hum de dum III

#include <algorithm>    // std::for_each
#include <iostream>     // std::wcout, std::endl
#include <iterator>     // std::ostream_iterator
#include <stddef.h>     // ptrdiff_t
#include <stdexcept>    // std::exception, std::runtime_error
#include <stdlib.h>     // EXIT_SUCCESS, EXIT_FAILURE
#include <string>       // std::string, std::wstring
#include <utility>      // std::begin, std::end
#include <vector>       // std::vector

using namespace std;
typedef ptrdiff_t   Size;

bool throwX( string const& s ) { throw runtime_error( s ); }

template< class C >
auto rbegin( C& c ) -> decltype( c.rbegin() ) { return c.rbegin(); }

template< class C >
auto rend( C& c ) -> decltype( c.rend() ) { return c.rend(); }

template< class Elem >
void operator+=( vector<Elem>& v, Elem&& newElem )
{
    v.emplace_back( move( newElem ) );
}

namespace growDirection { enum Enum{ prepend, append }; }
namespace patternType { enum Enum { pure, gray }; }

struct Options
{
    growDirection::Enum     direction;
    patternType::Enum       type;

    Options(): direction(), type() {}

    Options( int const argc, char const* const argv[] )
        : direction()
        , type()
    {
        for( int i = 1;  i < argc;  ++i )
        {
            if( string( argv[i] ) == "-append" )
            {
                direction = growDirection::append;
            }
            else if( string( argv[i] ) == "-reflect" )
            {
                type = patternType::gray;
            }
            else
            {
                throwX( string() + "Usage: " + argv[0] + " [-reflect][-append]" );
            }
        }
    }
};

template< class It >
void addExtendedStringsTo(
    vector<wstring>&    result,
    wchar_t const       d,
    It const            itSourceBegin,
    It const            itSourceEnd,
    growDirection::Enum direction
    )
{
    for_each( itSourceBegin, itSourceEnd, [&]( wstring const& s )
    {
        result += (direction == growDirection::append? s + d : d + s);
    } );
}

vector<wstring> extended( vector<wstring> const& patterns, Options const& opt )
{
    vector<wstring> result;

    addExtendedStringsTo(
        result, L'0', begin( patterns ), end( patterns ), opt.direction
        );

    switch( opt.type )
    {
    case patternType::pure:
        addExtendedStringsTo(
            result, L'1', begin( patterns ), end( patterns ), opt.direction
            );
        break;
    case patternType::gray:
        addExtendedStringsTo(
            result, L'1', rbegin( patterns ), rend( patterns ), opt.direction
            );
    }
    return result;
}

void display( vector<wstring> const& patterns )
{
    for( auto it = begin( patterns); it != end( patterns ); ++it )
    {
        if( it > begin( patterns ) ) { wcout << L" "; }
        wcout << *it;
    }
    wcout << endl;
}

void cppMain( Options const& options )
{
    vector<wstring>     patterns( 1, L"" );

    for( int i = 1;  i <= 3;  ++i )
    {
        patterns = extended( patterns, options );
        display( patterns );
    }
}

int main( int argc, char* argv[] )
{
    try
    {
        cppMain( Options( argc, argv ) );
        return EXIT_SUCCESS;
    }
    catch( exception const& x )
    {
        wcerr << "!" << x.what() << endl;
    }
    return EXIT_FAILURE;
}