reindex()

template<concepts::projection_map auto Projections, concepts::product_type T>

auto kumi::reindex ( T && t )

inlinenodiscardconstexpr

Reindex elements of a kumi::product_type.

This will issue a compile time error if any Idx is outside [0, size_v<T>[.

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

Note

Nothing prevent the number of reordered index to be lesser or greater than t size or the fact they can appear multiple times.

Template Parameters

Projections

A kumi::projection_map representing the reindexed slot of the elements

Parameters

t	kumi::product_type to reindex

Returns

A potentially nested tuple following the Indexes order

Helper type

namespace kumi::result
{
  template<product_type T, index_map auto Idxs> struct reindex;
 
  template<product_type T, index_map auto Idxs>
  using reindex_t= typename reindex<T,Idxs>::type;
}

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

Examples:

Tuple:

#include <kumi/kumi.hpp>
#include <iostream>
 
int main()
{
  using namespace kumi::literals;
  auto values = kumi::tuple { 1, 'a', 0.1 };
 
  constexpr auto basic = kumi::indexes(2_c,1_c,0_c);
  constexpr auto stack = kumi::projection_map(2_c,1_c,0_c, kumi::indexes(0_c,1_c,2_c));
  constexpr auto pairs = kumi::projection_map(kumi::indexes(0_c,0_c), kumi::indexes(1_c,1_c));
  
  std::cout << values << "\n";
  std::cout << kumi::reindex<basic>(values) << "\n";
  std::cout << kumi::reindex<stack>(values) << "\n";
  std::cout << kumi::reindex<pairs>(values) << "\n";
}

Record:

#include <kumi/kumi.hpp>
#include <iostream>
 
int main()
{
  using namespace kumi::literals;
  auto values = kumi::record { "a"_id = 1, "b"_id = 'a', "c"_id = 0.1 };
 
  constexpr auto basic = kumi::indexes(2_c,1_c,0_c);
  
  std::cout << values << "\n";
  std::cout << kumi::reindex<basic>(values) << "\n";
}