Static Value Lists

// This file is part of the lobster library
// Copyright: Andreas Raczek
// This file is published under the The Code Project Open License (CPOL) 
// See the file "CPOL.html" for the full license governing this code. 
#pragma once

namespace lobster {

namespace static_list {

template<typename list, bool compact> struct compact_helper;

// compact_helper<..., false> does not combine this list item with the parent list item
template<
    typename list
> struct compact_helper<
    list,
    false
> {
    typedef list type;
};


// compact_helper<..., false> does not combine this list item with the parent list item
template<
    typename grandparent,
    typename grandparent::value_type parent_value_first,
    typename grandparent::value_type parent_value_last,
    typename grandparent::value_type value_first,
    typename grandparent::value_type value_last
> struct compact_helper<
    list_item<
        list_item<
            grandparent, 
            parent_value_first, 
            parent_value_last 
        >,
        value_first,
        value_last
    >,
    true
> {
    typedef list_item<grandparent, parent_value_first, value_last> type;
};


template<typename list> struct compact;


template<
    typename grandparent,
    typename grandparent::value_type parent_value_first,
    typename grandparent::value_type parent_value_last,
    typename grandparent::value_type value_first,
    typename grandparent::value_type value_last
> struct compact<
    list_item<
        list_item<
            grandparent, 
            parent_value_first, 
            parent_value_last 
        >,
        value_first,
        value_last
    >
> {
    typedef typename grandparent::value_type value_type;
    typedef list_item<grandparent, parent_value_first, parent_value_last> parent;
    
    typedef typename compact<parent>::type compacted_parent;
    
    // The compacted parent may have new first and last elements, see how it fits:
    const static bool fits_ascending = 
        ((int) (compacted_parent::value_first) <= (int) (compacted_parent::value_last)) && 
        ((int) (value_first) <= (int) (value_last)) && 
        ((int) (value_first) == ((int) (compacted_parent::value_last) + 1));
        
    const static bool fits_descending = 
        ((int) (compacted_parent::value_first) >= (int) (compacted_parent::value_last)) && 
        ((int) (value_first) >= (int) (value_last)) && 
        ((int) (value_first) == ((int) (compacted_parent::value_last) - 1));
        
    // For both fitting types, the entries are combined
    typedef typename compact_helper<
        list_item<compacted_parent, value_first, value_last>,
        fits_ascending || fits_descending
    >::type type;
};


template<
    typename value_type,
    value_type value_first,
    value_type value_last
> struct compact<
    list_item<
        list_tail<
            value_type
        >,
        value_first,
        value_last
    >
> {
    typedef list_item<list_tail<value_type>, value_first, value_last> type;    
};


}

}