examples/manual/generate.cpp

/**************************************************************************
 *
 * generate.cpp - Example program for initializing a container with values 
 *                produced by a value-generator class.
 *
 * $Id: //stdlib/dev/examples/stdlib/manual/generate.cpp#12 $
 *
 ***************************************************************************
 *
 * Copyright (c) 1994-2005 Quovadx,  Inc., acting through its  Rogue Wave
 * Software division. Licensed under the Apache License, Version 2.0 (the
 * "License");  you may  not use this file except  in compliance with the
 * License.    You    may   obtain   a   copy   of    the   License    at
 * http://www.apache.org/licenses/LICENSE-2.0.    Unless   required    by
 * applicable law  or agreed to  in writing,  software  distributed under
 * the License is distributed on an "AS IS" BASIS,  WITHOUT WARRANTIES OR
 * CONDITIONS OF  ANY KIND, either  express or implied.  See  the License
 * for the specific language governing permissions  and limitations under
 * the License.
 * 
 **************************************************************************/

#include <algorithm>    // for generate, generate_n
#include <iostream>     // for cout, endl
#include <iterator>     // for ostream_iterator
#include <vector>	// for vector

#include <examples.h>


// Value generator simply doubles the current value and returns it.
template <class T>
class generator
{
    T val_;
public:
    generator (const T &val) : val_ (val) { }
    T operator() () {
        return val_ += val_;
    }
};


int main ()
{
    // Typedef for convenience.
    typedef std::vector<short, std::allocator<short> > Vector;

    Vector::value_type arr[4] = { 1, 2, 3, 4 };

    // Set up two vectors.
    Vector v1 (arr, arr + sizeof arr / sizeof *arr);
    Vector v2 = v1;

    // Set up one empty vector.
    Vector v3;

    // Create a generator function object.
    generator<Vector::value_type> gen (1);

    // Generate values for all of v1.
    std::generate (v1.begin (), v1.end (), gen);

    // Generate values for first 3 of v2.
    std::generate_n (v2.begin (), 3, gen);

    // Use back_insert_iterator to generate 5 values for v3.
    std::generate_n (std::back_inserter (v3), 5, gen);

    // Copy all three to cout.
    std::ostream_iterator<Vector::value_type,
                          char,
                          std::char_traits<char> > out (std::cout, " ");

    std::copy (v1.begin (), v1.end (), out);
    std::cout << std::endl;

    std::copy (v2.begin (), v2.end (), out);
    std::cout << std::endl;

    std::copy (v3.begin (), v3.end (), out);
    std::cout << std::endl;

    // Generate 3 values into cout.
    std::generate_n (out, 3, gen);
    std::cout << std::endl;

    return 0;
}