While in the ada main directory, using Python 3, type:
python singleheader/amalgamate.py
This will create two new files (ada.h and ada.cpp).
You can then compile the demo file as follows:
c++ -std=c++20 -c demo.cpp
It will produce a binary file (e.g., demo.o) which contains ada.cpp.
c++ -std=c++20 -o demo demo.cpp
./demo
You may build and link using CMake (--target demo), because CMake can configure all the necessary flags.
You may also build a C executable.
c++ -c ada.cpp -std=c++20
cc -c demo.c
c++ demo.o ada.o -o cdemo
./cdemo