exclusive_scan_right() [1/2]

template<typename Function, concepts::product_type T, typename Value>

auto kumi::exclusive_scan_right ( Function f, T && t, Value init )

inlinenodiscardconstexpr

Computes the exclusive suffix scan of all elements of a product type using a tail recursive call.

On record types, this function operates on the underlying values, not on the fields themselves.

Note

The first stored value is the provided initial value.

Parameters

f	Binary callable function to apply
t	Product type to operate on
init	Optional initial value of the scan

Returns

A tuple of suffix partial accumulations where each element 'I' equals f( f( f(init, get<0>(t)), ...), get<I-1>(t))

Helper type

namespace kumi::result
{
  template<typename Function, product_type T, typename Value> struct exclusive_scan_right;
 
  template<typename Function, product_type T, typename Value>
  using exclusive_scan_right_t = typename exclusive_scan_right<Function,T,Value>::type;
}

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

Examples:

Tuple:

#include <kumi/kumi.hpp>
#include <iostream>
 
int main()
{
  auto t = kumi::tuple{2.,1,short{55},'z'};
 
  auto output = kumi::exclusive_scan_right( [](auto elt, auto acc) 
                  { 
                    return acc + sizeof(elt); 
                  }
                  , t
                  , std::size_t{42}                
                );
 
  std::cout << output << "\n"; 
 
  auto u = kumi::tuple{1,3,2,4,0,5,9,6,7};
 
  std::cout << kumi::exclusive_scan_right(kumi::function::plus, u) << "\n";
}

Record:

#include <kumi/kumi.hpp>
#include <iostream>
 
int main()
{
  using namespace kumi::literals;
  auto r = kumi::record{"a"_id = 2.,"b"_id = 1,"c"_id = short{55},"d"_id = 'z'};
 
  auto output = kumi::exclusive_scan_right( [](auto elt, auto acc) 
                  { 
                    return acc + sizeof(elt); 
                  }
                  , r
                  , std::size_t{42}                
                );
 
  std::cout << output << "\n"; 
 
  auto u = kumi::record{"a"_id = 1,"b"_id = 3,"c"_id = 2,"d"_id = 4,"e"_id = 0
                      , "f"_id = 5,"g"_id = 9,"h"_id = 6,"i"_id = 7};
 
  std::cout << kumi::exclusive_scan_right(kumi::function::plus, u) << "\n";
}