Int sequence : generate « STL Algorithms Modifying sequence operations « C++ Tutorial

1. C++ Tutorial
2. STL Algorithms Modifying sequence operations
3. generate

/* The following code example is taken from the book
 * "The C++ Standard Library - A Tutorial and Reference"
 * by Nicolai M. Josuttis, Addison-Wesley, 1999
 *
 * (C) Copyright Nicolai M. Josuttis 1999.
 * Permission to copy, use, modify, sell and distribute this software
 * is granted provided this copyright notice appears in all copies.
 * This software is provided "as is" without express or implied
 * warranty, and with no claim as to its suitability for any purpose.
 */
#include <iostream>
#include <list>
#include <algorithm>

using namespace std;

/* PRINT_ELEMENTS()
 * - prints optional C-string optcstr followed by
 * - all elements of the collection coll
 * - separated by spaces
 */
template <class T>
inline void PRINT_ELEMENTS (const T& coll, const char* optcstr="")
{
    typename T::const_iterator pos;

    std::cout << optcstr;
    for (pos=coll.begin(); pos!=coll.end(); ++pos) {
        std::cout << *pos << ' ';
    }
    std::cout << std::endl;
}


class IntSequence {
  private:
    int value;
  public:
    // constructor
    IntSequence (int initialValue) : value(initialValue) {
    }

    // ''function call''
    int operator() () {
        return value++;
    }
};

int main()
{
    list<int> coll;

    // insert values from 1 to 9
    generate_n (back_inserter(coll),    // start
                9,                      // number of elements
                IntSequence(1));        // generates values

    PRINT_ELEMENTS(coll);

    // replace second to last element but one with values starting at 42
    generate (++coll.begin(),           // start
              --coll.end(),             // end
              IntSequence(42));         // generates values

    PRINT_ELEMENTS(coll);
}

1 2 3 4 5 6 7 8 9
1 42 43 44 45 46 47 48 9