contains

contains_t kumi::contains {}

inlineconstexprnodiscardnoexcept

Callable object checking if a product type contains a given identifier.

Header file

#include <kumi/algorithm/contains.hpp>

Call Signature

template<product_type T, identifier ID>
constexpr auto contains(T && t, ID const& id) noexcept;

Parameters

• t: The product type to inspect
• id: The identifier to check for

Return value

• std::true_type if t contains a field labeled with the id identifier, std::false_type otherwise.

Helper type

    template<kumi::concepts::product_type T, kumi::concepts::identifier ID> struct contains
    {
      using type = decltype(kumi::contains(std::declval<T>(), std::declval<ID>()));
    };
 
    template<kumi::concepts::product_type T, kumi::concepts::identifier ID>
    using contains_t = typename kumi::result::contains<T, ID>::type;
 

Computes the return type of a call to kumi:contains:

Examples

Tuple

#include <kumi/kumi.hpp>
#include <iostream>
 
using namespace kumi::literals;
 
template<kumi::concepts::product_type T>
void check_contains(T const& t)
{
  if constexpr(kumi::contains(T{}, "value"_id))
    std::cout << "Correct product_type: " << get<"value"_id>(t) << '\n';
  else
    std::cout << "Incorrect product type\n";
}
 
int main()
{
  check_contains( kumi::tuple{"value"_id = 9  });
  check_contains( kumi::tuple{"malus"_id = 3.5});
  check_contains( kumi::tuple{"malus"_id = 6.5, "value"_id = 17} );
}

Record

#include <kumi/kumi.hpp>
#include <iostream>
 
using namespace kumi::literals;
 
template<kumi::concepts::product_type T>
void check_contains(T const& t)
{
  if constexpr(kumi::contains(T{}, "value"_id))
    std::cout << "Correct product_type: " << get<"value"_id>(t) << '\n';
  else
    std::cout << "Incorrect product type\n";
}
 
int main()
{
  check_contains( kumi::record{"value"_id = 9  });
  check_contains( kumi::record{"malus"_id = 3.5});
  check_contains( kumi::record{"malus"_id = 6.5, "value"_id = 17} );
}