fetch()

template<concepts::keyword K, concepts::option... Os>

constexpr decltype(auto) rbr::fetch ( K const &  k, Os const &...  os  )

constexpr

Retrieved a value via a keyword.

Retrieve the value bound to a given keyword k inside a variadic list of rbr::options. If such a keyword is not present, either an instance of rbr::unknown_key is returned or a default value or function call will be returned.

Parameters

k	Keywords to check
os	Options to inspect

Returns

If any, the value bound to k.

Helper Types

namespace rbr::result
{
  template<auto Keyword, typename... Sources> struct fetch
 
  template<auto Keyword, typename... Sources>
  using fetch_t = typename fetch<Keyword,Sources...>::type;
}

Return the type of a call to rbr::fetch.

Example:

 
#include <raberu/raberu.hpp>
#include <iostream>
 
int main()
{
  using namespace rbr::literals;
 
  int i = 77;
 
  auto values = rbr::settings("size"_kw = 75ULL, "transparent"_fl);
 
  std::cout << rbr::fetch ( "transparent"_fl, values)                                 << "\n";
  std::cout << rbr::fetch ( "size"_kw, "size"_kw = 75ULL, "transparent"_fl)           << "\n";
  std::cout << rbr::fetch ( "value"_kw | 13.37, "size"_kw = 75ULL, "transparent"_fl)  << "\n";
  std::cout << rbr::fetch ( "modal"_fl | rbr::call([&]() { return i++; })
                          , "size"_kw = 75ULL, "transparent"_fl
                          )   << "\n\n";
 
  std::cout << "i = " << i << "\n";
}