Practice 1

namespace {
    //show
    template <typename T>
    class show {
    public:
        void operator() (T n) {
            cout << n << " ";
        }
    };
}

Practice 2

namespace{
    template <typename T>
    struct show : public unary_function<T, void> {
        void operator() (T n) {
            cout << n << " ";
        }
    };
}

Practice 3

namespace {
    //out() algorithm
    template <typename InputIterator, typename T>
    void out(InputIterator first, InputIterator last) {
        for_each(first, last, show<T>());
        cout << endl;
    }
}

Practice 4

#include <iostream>
#include <string>
#include <functional>    // for funciton object
#include <algorithm>     // for out() algorithm
#include <vector> 

using namespace std;

// define show function object and out()
namespace {
    //show
    template <typename T>
    struct show : public unary_function<T, void> {
        void operator() (T n) {
            cout << n << " ";
        }
    };

    //out() algorithm
    template <typename InputIterator, typename T>
    void out(InputIterator first, InputIterator last) {
        for_each(first, last, show<T>());
        cout << endl;
    }
}

int main() {
    string strarray[] = {"a", "c", "l", "u", "w", "e", "c",
        "z", "b", "l", "o", "r"};
    int size = sizeof strarray / sizeof(string);

    vector<string> v1(size);
    v1.assign(strarray, strarray + size);
    out<vector<string>::iterator, string>(v1.begin(), v1.end());

    sort(v1.begin(), v1.end());
    out<vector<string>::iterator, string>(v1.begin(), v1.end());

    sort(v1.begin(), v1.end(), greater<string>());
    out<vector<string>::iterator, string>(v1.begin(), v1.end());

    return 0;
}