As @Mgetz says, you probably forgot to #include <fstream>. The reason you didn’t get a not declared error and instead this incomplete type not allowed error has to do with what happens when there is a type that has been “forward declared”, but not yet fully defined. Look at this example: Notice we could not actually instantiate a Foo object or … Read more
Yes, you can. That’s the point in the OO concept called subtype polymorphism. Since ofstream derives from ostream, every instance of ofstream is at the same time an instance of ostream too (conceptually). So you can use it wherever an instance of ostream is expected.
First, make an ifstream: The two standard methods are: Assume that every line consists of two numbers and read token by token:int a, b; while (infile >> a >> b) { // process pair (a,b) } Line-based parsing, using string streams:#include <sstream> #include <string> std::string line; while (std::getline(infile, line)) { std::istringstream iss(line); int a, b; if … Read more
First, make an ifstream: The two standard methods are: Assume that every line consists of two numbers and read token by token: int a, b; while (infile >> a >> b) { // process pair (a,b) } Line-based parsing, using string streams: #include <sstream> #include <string> std::string line; while (std::getline(infile, line)) { std::istringstream iss(line); int … Read more