C++ Tutorial/File Stream/istream iterator

Create istream_iterator for reading int values from cin

<source lang="cpp">#include <iostream> using std::cout; using std::cin; using std::endl;

1. include <iterator>

int main() {

  cout << "Enter two integers: ";
  std::istream_iterator< int > inputInt( cin );
  int number1 = *inputInt; 
  ++inputInt;              
  int number2 = *inputInt; 
  std::ostream_iterator< int > outputInt( cout );
  cout << "The sum is: ";
  *outputInt = number1 + number2;
  cout << endl;
  return 0;

}</source>

Enter two integers: 1 2
The sum is: 3

Use istreambuf_iterator, ostreambuf_iterator, and replace_copy() to filter a file.

<source lang="cpp">#include <iostream>

1. include <fstream>
2. include <iterator>
3. include <algorithm>

using namespace std; int main(int argc, char *argv[]) {

 if(argc != 5) {
   cout << "Usage: replace in out oldchar newchar\n";
   return 1;
 }
 ifstream in(argv[1]);
 ofstream out(argv[2]);
 if(!in.is_open()) {
   cout << "Cannot open input file.\n";
   return 1;
 }
 if(!out.is_open()) {
   cout << "Cannot open output file.\n";
   return 1;
 }
 // Create stream iterators.
 istreambuf_iterator<char> in_itr(in);
 ostreambuf_iterator<char> out_itr(out);
 // Copy the file, replacing characters in the process.
 replace_copy(in_itr, istreambuf_iterator<char>(),out_itr, *argv[3], *argv[4]);
 in.close();
 out.close();
 return 0;

}</source>

Use istream_iterator

<source lang="cpp">#include <iostream>

1. include <iterator>

using namespace std; int main() {

 istream_iterator<char> in_it(cin);
 do {
   cout << *in_it++;
 } while (*in_it != "."); 
 return 0;

}</source>

a
a
aa
aa
aa
aa
aaaaaaa^CTerminate batch job (Y/N)? n

Use istream_iterator and ostream_iterator to read from cin and write to cout.

<source lang="cpp">#include <iostream>

1. include <iterator>
2. include <string>
3. include <vector>

using namespace std; int main() {

 unsigned i;
 double d;
 string str;
 vector<int> vi;
 vector<double> vd;
 vector<string> vs;
 cout << "Enter some integers, enter 0 to stop.\n";
 istream_iterator<int> int_itr(cin);
 do {
   i = *int_itr; 
   if(i != 0) {
     vi.push_back(i); 
     ++int_itr; 
   }
 } while (i != 0);
 cout << "Enter some doubles, enter 0 to stop.\n";
 istream_iterator<double> double_itr(cin);
 do {
   d = *double_itr;
   if(d != 0.0) {
     vd.push_back(d); 
     ++double_itr; 
   }
 } while (d != 0.0);
 cout << "Enter some strings, enter "quit" to stop.\n";
 istream_iterator<string> string_itr(cin);
 do {
   str = *string_itr; 
   if(str != "quit") {
     vs.push_back(str);
     ++string_itr;
   }
 } while (str != "quit");
 cout << endl;
 cout << "Here is what you entered:\n";
 for(i=0; i < vi.size(); i++) cout << vi[i] << " ";
 cout << endl;
 for(i=0; i < vd.size(); i++) cout << vd[i] << " ";
 cout << endl;
 for(i=0; i < vs.size(); i++) cout << vs[i] << " ";

 // Now, use ostream_iterator to write to cout.
 // Create an output iterator for string.
 ostream_iterator<string> out_string_itr(cout);
 *out_string_itr = "\n";
 *out_string_itr = string("\nThis is a string\n");
 *out_string_itr = "This is too.\n";
 // Create an output iterator for int.
 ostream_iterator<int> out_int_itr(cout);
 *out_int_itr = 10;
 *out_string_itr = " ";
 *out_int_itr = 15;
 *out_string_itr = " ";
 *out_int_itr = 20;
 *out_string_itr = "\n";
 // Create an output iterator for bool.
 ostream_iterator<bool> out_bool_itr(cout);
 *out_bool_itr = true;
 *out_string_itr = " ";
 *out_bool_itr = false;
 return 0;

}</source>