CPPTM Answers - Exercise 7-8

Here's code:

 
//solution to excercise 7.8 using transform_view
#include <boost/mpl/pair.hpp>
#include <boost/mpl/transform_view.hpp>
#include <boost/mpl/range_c.hpp>
#include <boost/mpl/for_each.hpp>
#include <iostream>
#include <boost/test/unit_test.hpp>

namespace boost{namespace mpl{

  template<class Row, class Column>
  struct
row_column_view
  : pair<Row,Column>
{
        typedef
      row_column_view
    type
    ;
    static void print(void)
    {
        std::cout<<"row.col="<<Row::value<<"."<<Column::value<<"\n";
    }
    
};

  template<class Row, class Columns>
  struct
row_view
  : transform_view<Columns,row_column_view<Row, arg<1> > >::type
{
        typedef
      row_view
    type
    ;
    
    struct element_printer
    {
        template<class RowColumnView>
        void operator()(RowColumnView)
        {
            RowColumnView::print();

        }
    };
    
};

  template<class Rows, class Columns>
  struct
cross_product_view
  : transform_view<Rows, row_view<arg<1>, Columns> >::type
{
    struct element_printer
    {
        template<class RowView>
        void operator()(RowView)
        {
            typedef RowView view_type;
            typename view_type::element_printer a_printer;
            for_each<view_type>(a_printer);
        }
    };
    
    static void print(void)
    {
        typedef cross_product_view view_type;
        typename view_type::element_printer a_printer;
        for_each<view_type>(a_printer);
    }
    
};

}}//exit boost::mpl namespace

using namespace boost;

void test(void)
{
    typedef mpl::range_c<int,0,3> cols_type;
    typedef mpl::range_c<int,100,104> rows_type;
    mpl::cross_product_view<cols_type,rows_type>::print();
}

void always_fail(void)
{
    BOOST_CHECK(false);
}

namespace butf = boost::unit_test_framework;
butf::test_suite* init_unit_test_suite(int argc, char* argv[])
{
    butf::test_suite* tests = BOOST_TEST_SUITE("exercise 7.8 tests");
    tests->add(BOOST_TEST_CASE(&test));
    tests->add(BOOST_TEST_CASE(&always_fail));
    return tests;
}

Here's output:

 
Running 2 test cases...
row.col=0.100
row.col=0.101
row.col=0.102
row.col=0.103
row.col=1.100
row.col=1.101
row.col=1.102
row.col=1.103
row.col=2.100
row.col=2.101
row.col=2.102
row.col=2.103
8.xform_view.cpp(86): error in "always_fail": test false failed

This solution by: Larry Evans ( cppljevans@cox-internet.com )