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Front Page / Metafunctions / Miscellaneous / inherit_linearly

inherit_linearly

Synopsis

template<
      typename Types
    , typename Node
    , typename Root = empty_base
    >
struct inherit_linearly
    : fold<Types,Root,Node>
{
};

Description

A convenience wrapper for fold to use in the context of sequence-driven class composition. Returns the result the successive application of binary Node to the result of the previous Node invocation (Root if it's the first call) and every type in the Forward Sequence Types in order.

Header

#include <boost/mpl/inherit_linearly.hpp>

Model of

Metafunction

Parameters

Parameter Requirement Description
Types Forward Sequence Types to inherit from.
Node Binary Lambda Expression A derivation metafunction.
Root A class type A type to be placed at the root of the class hierarchy.

Expression semantics

For any Forward Sequence types, binary Lambda Expression node, and arbitrary class type root:

typedef inherit_linearly<types,node,root>::type r;
Return type:

A class type.

Semantics:

Equivalent to

typedef fold<types,root,node>::type r;

Complexity

Linear. Exactly size<types>::value applications of node.

Example

template< typename T > struct tuple_field
{
    T field;
};

template< typename T >
inline
T& field(tuple_field<T>& t)
{
    return t.field;
}

typedef inherit_linearly<
      vector<int,char const*,bool>
    , inherit< _1, tuple_field<_2> >
    >::type tuple;


int main()
{
    tuple t;

    field<int>(t) = -1;
    field<char const*>(t) = "text";
    field<bool>(t) = false;

    std::cout
        << field<int>(t) << 'n'
        << field<char const*>(t) << 'n'
        << field<bool>(t) << 'n'
        ;
}

See also

Metafunctions, Algorithms, inherit, empty_base, fold, reverse_fold