How to understand "#data_array" in std::string?

[beizhengren]

Description

Hi, thanks for your terrific work.
During I add a test for vector, I find #data_array, as following.
I have never seen the programmer in c++. How should I understand it?

out.push_back(std::string(#data_array "[") + std::to_string(out.size() + 1) + "]"); \

the original link: https://github.com/onqtam/doctest/blob/master/doc/markdown/parameterized-tests.md
Thanks!

[onqtam]

Hi @beizhengren , If I understand you correctly, you are wondering what #data_array does exactly - that's a preprocessor operator and it turns whatever is passed to the macro into a C string literal. So for example:

    int data;
    std::list<int> my_real_data_array = {1, 2, 3, 4};
    DOCTEST_VALUE_PARAMETERIZED_DATA(data, my_real_data_array);

in this case there will be 4 subcases generated which will be named my_real_data_array[<index>].

Have a look at these links:

• https://stackoverflow.com/questions/10507264/how-to-use-macro-argument-as-string-literal
• https://en.cppreference.com/w/cpp/preprocessor/replace#.23_and_.23.23_operators
• https://gcc.gnu.org/onlinedocs/gcc-8.4.0/cpp/Stringizing.html

Let me know if this helps :)

[beizhengren]

Hi @onqtam
Thank you so much for your quick and clear reply!
It's my first time to know replacing text macros.
It help me a a lot！^ ^