exclusive_scan_left() [2/2]

template<concepts::monoid M, concepts::sized_product_type_or_more< 1 > T>

auto kumi::exclusive_scan_left ( M && m, T && t )

inlinenodiscardconstexpr

Computes the exclusive prefix 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 identity of the provided monoid.

Parameters

m	Monoid callable function to apply
t	Product type to operate on

Returns

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

Helper type

namespace kumi::result
{
  template<typename Function, product_type T> struct exclusive_scan_left;
 
  template<typename Function, product_type T>
  using exclusive_scan_left_t = typename exclusive_scan_left<Function,T>::type;
}

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

Examples:

Tuple:

#include <kumi/kumi.hpp>
#include <iostream>
 
int main()
{
  auto t = kumi::tuple{2.,1,short{55},'z'};
 
  auto output = kumi::exclusive_scan_left( [](auto acc, auto elt) 
                  { 
                    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_left(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_left( [](auto acc, auto elt) 
                  { 
                    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_left(kumi::function::plus, u) << "\n";
}