You can get all the functions this way:
clone the stan-docs repo then cd into it run the python script with the major and minor version numbers:
python3 extract_function_sigs.py 2 28
then run a bash command to extract only the unique names
cut -d ';' -f1 stan-functions-2_28.txt | uniq -u > stan_functions_list-2_28.txt
stan_functions_list-2_28.txt (6.4 KB)
The output of the python script has all the valid signatures as well. I just needed the names.