创建循环以用C ++编写多个文件？

Question

Let's say I have a program that does the follow:

for (i=1; i<10; i++)
{
   computeB(i);
}

where the computeB just outputs a list of values

computeB(int i)
{
  char[6] out_fname="output";
  //lines that compute `var` using say, Monte Carlo
  string fname = out_fname + (string)".values";
  ofstream fout(fname.c_str());
  PrintValue(fout,"Total Values", var);

}

From another file:

template <class T>
void PrintValue(ofstream & fout, string s, T v) {
  fout << s;
  for(int i=0; i<48-s.size(); i++) {
    fout << '.';
  }
  fout << " " << v << endl;
}

Before implementing that loop, computeB just outputted one file of values. I now want it to create multiple values. So if it originally created a file called "output.values", how can I write a loop so that it creates "output1.values", "output2.values", ..., "output9.values"?

EDIT: I forgot to mention that the original code used the PrintValue function to output the values. I originally tried to save space and exclude this, but I just caused confusion

Answer 1

Disregarding all the syntax errors in your code ...

1. Use the input value i to compute the output file name.
2. Use the file name to construct an ofstream .
3. Use the ofstream to write var to.

Here's what the function will look like:

void combuteB(int i)
{
   char filename[100];
   sprintf(filename, "output%d.values", i);
   ofstream fout(filename);
   fout << "total values";
   fout << " " << var << endl;  // Not sure where you get 
                                // var from. But then, your
                                // posted code is not
                                // exactly clean.
}

Answer 2

You can use std::to_string() to convert from an int to a string :

void computeB(int i)
{
  if (std::ofstream fout("output" + std::to_string(i) + ".values"))
      fout << "total values" << " " << var << '\n';
  else
      throw std::runtime_error("unable to create output file");
}