generate.cpp

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#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;
}