conversion json to std::map doesn't work for types <int, double>

[TheWaveWarden]

//<int, double> doesn't work
std::map<int, double> map_input3 = {{1, 2.0}};
json json_map3(map_input3);
std::map<int, double> map_output3 = json_map3;

tested on Ubuntu18, compiler is g++, version 3.1.2

as previously discussed in
#600

[TheWaveWarden]

error message:

/opt/robodev/include/nlohmann/detail/conversions/from_json.hpp: In instantiation of ‘void nlohmann::detail::from_json(const BasicJsonType&, std::pair<_Tp1, _Tp2>&) [with BasicJsonType = nlohmann::basic_json<>; A1 = const int; A2 = double]’:
/opt/robodev/include/nlohmann/detail/conversions/from_json.hpp:288:25:   required from ‘decltype ((nlohmann::detail::from_json(j, val), void())) nlohmann::detail::from_json_fn::call(const BasicJsonType&, T&, nlohmann::detail::priority_tag<1>) const [with BasicJsonType = nlohmann::basic_json<>; T = std::pair<const int, double>; decltype ((nlohmann::detail::from_json(j, val), void())) = void]’
/opt/robodev/include/nlohmann/detail/conversions/from_json.hpp:309:47:   required from ‘void nlohmann::detail::from_json_fn::operator()(const BasicJsonType&, T&) const [with BasicJsonType = nlohmann::basic_json<>; T = std::pair<const int, double>]’
/opt/robodev/include/nlohmann/adl_serializer.hpp:26:30:   required from ‘static void nlohmann::adl_serializer< <template-parameter-1-1>, <template-parameter-1-2> >::from_json(BasicJsonType&&, ValueType&) [with BasicJsonType = const nlohmann::basic_json<>&; ValueType = std::pair<const int, double>; <template-parameter-1-1> = std::pair<const int, double>; <template-parameter-1-2> = void]’
/opt/robodev/include/nlohmann/json.hpp:2570:45:   required from ‘ValueType nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer>::get() const [with ValueTypeCV = std::pair<const int, double>; ValueType = std::pair<const int, double>; typename std::enable_if<(((! nlohmann::detail::is_basic_json<ValueType>::value) && nlohmann::detail::has_from_json<nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer>, ValueType>::value) && (! nlohmann::detail::has_non_default_from_json<nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer>, ValueType>::value)), int>::type <anonymous> = 0; ObjectType = std::map; ArrayType = std::vector; StringType = std::__cxx11::basic_string<char>; BooleanType = bool; NumberIntegerType = long int; NumberUnsignedType = long unsigned int; NumberFloatType = double; AllocatorType = std::allocator; JSONSerializer = nlohmann::adl_serializer]’
/opt/robodev/include/nlohmann/detail/conversions/from_json.hpp:150:5:   required from ‘nlohmann::detail::from_json_array_impl(const BasicJsonType&, CompatibleArrayType&, nlohmann::detail::priority_tag<0>)::<lambda(const BasicJsonType&)> [with BasicJsonType = nlohmann::basic_json<>; CompatibleArrayType = std::map<int, double>]’
/opt/robodev/include/nlohmann/detail/conversions/from_json.hpp:145:51:   [ skipping 3 instantiation contexts, use -ftemplate-backtrace-limit=0 to disable ]
/opt/robodev/include/nlohmann/detail/conversions/from_json.hpp:288:25:   required from ‘decltype ((nlohmann::detail::from_json(j, val), void())) nlohmann::detail::from_json_fn::call(const BasicJsonType&, T&, nlohmann::detail::priority_tag<1>) const [with BasicJsonType = nlohmann::basic_json<>; T = std::map<int, double>; decltype ((nlohmann::detail::from_json(j, val), void())) = void]’
/opt/robodev/include/nlohmann/detail/conversions/from_json.hpp:309:47:   required from ‘void nlohmann::detail::from_json_fn::operator()(const BasicJsonType&, T&) const [with BasicJsonType = nlohmann::basic_json<>; T = std::map<int, double>]’
/opt/robodev/include/nlohmann/adl_serializer.hpp:26:30:   required from ‘static void nlohmann::adl_serializer< <template-parameter-1-1>, <template-parameter-1-2> >::from_json(BasicJsonType&&, ValueType&) [with BasicJsonType = const nlohmann::basic_json<>&; ValueType = std::map<int, double>; <template-parameter-1-1> = std::map<int, double>; <template-parameter-1-2> = void]’
/opt/robodev/include/nlohmann/json.hpp:2570:45:   required from ‘ValueType nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer>::get() const [with ValueTypeCV = std::map<int, double>; ValueType = std::map<int, double>; typename std::enable_if<(((! nlohmann::detail::is_basic_json<ValueType>::value) && nlohmann::detail::has_from_json<nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer>, ValueType>::value) && (! nlohmann::detail::has_non_default_from_json<nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer>, ValueType>::value)), int>::type <anonymous> = 0; ObjectType = std::map; ArrayType = std::vector; StringType = std::__cxx11::basic_string<char>; BooleanType = bool; NumberIntegerType = long int; NumberUnsignedType = long unsigned int; NumberFloatType = double; AllocatorType = std::allocator; JSONSerializer = nlohmann::adl_serializer]’
/opt/robodev/include/nlohmann/json.hpp:2832:30:   required from ‘nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer>::operator ValueType() const [with ValueType = std::map<int, double>; typename std::enable_if<(((((! std::is_pointer<_Ptr>::value) && (! std::is_same<ValueType, nlohmann::detail::json_ref<nlohmann::basic_json<ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer> > >::value)) && (! std::is_same<ValueType, typename StringType::value_type>::value)) && (! nlohmann::detail::is_basic_json<BasicJsonType>::value)) && (! std::is_same<ValueType, std::initializer_list<typename StringType::value_type> >::value)), int>::type <anonymous> = 0; ObjectType = std::map; ArrayType = std::vector; StringType = std::__cxx11::basic_string<char>; BooleanType = bool; NumberIntegerType = long int; NumberUnsignedType = long unsigned int; NumberFloatType = double; AllocatorType = std::allocator; JSONSerializer = nlohmann::adl_serializer]’
/home/frederik_siepe/rd_root/repos/rd_path_planning/src/rd/path_planner/rd_path_planner.cpp:58:38:   required from here
/opt/robodev/include/nlohmann/detail/conversions/from_json.hpp:265:7: error: use of deleted function ‘std::pair<_T1, _T2>& std::pair<_T1, _T2>::operator=(typename std::conditional<std::__not_<std::__and_<std::is_copy_assignable<_Tp>, std::is_copy_assignable<_T2> > >::value, const std::pair<_T1, _T2>&, const std::__nonesuch_no_braces&>::type) [with _T1 = const int; _T2 = double; typename std::conditional<std::__not_<std::__and_<std::is_copy_assignable<_Tp>, std::is_copy_assignable<_T2> > >::value, const std::pair<_T1, _T2>&, const std::__nonesuch_no_braces&>::type = const std::pair<const int, double>&]’
     p = {j.at(0).template get<A1>(), j.at(1).template get<A2>()};
     ~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/c++/7/bits/stl_algobase.h:64:0,
                 from /usr/include/c++/7/bits/char_traits.h:39,
                 from /usr/include/c++/7/ios:40,
                 from /usr/include/c++/7/istream:38,
                 from /usr/include/c++/7/sstream:38,
                 from /usr/include/c++/7/complex:45,
                 from /usr/include/eigen3/Eigen/Core:80,
                 from /opt/ros/melodic/include/eigen_conversions/eigen_kdl.h:37,
                 from /home/frederik_siepe/rd_root/repos/rd_path_planning/src/rd/path_planner/rd_path_planner.cpp:1:
/usr/include/c++/7/bits/stl_pair.h:378:7: note: declared here
       operator=(typename conditional<

[theodelrieu]

Your code works on my machine with GCC 8.2. Note that your compiler is not supported.

What version of the library are you using?

[TheWaveWarden]

I'm using json-version version 3.1.2, which seems not to be up to date as well.
Then the error is on my side, my apologies. I will try a newer version and/or supported compiler later and let you know if there are still complications!
Many Thanks!