C++ - får fel som jag inte förstår

g++ -std=c++20 -Wall -o obj/functions.o -c src/functions.cpp
g++ -std=c++20 -Wall -o obj/main.o -c src/main.cpp
In file included from /usr/include/c++/11/bits/stl_algobase.h:71,
                 from /usr/include/c++/11/bits/char_traits.h:39,
                 from /usr/include/c++/11/ios:40,
                 from /usr/include/c++/11/ostream:38,
                 from /usr/include/c++/11/iostream:39,
                 from src/main.cpp:1:
/usr/include/c++/11/bits/predefined_ops.h: In instantiation of ‘constexpr bool __gnu_cxx::__ops::_Iter_equals_val<_Value>::operator()(_Iterator) [with _Iterator = int*; _Value = const std::__cxx11::basic_string<char>]’:
/usr/include/c++/11/bits/stl_algobase.h:2069:14:   required from ‘constexpr _RandomAccessIterator std::__find_if(_RandomAccessIterator, _RandomAccessIterator, _Predicate, std::random_access_iterator_tag) [with _RandomAccessIterator = int*; _Predicate = __gnu_cxx::__ops::_Iter_equals_val<const std::__cxx11::basic_string<char> >]’
/usr/include/c++/11/bits/stl_algobase.h:2114:23:   required from here
src/main.cpp:59:22:   in ‘constexpr’ expansion of ‘std::find<int*, std::__cxx11::basic_string<char> >(std::begin<int, 3>(valid_modes), std::end<int, 3>(valid_modes), choice)’
/usr/include/c++/11/bits/stl_algo.h:3884:28:   in ‘constexpr’ expansion of ‘std::__find_if<int*, __gnu_cxx::__ops::_Iter_equals_val<const std::__cxx11::basic_string<char> > >(__first, __last, __gnu_cxx::__ops::__iter_equals_val<const std::__cxx11::basic_string<char> >((* & __val)))’
/usr/include/c++/11/bits/predefined_ops.h:270:24: error: no match for ‘operator==’ (operand types are ‘int’ and ‘const std::__cxx11::basic_string<char>’)
  270 |         { return *__it == _M_value; }
      |                  ~~~~~~^~~~~~~~~~~
In file included from /usr/include/c++/11/bits/stl_algobase.h:67,
                 from /usr/include/c++/11/bits/char_traits.h:39,
                 from /usr/include/c++/11/ios:40,
                 from /usr/include/c++/11/ostream:38,
                 from /usr/include/c++/11/iostream:39,
                 from src/main.cpp:1:
/usr/include/c++/11/bits/stl_iterator.h:1105:5: note: candidate: ‘template<class _IteratorL, class _IteratorR, class _Container>  requires requires(_IteratorL __lhs, _IteratorR __rhs) {{__lhs == __rhs} -> decltype(auto) [requires std::convertible_to<<placeholder>, bool>];} constexpr bool __gnu_cxx::operator==(const __gnu_cxx::__normal_iterator<_IteratorL, _Container>&, const __gnu_cxx::__normal_iterator<_IteratorR, _Container>&)’ (reversed)
 1105 |     operator==(const __normal_iterator<_IteratorL, _Container>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/11/bits/stl_iterator.h:1105:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/11/bits/stl_algobase.h:71,
                 from /usr/include/c++/11/bits/char_traits.h:39,
                 from /usr/include/c++/11/ios:40,
                 from /usr/include/c++/11/ostream:38,
                 from /usr/include/c++/11/iostream:39,
                 from src/main.cpp:1:
/usr/include/c++/11/bits/predefined_ops.h:270:24: note:   ‘const std::__cxx11::basic_string<char>’ is not derived from ‘const __gnu_cxx::__normal_iterator<_IteratorL, _Container>’
  270 |         { return *__it == _M_value; }
      |                  ~~~~~~^~~~~~~~~~~
In file included from /usr/include/x86_64-linux-gnu/c++/11/bits/c++allocator.h:33,
                 from /usr/include/c++/11/bits/allocator.h:46,
                 from /usr/include/c++/11/string:41,
                 from /usr/include/c++/11/bits/locale_classes.h:40,
                 from /usr/include/c++/11/bits/ios_base.h:41,
                 from /usr/include/c++/11/ios:42,
                 from /usr/include/c++/11/ostream:38,
                 from /usr/include/c++/11/iostream:39,
                 from src/main.cpp:1:
/usr/include/c++/11/ext/new_allocator.h:183:9: note: candidate: ‘template<class _Up> constexpr bool __gnu_cxx::operator==(const __gnu_cxx::new_allocator<char>&, const __gnu_cxx::new_allocator<_Tp>&)’ (reversed)
  183 |         operator==(const new_allocator&, const new_allocator<_Up>&)
      |         ^~~~~~~~
/usr/include/c++/11/ext/new_allocator.h:183:9: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/11/bits/stl_algobase.h:71,
                 from /usr/include/c++/11/bits/char_traits.h:39,
                 from /usr/include/c++/11/ios:40,
                 from /usr/include/c++/11/ostream:38,
                 from /usr/include/c++/11/iostream:39,
                 from src/main.cpp:1:
/usr/include/c++/11/bits/predefined_ops.h:270:24: note:   mismatched types ‘const __gnu_cxx::new_allocator<_Tp>’ and ‘int’
  270 |         { return *__it == _M_value; }
      |                  ~~~~~~^~~~~~~~~~~
In file included from /usr/include/c++/11/bits/stl_algobase.h:67,
                 from /usr/include/c++/11/bits/char_traits.h:39,
                 from /usr/include/c++/11/ios:40,
                 from /usr/include/c++/11/ostream:38,
                 from /usr/include/c++/11/iostream:39,
                 from src/main.cpp:1:
/usr/include/c++/11/bits/stl_iterator.h:494:5: note: candidate: ‘template<class _IteratorL, class _IteratorR> constexpr bool std::operator==(const std::reverse_iterator<_IteratorL>&, const std::reverse_iterator<_IteratorR>&) requires requires{{std::operator==::__x->base() == std::operator==::__y->base()} -> decltype(auto) [requires std::convertible_to<<placeholder>, bool>];}’ (reversed)
  494 |     operator==(const reverse_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/11/bits/stl_iterator.h:494:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/11/bits/stl_algobase.h:71,
                 from /usr/include/c++/11/bits/char_traits.h:39,
                 from /usr/include/c++/11/ios:40,
                 from /usr/include/c++/11/ostream:38,
                 from /usr/include/c++/11/iostream:39,
                 from src/main.cpp:1:
/usr/include/c++/11/bits/predefined_ops.h:270:24: note:   ‘const std::__cxx11::basic_string<char>’ is not derived from ‘const std::reverse_iterator<_IteratorL>’
  270 |         { return *__it == _M_value; }
      |                  ~~~~~~^~~~~~~~~~~
In file included from /usr/include/c++/11/bits/stl_algobase.h:67,
                 from /usr/include/c++/11/bits/char_traits.h:39,
                 from /usr/include/c++/11/ios:40,
                 from /usr/include/c++/11/ostream:38,
                 from /usr/include/c++/11/iostream:39,
                 from src/main.cpp:1:
/usr/include/c++/11/bits/stl_iterator.h:1533:5: note: candidate: ‘template<class _IteratorL, class _IteratorR> constexpr bool std::operator==(const std::move_iterator<_IteratorL>&, const std::move_iterator<_IteratorR>&) requires requires{{std::operator==::__x->base() == std::operator==::__y->base()} -> decltype(auto) [requires std::convertible_to<<placeholder>, bool>];}’ (reversed)
 1533 |     operator==(const move_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/11/bits/stl_iterator.h:1533:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/11/bits/stl_algobase.h:71,
                 from /usr/include/c++/11/bits/char_traits.h:39,
                 from /usr/include/c++/11/ios:40,
                 from /usr/include/c++/11/ostream:38,
                 from /usr/include/c++/11/iostream:39,
                 from src/main.cpp:1:
/usr/include/c++/11/bits/predefined_ops.h:270:24: note:   ‘const std::__cxx11::basic_string<char>’ is not derived from ‘const std::move_iterator<_IteratorL>’
  270 |         { return *__it == _M_value; }
      |                  ~~~~~~^~~~~~~~~~~
In file included from /usr/include/c++/11/string:41,
                 from /usr/include/c++/11/bits/locale_classes.h:40,
                 from /usr/include/c++/11/bits/ios_base.h:41,
                 from /usr/include/c++/11/ios:42,
                 from /usr/include/c++/11/ostream:38,
                 from /usr/include/c++/11/iostream:39,
                 from src/main.cpp:1:
/usr/include/c++/11/bits/allocator.h:218:5: note: candidate: ‘template<class _T1, class _T2> constexpr bool std::operator==(const std::allocator<_CharT>&, const std::allocator<_T2>&)’ (reversed)
  218 |     operator==(const allocator<_T1>&, const allocator<_T2>&)
      |     ^~~~~~~~
/usr/include/c++/11/bits/allocator.h:218:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/11/bits/stl_algobase.h:71,
                 from /usr/include/c++/11/bits/char_traits.h:39,
                 from /usr/include/c++/11/ios:40,
                 from /usr/include/c++/11/ostream:38,
                 from /usr/include/c++/11/iostream:39,
                 from src/main.cpp:1:
/usr/include/c++/11/bits/predefined_ops.h:270:24: note:   ‘const std::__cxx11::basic_string<char>’ is not derived from ‘const std::allocator<_CharT>’
  270 |         { return *__it == _M_value; }
      |                  ~~~~~~^~~~~~~~~~~
In file included from /usr/include/c++/11/bits/basic_string.h:48,
                 from /usr/include/c++/11/string:55,
                 from /usr/include/c++/11/bits/locale_classes.h:40,
                 from /usr/include/c++/11/bits/ios_base.h:41,
                 from /usr/include/c++/11/ios:42,
                 from /usr/include/c++/11/ostream:38,
                 from /usr/include/c++/11/iostream:39,
                 from src/main.cpp:1:
/usr/include/c++/11/string_view:541:5: note: candidate: ‘template<class _CharT, class _Traits> constexpr bool std::operator==(std::basic_string_view<_CharT, _Traits>, std::__type_identity_t<std::basic_string_view<_CharT, _Traits> >)’ (reversed)
  541 |     operator==(basic_string_view<_CharT, _Traits> __x,
      |     ^~~~~~~~
/usr/include/c++/11/string_view:541:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/11/bits/stl_algobase.h:71,
                 from /usr/include/c++/11/bits/char_traits.h:39,
                 from /usr/include/c++/11/ios:40,
                 from /usr/include/c++/11/ostream:38,
                 from /usr/include/c++/11/iostream:39,
                 from src/main.cpp:1:
/usr/include/c++/11/bits/predefined_ops.h:270:24: note:   ‘std::__cxx11::basic_string<char>’ is not derived from ‘std::basic_string_view<_CharT, _Traits>’
  270 |         { return *__it == _M_value; }
      |                  ~~~~~~^~~~~~~~~~~
In file included from /usr/include/c++/11/string:55,
                 from /usr/include/c++/11/bits/locale_classes.h:40,
                 from /usr/include/c++/11/bits/ios_base.h:41,
                 from /usr/include/c++/11/ios:42,
                 from /usr/include/c++/11/ostream:38,
                 from /usr/include/c++/11/iostream:39,
                 from src/main.cpp:1:
/usr/include/c++/11/bits/basic_string.h:6248:5: note: candidate: ‘template<class _CharT, class _Traits, class _Alloc> bool std::operator==(const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>&, const _CharT*)’ (reversed)
 6248 |     operator==(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/11/bits/basic_string.h:6248:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/11/bits/stl_algobase.h:71,
                 from /usr/include/c++/11/bits/char_traits.h:39,
                 from /usr/include/c++/11/ios:40,
                 from /usr/include/c++/11/ostream:38,
                 from /usr/include/c++/11/iostream:39,
                 from src/main.cpp:1:
/usr/include/c++/11/bits/predefined_ops.h:270:24: note:   mismatched types ‘const _CharT*’ and ‘int’
  270 |         { return *__it == _M_value; }
      |                  ~~~~~~^~~~~~~~~~~
In file included from /usr/include/c++/11/bits/std_thread.h:40,
                 from /usr/include/c++/11/stop_token:35,
                 from /usr/include/c++/11/thread:40,
                 from src/main.cpp:5:
/usr/include/c++/11/tuple:1528:5: note: candidate: ‘template<class ... _TElements, class ... _UElements> constexpr bool std::operator==(const std::tuple<_Tps ...>&, const std::tuple<_UTypes ...>&)’ (reversed)
 1528 |     operator==(const tuple<_TElements...>& __t,
      |     ^~~~~~~~
/usr/include/c++/11/tuple:1528:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/11/bits/stl_algobase.h:71,
                 from /usr/include/c++/11/bits/char_traits.h:39,
                 from /usr/include/c++/11/ios:40,
                 from /usr/include/c++/11/ostream:38,
                 from /usr/include/c++/11/iostream:39,
                 from src/main.cpp:1:
/usr/include/c++/11/bits/predefined_ops.h:270:24: note:   ‘const std::__cxx11::basic_string<char>’ is not derived from ‘const std::tuple<_Tps ...>’
  270 |         { return *__it == _M_value; }
      |                  ~~~~~~^~~~~~~~~~~
In file included from /usr/include/c++/11/bits/std_thread.h:44,
                 from /usr/include/c++/11/stop_token:35,
                 from /usr/include/c++/11/thread:40,
                 from src/main.cpp:5:
/usr/include/c++/11/bits/unique_ptr.h:753:5: note: candidate: ‘template<class _Tp, class _Dp, class _Up, class _Ep> bool std::operator==(const std::unique_ptr<_Tp, _Dp>&, const std::unique_ptr<_Up, _Ep>&)’ (reversed)
  753 |     operator==(const unique_ptr<_Tp, _Dp>& __x,
      |     ^~~~~~~~
/usr/include/c++/11/bits/unique_ptr.h:753:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/11/bits/stl_algobase.h:71,
                 from /usr/include/c++/11/bits/char_traits.h:39,
                 from /usr/include/c++/11/ios:40,
                 from /usr/include/c++/11/ostream:38,
                 from /usr/include/c++/11/iostream:39,
                 from src/main.cpp:1:
/usr/include/c++/11/bits/predefined_ops.h:270:24: note:   ‘const std::__cxx11::basic_string<char>’ is not derived from ‘const std::unique_ptr<_Tp, _Dp>’
  270 |         { return *__it == _M_value; }
      |                  ~~~~~~^~~~~~~~~~~
In file included from /usr/include/c++/11/bits/std_thread.h:44,
                 from /usr/include/c++/11/stop_token:35,
                 from /usr/include/c++/11/thread:40,
                 from src/main.cpp:5:
/usr/include/c++/11/bits/unique_ptr.h:760:5: note: candidate: ‘template<class _Tp, class _Dp> bool std::operator==(const std::unique_ptr<_Tp, _Dp>&, std::nullptr_t)’ (reversed)
  760 |     operator==(const unique_ptr<_Tp, _Dp>& __x, nullptr_t) noexcept
      |     ^~~~~~~~
/usr/include/c++/11/bits/unique_ptr.h:760:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/11/bits/stl_algobase.h:71,
                 from /usr/include/c++/11/bits/char_traits.h:39,
                 from /usr/include/c++/11/ios:40,
                 from /usr/include/c++/11/ostream:38,
                 from /usr/include/c++/11/iostream:39,
                 from src/main.cpp:1:
/usr/include/c++/11/bits/predefined_ops.h:270:24: note:   ‘const std::__cxx11::basic_string<char>’ is not derived from ‘const std::unique_ptr<_Tp, _Dp>’
  270 |         { return *__it == _M_value; }
      |                  ~~~~~~^~~~~~~~~~~
In file included from /usr/include/c++/11/bits/ios_base.h:46,
                 from /usr/include/c++/11/ios:42,
                 from /usr/include/c++/11/ostream:38,
                 from /usr/include/c++/11/iostream:39,
                 from src/main.cpp:1:
/usr/include/c++/11/system_error:368:3: note: candidate: ‘bool std::operator==(const std::error_code&, const std::error_condition&)’ (reversed)
  368 |   operator==(const error_code& __lhs, const error_condition& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/11/system_error:368:32: note:   no known conversion for argument 1 from ‘const std::__cxx11::basic_string<char>’ to ‘const std::error_code&’
  368 |   operator==(const error_code& __lhs, const error_condition& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~^~~~~
In file included from /usr/include/c++/11/iosfwd:40,
                 from /usr/include/c++/11/ios:38,
                 from /usr/include/c++/11/ostream:38,
                 from /usr/include/c++/11/iostream:39,
                 from src/main.cpp:1:
/usr/include/c++/11/bits/postypes.h:222:5: note: candidate: ‘template<class _StateT> bool std::operator==(const std::fpos<_StateT>&, const std::fpos<_StateT>&)’
  222 |     operator==(const fpos<_StateT>& __lhs, const fpos<_StateT>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/11/bits/postypes.h:222:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/11/bits/stl_algobase.h:71,
                 from /usr/include/c++/11/bits/char_traits.h:39,
                 from /usr/include/c++/11/ios:40,
                 from /usr/include/c++/11/ostream:38,
                 from /usr/include/c++/11/iostream:39,
                 from src/main.cpp:1:
/usr/include/c++/11/bits/predefined_ops.h:270:24: note:   mismatched types ‘const std::fpos<_StateT>’ and ‘int’
  270 |         { return *__it == _M_value; }
      |                  ~~~~~~^~~~~~~~~~~
In file included from /usr/include/c++/11/bits/stl_algobase.h:64,
                 from /usr/include/c++/11/bits/char_traits.h:39,
                 from /usr/include/c++/11/ios:40,
                 from /usr/include/c++/11/ostream:38,
                 from /usr/include/c++/11/iostream:39,
                 from src/main.cpp:1:
/usr/include/c++/11/bits/stl_pair.h:466:5: note: candidate: ‘template<class _T1, class _T2> constexpr bool std::operator==(const std::pair<_T1, _T2>&, const std::pair<_T1, _T2>&)’
  466 |     operator==(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
      |     ^~~~~~~~
/usr/include/c++/11/bits/stl_pair.h:466:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/11/bits/stl_algobase.h:71,
                 from /usr/include/c++/11/bits/char_traits.h:39,
                 from /usr/include/c++/11/ios:40,
                 from /usr/include/c++/11/ostream:38,
                 from /usr/include/c++/11/iostream:39,
                 from src/main.cpp:1:
/usr/include/c++/11/bits/predefined_ops.h:270:24: note:   mismatched types ‘const std::pair<_T1, _T2>’ and ‘int’
  270 |         { return *__it == _M_value; }
      |                  ~~~~~~^~~~~~~~~~~
In file included from /usr/include/c++/11/bits/basic_string.h:48,
                 from /usr/include/c++/11/string:55,
                 from /usr/include/c++/11/bits/locale_classes.h:40,
                 from /usr/include/c++/11/bits/ios_base.h:41,
                 from /usr/include/c++/11/ios:42,
                 from /usr/include/c++/11/ostream:38,
                 from /usr/include/c++/11/iostream:39,
                 from src/main.cpp:1:
/usr/include/c++/11/string_view:535:5: note: candidate: ‘template<class _CharT, class _Traits> constexpr bool std::operator==(std::basic_string_view<_CharT, _Traits>, std::basic_string_view<_CharT, _Traits>)’
  535 |     operator==(basic_string_view<_CharT, _Traits> __x,
      |     ^~~~~~~~
/usr/include/c++/11/string_view:535:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/11/bits/stl_algobase.h:71,
                 from /usr/include/c++/11/bits/char_traits.h:39,
                 from /usr/include/c++/11/ios:40,
                 from /usr/include/c++/11/ostream:38,
                 from /usr/include/c++/11/iostream:39,
                 from src/main.cpp:1:
/usr/include/c++/11/bits/predefined_ops.h:270:24: note:   mismatched types ‘std::basic_string_view<_CharT, _Traits>’ and ‘int’
  270 |         { return *__it == _M_value; }
      |                  ~~~~~~^~~~~~~~~~~
In file included from /usr/include/c++/11/string:55,
                 from /usr/include/c++/11/bits/locale_classes.h:40,
                 from /usr/include/c++/11/bits/ios_base.h:41,
                 from /usr/include/c++/11/ios:42,
                 from /usr/include/c++/11/ostream:38,
                 from /usr/include/c++/11/iostream:39,
                 from src/main.cpp:1:
/usr/include/c++/11/bits/basic_string.h:6226:5: note: candidate: ‘template<class _CharT, class _Traits, class _Alloc> bool std::operator==(const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>&, const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>&)’
 6226 |     operator==(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/11/bits/basic_string.h:6226:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/11/bits/stl_algobase.h:71,
                 from /usr/include/c++/11/bits/char_traits.h:39,
                 from /usr/include/c++/11/ios:40,
                 from /usr/include/c++/11/ostream:38,
                 from /usr/include/c++/11/iostream:39,
                 from src/main.cpp:1:
/usr/include/c++/11/bits/predefined_ops.h:270:24: note:   mismatched types ‘const std::__cxx11::basic_string<_CharT, _Traits, _Allocator>’ and ‘int’
  270 |         { return *__it == _M_value; }
      |                  ~~~~~~^~~~~~~~~~~
In file included from /usr/include/c++/11/string:55,
                 from /usr/include/c++/11/bits/locale_classes.h:40,
                 from /usr/include/c++/11/bits/ios_base.h:41,
                 from /usr/include/c++/11/ios:42,
                 from /usr/include/c++/11/ostream:38,
                 from /usr/include/c++/11/iostream:39,
                 from src/main.cpp:1:
/usr/include/c++/11/bits/basic_string.h:6234:5: note: candidate: ‘template<class _CharT> typename __gnu_cxx::__enable_if<std::__is_char<_Tp>::__value, bool>::__type std::operator==(const std::__cxx11::basic_string<_CharT>&, const std::__cxx11::basic_string<_CharT>&)’
 6234 |     operator==(const basic_string<_CharT>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/11/bits/basic_string.h:6234:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/11/bits/stl_algobase.h:71,
                 from /usr/include/c++/11/bits/char_traits.h:39,
                 from /usr/include/c++/11/ios:40,
                 from /usr/include/c++/11/ostream:38,
                 from /usr/include/c++/11/iostream:39,
                 from src/main.cpp:1:
/usr/include/c++/11/bits/predefined_ops.h:270:24: note:   mismatched types ‘const std::__cxx11::basic_string<_CharT>’ and ‘int’
  270 |         { return *__it == _M_value; }
      |                  ~~~~~~^~~~~~~~~~~
In file included from /usr/include/c++/11/bits/locale_facets.h:48,
                 from /usr/include/c++/11/bits/basic_ios.h:37,
                 from /usr/include/c++/11/ios:44,
                 from /usr/include/c++/11/ostream:38,
                 from /usr/include/c++/11/iostream:39,
                 from src/main.cpp:1:
/usr/include/c++/11/bits/streambuf_iterator.h:226:5: note: candidate: ‘template<class _CharT, class _Traits> bool std::operator==(const std::istreambuf_iterator<_CharT, _Traits>&, const std::istreambuf_iterator<_CharT, _Traits>&)’
  226 |     operator==(const istreambuf_iterator<_CharT, _Traits>& __a,
      |     ^~~~~~~~
/usr/include/c++/11/bits/streambuf_iterator.h:226:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/11/bits/stl_algobase.h:71,
                 from /usr/include/c++/11/bits/char_traits.h:39,
                 from /usr/include/c++/11/ios:40,
                 from /usr/include/c++/11/ostream:38,
                 from /usr/include/c++/11/iostream:39,
                 from src/main.cpp:1:
/usr/include/c++/11/bits/predefined_ops.h:270:24: note:   mismatched types ‘const std::istreambuf_iterator<_CharT, _Traits>’ and ‘int’
  270 |         { return *__it == _M_value; }
      |                  ~~~~~~^~~~~~~~~~~
In file included from /usr/include/c++/11/tuple:39,
                 from /usr/include/c++/11/bits/std_thread.h:40,
                 from /usr/include/c++/11/stop_token:35,
                 from /usr/include/c++/11/thread:40,
                 from src/main.cpp:5:
/usr/include/c++/11/array:276:5: note: candidate: ‘template<class _Tp, long unsigned int _Nm> constexpr bool std::operator==(const std::array<_Tp, _Nm>&, const std::array<_Tp, _Nm>&)’
  276 |     operator==(const array<_Tp, _Nm>& __one, const array<_Tp, _Nm>& __two)
      |     ^~~~~~~~
/usr/include/c++/11/array:276:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/11/bits/stl_algobase.h:71,
                 from /usr/include/c++/11/bits/char_traits.h:39,
                 from /usr/include/c++/11/ios:40,
                 from /usr/include/c++/11/ostream:38,
                 from /usr/include/c++/11/iostream:39,
                 from src/main.cpp:1:
/usr/include/c++/11/bits/predefined_ops.h:270:24: note:   mismatched types ‘const std::array<_Tp, _Nm>’ and ‘int’
  270 |         { return *__it == _M_value; }
      |                  ~~~~~~^~~~~~~~~~~
In file included from /usr/include/c++/11/vector:67,
                 from src/main.cpp:7:
/usr/include/c++/11/bits/stl_vector.h:1892:5: note: candidate: ‘template<class _Tp, class _Alloc> bool std::operator==(const std::vector<_Tp, _Alloc>&, const std::vector<_Tp, _Alloc>&)’
 1892 |     operator==(const vector<_Tp, _Alloc>& __x, const vector<_Tp, _Alloc>& __y)
      |     ^~~~~~~~
/usr/include/c++/11/bits/stl_vector.h:1892:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/11/bits/stl_algobase.h:71,
                 from /usr/include/c++/11/bits/char_traits.h:39,
                 from /usr/include/c++/11/ios:40,
                 from /usr/include/c++/11/ostream:38,
                 from /usr/include/c++/11/iostream:39,
                 from src/main.cpp:1:
/usr/include/c++/11/bits/predefined_ops.h:270:24: note:   mismatched types ‘const std::vector<_Tp, _Alloc>’ and ‘int’
  270 |         { return *__it == _M_value; }
      |                  ~~~~~~^~~~~~~~~~~
In file included from /usr/include/c++/11/string:41,
                 from /usr/include/c++/11/bits/locale_classes.h:40,
                 from /usr/include/c++/11/bits/ios_base.h:41,
                 from /usr/include/c++/11/ios:42,
                 from /usr/include/c++/11/ostream:38,
                 from /usr/include/c++/11/iostream:39,
                 from src/main.cpp:1:
/usr/include/c++/11/bits/allocator.h:204:7: note: candidate: ‘constexpr bool std::operator==(const std::allocator<char>&, const std::allocator<char>&)’
  204 |       operator==(const allocator&, const allocator&) _GLIBCXX_NOTHROW
      |       ^~~~~~~~
/usr/include/c++/11/bits/allocator.h:204:18: note:   no known conversion for argument 1 from ‘int’ to ‘const std::allocator<char>&’
  204 |       operator==(const allocator&, const allocator&) _GLIBCXX_NOTHROW
      |                  ^~~~~~~~~~~~~~~~
In file included from /usr/include/c++/11/bits/ios_base.h:46,
                 from /usr/include/c++/11/ios:42,
                 from /usr/include/c++/11/ostream:38,
                 from /usr/include/c++/11/iostream:39,
                 from src/main.cpp:1:
/usr/include/c++/11/system_error:362:3: note: candidate: ‘bool std::operator==(const std::error_code&, const std::error_code&)’
  362 |   operator==(const error_code& __lhs, const error_code& __rhs) noexcept
      |   ^~~~~~~~
/usr/include/c++/11/system_error:362:32: note:   no known conversion for argument 1 from ‘int’ to ‘const std::error_code&’
  362 |   operator==(const error_code& __lhs, const error_code& __rhs) noexcept
      |              ~~~~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/11/system_error:376:3: note: candidate: ‘bool std::operator==(const std::error_condition&, const std::error_condition&)’
  376 |   operator==(const error_condition& __lhs,
      |   ^~~~~~~~
/usr/include/c++/11/system_error:376:37: note:   no known conversion for argument 1 from ‘int’ to ‘const std::error_condition&’
  376 |   operator==(const error_condition& __lhs,
      |              ~~~~~~~~~~~~~~~~~~~~~~~^~~~~
In file included from /usr/include/c++/11/stop_token:35,
                 from /usr/include/c++/11/thread:40,
                 from src/main.cpp:5:
/usr/include/c++/11/bits/std_thread.h:281:3: note: candidate: ‘bool std::operator==(std::thread::id, std::thread::id)’
  281 |   operator==(thread::id __x, thread::id __y) noexcept
      |   ^~~~~~~~
/usr/include/c++/11/bits/std_thread.h:281:25: note:   no known conversion for argument 1 from ‘int’ to ‘std::thread::id’
  281 |   operator==(thread::id __x, thread::id __y) noexcept
      |              ~~~~~~~~~~~^~~
make: *** [Makefile:47: obj/main.o] Error 1

#include <iostream>
#include <chrono>
#include <string>
#include <cstdlib>
#include <thread>
#include <cmath>
#include <vector>
#include <numeric>
#include <atomic>
#include "include/functions.h"

void primes_in_range(uint64_t lower_limit, uint64_t upper_limit);

std::atomic<unsigned int> prime_count = 0;

int main() {
    using namespace std::chrono_literals;
    int thread_count = std::thread::hardware_concurrency();
    switch (thread_count) {
        case 0:
            std::cout << "Implementation does not seem to support 'std::thread::hardware_concurrency()'." << '\n';
            std::exit(EXIT_FAILURE);
        case 1:
            std::cout << "System only suppports a single thread." << '\n';
            break;
        default:
            std::cout << "System supports " << thread_count << " threads." << '\n';
            break;
    }
    constexpr int repeat_val = 10;
    uint64_t iteration_length_arr[repeat_val];
    long double avg_search_time = 0.0;
    constexpr uint64_t lower_search_limit = 1;
    constexpr uint64_t upper_search_limit = 100000000;
    int remainder_range_start = 0;
    int remainder_range_end = 0;
    uint64_t start_of_range[thread_count] = {};
    uint64_t end_of_range[thread_count] = {};
    std::string choice;
    std::string yes_choices[] = {"Y", "y", "Yes", "yes"};
    std::string no_choices[] = {"N", "n", "No", "no"};
    int valid_modes[] = {0, 1, 2};
    int mode_select = 0;

    std::chrono::_V2::steady_clock::time_point prog_start_time;
    std::chrono::_V2::steady_clock::time_point prog_stop_time;
    uint64_t prog_runtime_nanoseconds = 0;
    std::chrono::duration<uint64_t, std::nano> elapsed_prog_runtime;

    ldiv_t result;
    
    while (true) {
        std::cout << "Select benchmark mode from list below:" << '\n';
        std::cout << "0. Single-threaded benchmark." << '\n';
        std::cout << "1. Multi-threaded benchmark (" << thread_count << " threads)." << '\n';
        std::cout << "2. Exit program." << '\n';
        std::cout << "Enter one of the listed values: ";
        std::cin >> mode_select;
        if (std::find(std::begin(valid_modes), std::end(valid_modes), choice) != std::end(valid_modes)) {
            break;
        } else {
            std::cout << "Invalid mode select, try again!" << '\n';
        }
    }

    switch (mode_select) {
        case 0:
            //Singlethreaded.
            std::cout << "Starting singlethreaded benchmark..." << '\n';
            prog_start_time = std::chrono::steady_clock::now();

            for (int k = 0; k < repeat_val; k++) {
                std::cout << "Iteration " << (k + 1) << " of " << repeat_val << " Runtime (ns): ";
                auto iteration_start_time = std::chrono::steady_clock::now();

                primes_in_range(lower_search_limit, upper_search_limit);

                auto iteration_stop_time = std::chrono::steady_clock::now();
                std::chrono::duration<uint64_t, std::nano> elapsed_single_iteration = iteration_stop_time - iteration_start_time; //how many nanoseconds have elapsed.
                iteration_length_arr[k] = elapsed_single_iteration.count(); //store elapsed_single_iteration nanoseconds in iteration_length_arr.
                std::cout << elapsed_single_iteration.count() << '\n';
            }

            avg_search_time = std::accumulate(std::begin(iteration_length_arr), std::end(iteration_length_arr), avg_search_time) / repeat_val;

            prog_stop_time = std::chrono::steady_clock::now();
            elapsed_prog_runtime = prog_stop_time - prog_start_time; //how many nanoseconds have elapsed.
            prog_runtime_nanoseconds = elapsed_prog_runtime.count();

            std::cout << "Prime singlethreaded benchmark is done!" << '\n';

            std::cout << "\n**** Results ****" << '\n';
            std::cout << "Program ran for total of (DD:HH:MM:SS.SSSSSSSSS): " << func::to_days_hours_minutes_seconds(prog_runtime_nanoseconds) << '\n';
            std::cout << "\n";
            std::cout << "Program ran for: " << prog_runtime_nanoseconds << " ns" << '\n';
            std::cout << "\n";
            std::cout << "Average time to find all primes between " << lower_search_limit << " and " << upper_search_limit << " was (DD:HH:MM:SS.SSSSSSSSS):" << '\n';
            std::cout << func::to_days_hours_minutes_seconds((uint64_t) avg_search_time) << '\n';
            std::cout << "\n";
            std::cout << "Average search time: " << (uint64_t) avg_search_time << " ns" << '\n';
            std::cout << "Number of primes found is: " << prime_count / repeat_val << '\n';

            break;
        case 1:
            //Multithreaded.
            result = std::div(upper_search_limit, (long) thread_count);
            std::cout << "Numerator: " << upper_search_limit << '\n';
            std::cout << "Denominator (also how many threads): " << thread_count << '\n';
            std::cout << "Quotient: " << result.quot << '\n';
            std::cout << "Remainder: " << result.rem << '\n';
            std::cout << "  ****  " << '\n';
    
            //Calculating start and end vales for the ranges.
            for (int i = 0; i < thread_count; i++) {
                if (i == 0) {
                    start_of_range[i] = lower_search_limit;
                    end_of_range[i] = result.quot;
                } else {
                    start_of_range[i] = end_of_range[i - 1] + 1;
                    end_of_range[i] = (start_of_range[i] - 1) + result.quot;
                }
            }
    
            //Calculating start and end values for remainder range.
            if (result.rem != 0) {
                remainder_range_start = (upper_search_limit - result.rem) + 1;
                remainder_range_end = upper_search_limit;
            }

            /* std::cout << "Start prime_threads between " << lower_search_limit << " and " << upper_search_limit << "? [Y/n]: ";
            std::cin >> choice;
            if (std::find(std::begin(yes_choices), std::end(yes_choices), choice) != std::end(yes_choices)) { */
            std::cout << "Starting multithreaded prime benchmark..." << '\n';
            prog_start_time = std::chrono::steady_clock::now();

            for (int k = 0; k < repeat_val; k++) {
                std::cout << "Iteration " << (k + 1) << " of " << repeat_val << " Runtime (ns): ";
                //Create vector to hold main thread objects.
                std::vector<std::thread> main_threads;

                auto iteration_start_time = std::chrono::steady_clock::now();
                //Create and start main threads.
                for (int i = 0; i < thread_count; i++) {
                    main_threads.push_back(std::thread(primes_in_range, start_of_range[i], end_of_range[i]));
                }

                //Join main threads.
                for (auto &th : main_threads) {
                    th.join();
                }

                //Create remainder thread (if needed).
                if (result.rem != 0) {
                    std::thread remainder_thread = std::thread(primes_in_range, remainder_range_start, remainder_range_end);
                        
                    remainder_thread.join();
                }

                auto iteration_stop_time = std::chrono::steady_clock::now();
                std::chrono::duration<uint64_t, std::nano> elapsed_single_iteration = iteration_stop_time - iteration_start_time; //how many nanoseconds have elapsed.
                iteration_length_arr[k] = elapsed_single_iteration.count(); //store elapsed_single_iteration nanoseconds in iteration_length_arr.
                std::cout << elapsed_single_iteration.count() << '\n';
            }

            avg_search_time = std::accumulate(std::begin(iteration_length_arr), std::end(iteration_length_arr), avg_search_time) / repeat_val;

            prog_stop_time = std::chrono::steady_clock::now();
            elapsed_prog_runtime = prog_stop_time - prog_start_time; //how many nanoseconds have elapsed.
            prog_runtime_nanoseconds = elapsed_prog_runtime.count();

            std::cout << "Prime multithreaded benchmark is done!" << '\n';

            std::cout << "\n**** Results ****" << '\n';
            std::cout << "Program ran for total of (DD:HH:MM:SS.SSSSSSSSS): " << func::to_days_hours_minutes_seconds(prog_runtime_nanoseconds) << '\n';
            std::cout << "\n";
            std::cout << "Program ran for: " << prog_runtime_nanoseconds << " ns" << '\n';
            std::cout << "\n";
            std::cout << "Average time to find all primes between " << lower_search_limit << " and " << upper_search_limit << " was (DD:HH:MM:SS.SSSSSSSSS):" << '\n';
            std::cout << func::to_days_hours_minutes_seconds((uint64_t) avg_search_time) << '\n';
            std::cout << "\n";
            std::cout << "Average search time: " << (uint64_t) avg_search_time << " ns" << '\n';
            std::cout << "Number of primes found is: " << prime_count / repeat_val << '\n';

            break;
        case 2:
            //Exit program.
            std::cout << "Exited program." << '\n';
            break;
        default:
            std::cout << "Defaulted to exiting program since no valid input was made." << '\n';
            std::exit(EXIT_FAILURE);
        }
    
    return 0;
}

void primes_in_range(uint64_t lower_limit, uint64_t upper_limit) {
    unsigned int count = 0;
    for (uint64_t i = lower_limit; i < upper_limit + 1; i++) {
        if (func::prime::is_prime(i)) {
            count++;
        }
    }

    prime_count += count;
}