feature_list< FEATURES > Struct Template Reference

#include <runtime_type.h>

Detailed Description

template<typename... FEATURES>
struct density::feature_list< FEATURES >

Type-list class template that can be used to specify which features a runtime_type captures from the target type.

Each type in the template arguments is either:

• a type satisfying the requirements of TypeFeature, like a built-in type feature (f_size, f_alignment, f_default_construct, f_copy_construct, f_move_construct, f_destroy, f_hash, f_rtti, f_equal, f_less, f_istream, f_ostream), or a user defined type feature.
• a nested feature_list
• the special tag type f_none

    using FewFeatures = feature_list<f_size, f_alignment>;
    using MoreFeatures = feature_list<FewFeatures, f_default_construct, f_copy_construct, f_move_construct, f_destroy>;
    using ManyFeatures = feature_list<MoreFeatures, f_equal, f_less, f_hash>;

feature_list provides a template alias to an std::tuple. An instance of this tuple is a pseudo-vtable associated to the target type.

    static_assert(std::is_same<
        FewFeatures::tuple_type, 
        std::tuple<f_size, f_alignment>>::value, "");

For the composition of the tuple:

• nested features are flatened
• duplicates are removed (only the first occurrence of a feature is considered)
• any occurrence of the pseudo-feature f_none is stripped out

    static_assert(std::is_same<
        ManyFeatures::tuple_type, std::tuple<
            f_size, f_alignment,
            f_default_construct, f_copy_construct, f_move_construct, f_destroy,
            f_equal, f_less, f_hash
        >>::value, "");

Two feature lists are equivalent if they prduce the same feature tuple:

    // Features1, Features2 and Features3 are equivalent....
    using Features1 = feature_list<f_size, f_alignment, f_copy_construct>;
    using Features2 = feature_list< feature_list<f_size>, 
        feature_list<f_alignment, f_copy_construct>>;
    using Features3 = feature_list<
        feature_list<f_size, f_none>, feature_list<feature_list<f_none>>,
        feature_list<f_size, f_alignment, f_copy_construct, f_none, f_copy_construct, f_size>>;
        
    // ...because they produce the same tuple
    static_assert(std::is_same<Features1::tuple_type, Features2::tuple_type>::value, "");
    static_assert(std::is_same<Features2::tuple_type, Features3::tuple_type>::value, "");

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The documentation for this struct was generated from the following file:

• C:/projects/density/include/density/runtime_type.h