extract

extract_t kumi::extract {}

inlineconstexprnodiscardnoexcept

Callable object extracting a sub product type from a product type.

On record types, this function operates on elements as if they were ordered. The considered order is the order of declaration.

Note

This function will issue a compile time error if I0 and I1 do not verify that 0 <= I0 <= I1 <= size_v<T>.

Header file

#include <kumi/algorithm/extract.hpp>

Call Signature

template<product_type T, std::size_t I0, std::size_t I1>
constexpr auto extract(T && t, kumi::index_t<I0>, kumi::index_t<I1>) noexcept;  // 1

template<product_type T, std::size_t I0>
constexpr auto extract(T && t, kumi::index_t<I0>) noexcept;                      // 2

Parameters

• t: Product Type to extract elements from
• i0: Compile-time index of the first element to extract
• i1: Compile-time index past the last element to extract

Return value

• 1. A new product type containing the selected range of elements of t.
• 2. A new product type containing the selected elements of t using size_v<T> as the last index.

Helper type

    template<kumi::concepts::product_type T, std::size_t I0, std::size_t I1 = std::size_t(-1)> struct extract
    {
      using type = decltype(kumi::extract(std::declval<T>(), kumi::index_t<I0>{}, kumi::index_t<I1>{}));
    };
 
    template<kumi::concepts::product_type T, std::size_t I0> struct extract<T, I0>
    {
      using type = decltype(kumi::extract(std::declval<T>(), kumi::index_t<I0>{}));
    };
 
    template<kumi::concepts::product_type T, std::size_t I0, std::size_t I1 = std::size_t(-1)>
    using extract_t = typename kumi::result::extract<T, I0, I1>::type;
 

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

Examples

Tuple

#include <kumi/kumi.hpp>
#include <iostream>
 
int main()
{
  using namespace kumi::literals;
 
  kumi::tuple a = { 1, 2.3, 4.5f,'6',"7", short{89} };
 
  auto head = kumi::extract(a,0_c,1_c);
  auto mid  = kumi::extract(a,1_c,3_c);
  auto last = kumi::extract(a,kumi::index<3>);
 
  std::cout << a << " => " << head << ' '  << mid << ' ' << last << '\n';
}

Record

#include <kumi/kumi.hpp>
#include <iostream>
 
int main()
{
  using namespace kumi::literals;
 
  kumi::record a =  { "a"_id = 1, "b"_id = 2.3, "c"_id = 4.5f, "d"_id = '6'
                    , "e"_id = "7", "f"_id = short{89} };
 
  auto head = kumi::extract(a,0_c,1_c);
  auto mid  = kumi::extract(a,1_c,3_c);
  auto last = kumi::extract(a,kumi::index<3>);
 
  std::cout << a << " => " << head << ' '  << mid << ' ' << last << '\n';
}