Error in convertFromString<double>

[moritzknaust]

I found a strange error in the convertFromString method. If I use the behaviortree in a rqt-gui plugin, the conversion from string to double is wrong. For example "1.23" is converted to 1 instead of 1.23. This only happens if I use a rqt-gui plugin. When I use the behaviortree in a normal ROS node everything works fine.

I think this error is related to this topic: https://www.reddit.com/r/cpp/comments/2e68nd/stdstod_is_locale_dependant_but_the_docs_does_not/
Maybe Qt changes the used locale to another value, but I am not sure about this.

I have fixed it by using std::istringstream for the conversion instead of std::stod like it is explained in the post. My new version of convertFromString in basic_types.cpp is now the following:

template <>
double convertFromString<double>(StringView str)
{
    std::istringstream iss(str.data());
    iss.imbue(std::locale("C"));
    double temp;
    iss >> temp;
    return temp;
}

This error is very confusing and generates really unexpected behaviors, so can you please fix it? But all in all I really like the library!

[facontidavide]

Honestly, this change makes me a little uncomfortable because of the poor performance of std::istringstream-

In a perfect world, I would like to use this, https://en.cppreference.com/w/cpp/utility/from_chars

But it is c++17 :(

Using this would be a solution https://abseil.io/about/design/charconv
But despite my love for Abseil, I don't want to add this dependency....

[moritzknaust]

I'm not really an expert in C++ development, so I think I cannot help you much at this point. I only found the error and this was the first solution I found...

[facontidavide]

I will try to figure out a solution. Thanks for reporting the issue

[facontidavide]

I found a solution that is faster. Fixed.

http://quick-bench.com/DWaXRWnxtxvwIMvZy2DxVPEKJnE