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#pragma once
namespace saw {
template <class T, class... TL> struct parameter_pack_index;
template <class T, class... TL> struct parameter_pack_index<T, T, TL...> {
static constexpr size_t value = 0u;
};
template <class T, class TL0, class... TL>
struct parameter_pack_index<T, TL0, TL...> {
static constexpr size_t value =
1u + parameter_pack_index<T, TL...>::value;
};
template <size_t N, class... T> struct parameter_pack_type;
template <class TN, class... T> struct parameter_pack_type<0, TN, T...> {
using type = TN;
};
template <size_t N, class TN, class... T>
struct parameter_pack_type<N, TN, T...> {
static_assert(sizeof...(T) > 0, "Exhausted parameters");
using type = typename parameter_pack_type<N - 1, T...>::type;
};
/*
* Nightmare inducing compiler problems found here. Somehow non-type
* string_literals cannot be resolved as non-type primitive template values can.
* This is the workaround
*/
template <string_literal V, string_literal Key0, string_literal... Keys>
struct parameter_key_pack_index_helper {
static constexpr size_t value =
(V == Key0)
? (0u)
: (1u + parameter_key_pack_index_helper<V, Keys...>::value);
};
template <string_literal V, string_literal Key0>
struct parameter_key_pack_index_helper<V, Key0> {
static constexpr size_t value = (V == Key0) ? (0u) : (1u);
};
template <string_literal V, string_literal... Keys>
struct parameter_key_pack_index {
static constexpr size_t value =
parameter_key_pack_index_helper<V, Keys...>::value;
static_assert(value < sizeof...(Keys),
"Provided string_literal doesn't exist in searched list");
};
}
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