front()

template<concepts::non_empty_product_type T>

decltype(auto) kumi::front ( T && t )

inlinenodiscardconstexpr

Retrieves the front of a product type.

Parameters

t	Base product type

Returns

A reference to the first element of the product type t.

Note

This function does not take part in overload resolution if t is an empty product type.

Helper type

namespace kumi::result
{
  template<product_type T> struct front;
 
  template<product_type T>
  using front_t = typename front<T>::type;
}

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

Examples:

Tuple:

#include <kumi/kumi.hpp>
#include <iostream>
 
int main()
{
  kumi::tuple x{2.3,18, 5.f};
 
  std::cout << kumi::front(x) << "\n";
  std::cout << kumi::back(x)  << "\n";
 
  kumi::front(x) = 98.5;
  kumi::back(x)  = 66.f;
 
  std::cout << x << "\n";
}

Record:

#include <kumi/kumi.hpp>
#include <iostream>
 
int main()
{
  using namespace kumi::literals;
 
  kumi::record x{"a"_id = 2.3,"b"_id = 18, "c"_id = 5.f};
 
  std::cout << kumi::front(x) << "\n";
  std::cout << kumi::back(x)  << "\n";
 
  kumi::front(x) = 98.5;
  kumi::back(x)  = 66.f;
 
  std::cout << x << "\n";
}