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Passing Streams to Functions

Passing Streams to Functions. Passing Streams to Functions. One Rule: always pass a stream as a reference. file: fileopen.h // Pre: template parameter T must be either ifstream or ofstream type. template < typename T>

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Passing Streams to Functions

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  1. Passing Streams to Functions

  2. Passing Streams to Functions • One Rule: always pass a stream as a • reference

  3. file: fileopen.h // Pre: template parameter T must be either ifstream or ofstream type. template <typename T> void fileopen (T & filestr, const string promptpart) { const int MAX_TRIES = 5; int count = 0;     string filename; cout<<”enter name of “<<promptpart<<” file: “; cin>>filename; filestr.open(filename.c_str());     while (!filestr)     { filestr.clear(); // may be necessary on your platform cout<<”ERROR: file not connected. Try again...”<<endl; cout<<”enter name of “<<promptpart<<” file: “; cin>>filename; filestr.open(filename.c_str());         count++;         if (count > MAX_TRIES)         { cout<<”NOT CONNECTING AFTER “<<MAX_TRIES<<” ATTEMPTS...BAILING OUT” <<”...”<<endl;            exit(1);         }     } return; }

  4. #include <fstream> #include “fileopen.h” int main() { ifstream in; fileopen(in, “input”);

  5. Operator Overloading ostream& operator << (ostream & out, const point & p) { out << “(” << p.m_X << “, ” << p.m_Y << “)”; return out; }

  6. Operator Overloading ostream& operator << (ostream & out, const point & p) { out << “(” << p.m_X << “, ” << p.m_Y << “)”; return out; } // example 1 point p1, p2; cout << p1; cout << p1 << " “ << p2;

  7. Operator Overloading ostream& operator << (ostream & out, const point & p) { out << “(” << p.m_X << “, ” << p.m_Y << “)”; return out; } // example 1 point p1, p2; cout<< p1; cout << p1 << “ ” << p2; // example 2 ofstreamfout; fout << p1; fout << p1 << “ ” << p2;

  8. Chaining Stream Processing... // example 1 cout << p1 << “ ” << p2; ... ostream& operator << (ostream & out, const point & p) { out << “(” << p.m_X << “, ” << p.m_Y << “)”; return out; }

  9. Chaining Stream Processing... cout << p1 // example 1 cout << p1 << “ ” << p2; ... ostream& operator << (ostream & out, const point & p) { out << “(” << p.m_X << “, ” << p.m_Y << “)”; return out; }

  10. Chaining Stream Processing... cout << p1 executes overloaded operator<< // example 1 cout << p1 << “ ” << p2; ... ostream& operator << (ostream & out, const point & p) { out << “(” << p.m_X << “, ” << p.m_Y << “)”; return out; }

  11. Chaining Stream Processing... cout << p1 executes overloaded operator<< returns cout with the points data added to the stream // example 1 cout << p1 << “ ” << p2; ... ostream& operator << (ostream & out, const point & p) { out << “(” << p.m_X << “, ” << p.m_Y << “)”; return out; }

  12. Chaining Stream Processing... cout << p1 executes overloaded operator<< returns cout with the points data added to the stream cout << “ ” // example 1 cout << p1 << “ ” << p2; ... ostream& operator << (ostream & out, const point & p) { out << “(” << p.m_X << “, ” << p.m_Y << “)”; return out; }

  13. Chaining System Processing... cout << p1 executes overloaded operator<< returns cout with the points data added to the stream cout << “ ” returns cout with the space added to the stream // example 1 cout << p1 << “ ” << p2; ... ostream& operator << (ostream & out, const point & p) { out << “(” << p.m_X << “, ” << p.m_Y << “)”; return out; }

  14. Chaining Stream Processing... cout << p1 executes overloaded operator<< returns cout with the points data added to the stream cout << “ ” returns cout with the space added to the stream cout << p2 // example 1 cout << p1 << “ ” << p2; ... ostream& operator << (ostream & out, const point & p) { out << “(” << p.m_X << “, ” << p.m_Y << “)”; return out; }

  15. Chaining Stream Processing... cout << p1 executes overloaded operator<< returns cout with the points data added to the stream cout << “ ” returns cout with the space added to the stream cout << p2 executes overloaded operator<< // example 1 cout << p1 << “ ” << p2; ... ostream& operator << (ostream & out, const point & p) { out << “(” << p.m_X << “, ” << p.m_Y << “)”; return out; }

  16. Chaining Stream Processing... cout << p1 executes overloaded operator<< returns cout with the points data added to the stream cout << “ ” returns cout with the space added to the stream cout << p2 executes overloaded operator<< returns cout with the points data added to the stream // example 1 cout << p1 << “ ” << p2; ... ostream& operator << (ostream & out, const point & p) { out << “(” << p.m_X << “, ” << p.m_Y << “)”; return out; }

  17. Final Note iostream and fstream are of the same family getline, ignore, get, putback, etc are all available for filestreams as well! ifstream fin; char input; fin.open(“input.dat”); while (in.get(input)) { process_data(input);

  18. End of Session

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