locate()

template<typename Pred, concepts::product_type T>

auto kumi::locate ( T && t, Pred p )

inlinenodiscardconstexprnoexcept

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

On record types, this function operates as if the elements are ordered. The considered order is the order of declaration.

Parameters

t	Product Type 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 t if present, kumi::size<T>::value otherwise.

Examples:

Tuple:

#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";
}

Record:

#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";
}