Functor.hpp

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#ifndef META_FUNCTION_HPP_
#define META_FUNCTION_HPP_
 
#include "capymeta/concepts/Trait.hpp"
#include "capymeta/primitives/FixTemplateMetaArity.hpp"
#include "capymeta/primitives/MetaArity.hpp"
#include "capymeta/primitives/Pack.hpp"
 
#include <array>
#include <functional>
 
namespace capy::meta
{
 
template<
    auto Functor_,
    MetaArity REQUIRED_ARITY,
    MetaArity... OPTIONAL_ARITIES
>
struct functor_ft
{
public:
    static constexpr std::array META_CALLABLE_TAGS = { 
        MetaCallableTag::TYPE_CALLABLE 
    };
 
    static constexpr std::array META_CALLABLE_ARITIES = {
        REQUIRED_ARITY,
        OPTIONAL_ARITIES...
    };
    
public:
    template<typename... Args>
        requires std::invocable<decltype(Functor_), Pack<Args...>>
    struct Functor
    {
    public:
        using type = std::invoke_result_t<decltype(Functor_), Pack<Args...>>;
    };
 
public:
    template<MetaArity ARITY>
    using as_nary = fix_template_arity_ft<ARITY, Functor>;
 
    using as_unary = as_nary<MetaArity::N1>;
};
 
template<
    auto Functor_,
    MetaArity REQUIRED_ARITY,
    MetaArity... OPTIONAL_ARITIES
>
struct functor_fv
{
public:
    static constexpr std::array META_CALLABLE_TAGS = { 
        MetaCallableTag::TYPE_CALLABLE,
        MetaCallableTag::VALUE_CALLABLE
    };
    
    static constexpr std::array META_CALLABLE_ARITIES = {
        REQUIRED_ARITY,
        OPTIONAL_ARITIES...
    };
 
public:
    template<typename... Args>
        requires std::invocable<decltype(Functor_), Pack<Args...>>
    struct Functor
    {
    private:
        using ReturnType = std::invoke_result_t<decltype(Functor_), Pack<Args...>>;
    
    public:
        using type = ReturnType;
 
    public:
        static constexpr ReturnType value = std::invoke(
            Functor_,
            Pack<Args...>{}
        );
    };
 
public:
    template<MetaArity ARITY>
    using as_nary = fix_template_arity_fv<ARITY, Functor>;
 
    using as_unary = as_nary<MetaArity::N1>;
};
 
}
 
#endif // !META_FUNCTION_HPP_