locate()

template<typename Pred, concepts::product_type Tuple>

auto kumi::locate ( Tuple && t, Pred p )

inlinenodiscardconstexprnoexcept

Return the index of a value which type satisfies a given predicate.

Parameters

t	Tuple to process
p	Unary predicate. p must return a value convertible to bool for every element of t.

Returns

Integral index of the element inside the tuple if present, kumi::size<tuple<T...>>::value otherwise.

Examples:

#include <kumi/kumi.hpp>
#include <iostream>
#include <type_traits>
 
int main()
{
  auto t = kumi::tuple{1, 2., 0ULL, 3.f, 'z'};
 
  std::cout << std::boolalpha
            << kumi::locate( t, kumi::predicate<std::is_floating_point>() ) << "\n";
 
  std::cout << std::boolalpha << kumi::locate( t, [](auto e) { return e > 3; } ) << "\n";
}

#include <kumi/kumi.hpp>
#include <iostream>
#include <type_traits>
 
int main()
{
  using namespace kumi::literals;
  auto r = kumi::record{"a"_id = 1, "b"_id = 2., "c"_id = 0ULL, "d"_id = 3.f, "e"_id = 'z'};
 
  std::cout << std::boolalpha
            << kumi::locate( r, kumi::predicate<std::is_floating_point>() ) << "\n";
 
  std::cout << std::boolalpha << kumi::locate( r, [](auto e) { return e > 3; } ) << "\n";
}