python library can't handle bare Tuple<T,S> return type from Arduino Library about arduino-simple-rpc HOT 8 CLOSED

The internal structure of both Tuple and Object types are nested, e.g., Tuple<char, int, float> is shorthand for Tuple<char, Tuple<int, Tuple<float, Tuple<>>>>. If these types were merged, data in such a structure would be presented to the caller as an overly complicated nested structure, e.g., ('a', (10, (1.2))) instead of the expected ('a', 10, 1.2).

To circumvent this, we need two types of these objects, one that serialises to a flat list and one that has an explicit internal structure. To stick with the previous example, Object<char, int, float> is shorthand for Object<Tuple<char, Tuple<int, Tuple <float, Tuple <>>>> and data in such a structure is presented to the caller as a simple tuple, e.g., ('a', 10, 1.2).

So in a sense, the Object type places the parentheses around the values. This however means a bare Tuple no longer has a representation for the caller.

I will try to explain this in the documentation as well.

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I tried to explain it in this note.

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Yeah after playing with it more I see the concept and understand the idea. Indeed merging them makes little sense. Perhaps my confusion is purely based on semantics about what the flat type is called and what the nested type is called. In a sense I was thinking of Object as the flat one, perhaps due thinking about them like structs in C, and Tuple as the nested one.

Regardless this was my mistake and I agree on all points you have made. I obviously missed the note! Sorry for the noise. Feel free to close the Bug Report. As always thank you for the excellent library

P.S
As an aside, I personally prefer to use the STL, even on Arduino, so I have patched your C++ library to at least support std::string, but I could likely include support for std::vector and std::array (or others). Is that something you are interested in? If so I can open a feature request on the other repo and eventually put in a PR for them. I don't mind maintaining internal patches for the stuff we are working on but I only bring it up because support for Arduino String is there. I understand what we are doing is somewhat niche (power management for an RF system) so I don't want to overstep.

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You did not miss the note, I wrote it after you opened this issue.

I would have preferred using the STL as well, but to my knowledge it is not distributed by default with the Arduino cores. If this is the case, it may be a bit more difficult for an end user to use this library. Of course I could be wrong here.

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I just thought I could give it a go, but the standard installation does not seem to work, at least not in my setup. As soon as I include ArduinoSTL.h, I get the following errors.

.../libraries/ArduinoSTL/src/del_opvnt.cpp:25:58: error: 'nothrow_t' in namespace 'std' does not name a type
 _UCXXEXPORT void operator delete[](void* ptr, const std::nothrow_t& ) throw(){
                                                          ^~~~~~~~~
.../libraries/ArduinoSTL/src/del_ops.cpp:25:50: error: 'std::size_t' has not been declared
 _UCXXEXPORT void operator delete(void* ptr, std::size_t) throw(){
                                                  ^~~~~~
.../libraries/ArduinoSTL/src/del_opnt.cpp:25:56: error: 'nothrow_t' in namespace 'std' does not name a type
 _UCXXEXPORT void operator delete(void* ptr, const std::nothrow_t& ) throw() {
                                                        ^~~~~~~~~
.../libraries/ArduinoSTL/src/del_opvs.cpp:25:53: error: 'std::size_t' has not been declared
 _UCXXEXPORT void operator delete[](void * ptr, std::size_t) throw(){

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Mini rant to start: I honestly hate how Arduino pushes this weird C within C++ style of programming. I understand they are trying to be beginner friendly but I feel it creates a bunch of weird corner cases when you are trying to do something a little more involved. Mini rant over.

So honestly I have not used ArduinoSTL.h but those errors seemed strange. A quick Google search points to these threads: 1 and 2 which tl;dr suggest changing #include <ArduinoSTL.h> to #include "ArduinoSTL.h" or changing Arduino IDE version

All that said the way I use the STL is to include -lstdc++_nano in the build flags. For the Teensy line of boards I modify boards.txt > teensyXX.build.flags.libs to include the additional library. For Arduino it is somewhat more involved, requiring either arduino-cli or modifying other .txt. files (some info here). The nice thing about lstdc++_nano is it does not throw, is relatively light weight and imo fulfills the role of ArduinoSTL.h.

Of course modifying Arduino files is daunting for many users so I understand that any STL inclusion would cater to a niche of a niche.

(edit: made links visible)

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Changing the <> to "" did not help. I am also not sure whether this library is still maintained.

I mainly use arduino-cli for my projects and adding a build flag seems to be rather straightforward. Do you perhaps have an example project where std::string is used together with build options, include and library paths?

I would not mind adding some optional extra complexity. We could think about an additional include for STL support in conjunction with some build instructions.

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I opened discussion #24 for this topic.

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