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99 Bottles Of Beer, using Boost MPL

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#include <boost/mpl/assert.hpp>

#include <boost/mpl/at.hpp>

#include <boost/mpl/back_inserter.hpp>

#include <boost/mpl/copy.hpp>

#include <boost/mpl/divides.hpp>

#include <boost/mpl/empty_sequence.hpp>

#include <boost/mpl/equal.hpp>

#include <boost/mpl/equal_to.hpp>

#include <boost/mpl/fold.hpp>

#include <boost/mpl/for_each.hpp>

#include <boost/mpl/if.hpp>

#include <boost/mpl/joint_view.hpp>

#include <boost/mpl/less.hpp>

#include <boost/mpl/minus.hpp>

#include <boost/mpl/modulus.hpp>

#include <boost/mpl/push_back.hpp>

#include <boost/mpl/range_c.hpp>

#include <boost/mpl/string.hpp>

#include <boost/mpl/transform.hpp>

#include <boost/mpl/vector.hpp>

 

#include <iostream>

 

using namespace boost::mpl;

 

template <typename n>

struct NumberInEnglish

{

    // Can't handle >= 100

    BOOST_MPL_ASSERT(( less<n, int_<100> > ));

 

    typedef int_<10> ten;

    typedef int_<20> twenty;

    typedef char_<'-'> dash;

 

    typedef vector<

        string<>, // use Ones vector

        string<>, // use Teens vector

        string<'twen','ty'>,

        string<'thir','ty'>,

        string<'four','ty'>,

        string<'fift','y'>,

        string<'sixt','y'>,

        string<'seve','nty'>,

        string<'eigh','ty'>,

        string<'nine','ty'> > Tens;

 

    typedef vector<

        string<'no ','more'>,

        string<'one'>,

        string<'two'>,

        string<'thre','e'>,

        string<'four'>,

        string<'five'>,

        string<'six'>,

        string<'seve','n'>,

        string<'eigh','t'>,

        string<'nine'>

        > Ones;

 

    typedef vector<

        string<'ten'>,

        string<'elev','en'>,

        string<'twel','ve'>,

        string<'thir','teen'>,

        string<'four','teen'>,

        string<'fift','een'>,

        string<'sixt','een'>,

        string<'seve','ntee','n'>,

        string<'eigh','teen'>,

        string<'nine','teen'>

        > Teens;

 

    typedef if_<

        modulus<n, ten>,

        typename copy<

            joint_view<

                typename push_back<typename at<Tens, divides<n, ten> >::type, dash>::type,

                typename at<Ones, modulus<n, ten> >::type>,

            back_inserter<string<> >

            >::type,

        typename at<Tens, divides<n, ten> >::type

        > DoubleDigit;

 

    typedef typename if_<

        less<n, ten>,

        typename at<Ones, n>::type,

        typename if_<

            less<n, twenty>,

            typename at<Teens, minus<n, ten> >::type,

            typename DoubleDigit::type

        >::type

    >::type type;

};

 

BOOST_MPL_ASSERT(( equal< NumberInEnglish<int_<4> >::type, string<'four'> > ));

BOOST_MPL_ASSERT(( equal< NumberInEnglish<int_<14> >::type, string<'four','teen'> > ));

BOOST_MPL_ASSERT(( equal< NumberInEnglish<int_<20> >::type, string<'twen','ty'> > ));

BOOST_MPL_ASSERT(( equal< NumberInEnglish<int_<44> >::type, string<'four','ty-f','our'> > ));

 

template <typename n>

struct CountBottles

{

    typedef string<'bott','le'> Bottle;

 

    typedef typename copy<

        joint_view<

            typename push_back<

                typename NumberInEnglish<n>::type, char_<' '> >::type,

            typename if_<

                equal_to<n, int_<1> >,

                Bottle,

                push_back<Bottle, char_<'s'> >::type

                >::type

            >,

        back_inserter<string<> >

        >::type type;

};

 

BOOST_MPL_ASSERT(( equal< CountBottles<int_<0> >::type, string<'no m','ore ','bott','les'> > ));

BOOST_MPL_ASSERT(( equal< CountBottles<int_<1> >::type, string<'one ','bott','le'> > ));

BOOST_MPL_ASSERT(( equal< CountBottles<int_<14> >::type, string<'four','teen',' bot','tles'> > ));

 

template <typename n>

struct Verse

{

    typedef string<'\n'> NL;

    typedef string<',\n'> CommaNL;

    typedef string<' of ','beer'> OfBeer;

    typedef string<' on ','the ','wall'> OnTheWall;

    typedef string<'take',' one',' dow','n, p','ass ','it a','roun','d,\n'> TakeOneDownPassItAround;

 

    typedef typename transform<

        vector<

            typename CountBottles<n>::type,

            OfBeer,

            OnTheWall,

            CommaNL,

            typename CountBottles<n>::type,

            OfBeer,

            CommaNL,

            TakeOneDownPassItAround,

            typename CountBottles<typename prior<n>::type>::type,

            OfBeer,

            NL,

            NL

            >,

        c_str<_1>

        >::type strings;

};

 

struct PrintValue

{

    PrintValue(std::ostream& os) : os_(os) {}

    std::ostream& os_;

 

    template <typename T>

    void operator() (T t)

    {

        os_ << T::value;

    }

};

 

template <typename n>

std::ostream& operator<< (std::ostream& os, Verse<n> verse)

{

    boost::mpl::for_each<typename Verse<n>::strings>(PrintValue(os));

};

 

struct PrintTo

{

    PrintTo(std::ostream& os) : os_(os) {}

    std::ostream& os_;

 

    template <typename T>

    void operator() (T t)

    {

        os_ << t;

    }

};

 

int main()

{

    boost::mpl::for_each<

        range_c<int, 1, 100>,

        lambda<

            Verse<minus<int_<100>, _1> >

            >::type>(

                PrintTo(std::cout));

 

    return 0;

}
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