdlib” using namespace std;

void file_it(ostream &os, double fo, const double fe[], int n); const int LIMIT = 5;

int main() { ofstream fout; const char *fn = “ep-data.txt”; fout.open(fn);

if(!fout.is_open()) { cout << "Can't open " << fn << ".Bye.\n"; exit(EXIT_FAILURE); } double objective; cout << "Enter the focal length of your " << "telescope objective in mm: "; cin >> objective; double eps[LIMIT]; cout << "Enter the focal lengths, in mm, of " << LIMIT << " eyepieces:\n"; for(int i =0;i<LIMIT;i++) { cout << "Eyepiece #" << i+1 << ": "; cin >> eps[i]; } file_it(fout, objective, eps, LIMIT);//写入文件 file_it(cout, objective, eps, LIMIT);//写到屏幕 cin.get(); cin.get(); return 0;

}

void file_it(ostream &os, double fo, const double fe[], int n) { ios_base::fmtflags initial; initial = os.setf(ios_base::fixed); //将对象置于使用定点表示法的模式 os.precision(0); //指定显示多少位小数 os << "Focal length of objective: " << fo << “mm\n”; os.setf(ios::showpoint); //将对象置于显示小数点的模式，即使小数部分为零 os.precision(1); //指定显示1位小数 os.width(12); //设置下一次输出操作使用的字符宽度 os << “f.1. eyepieces”; os.width(15); os << “magnification” << endl;

for(int i =0;i<n;i++) { os.width(12); os << fe[i]; os.width(15); os << int (fo/fe[i] + 0.5) << endl; } os.setf(initial);//恢复初始格式状态

}