How to write macro that creates global variable from another global variable and macro parameter

Question

I have global variable &project_path and need to write macro %set_path that will create another global variable which is equal &project_path\parameter. In my case name of new variable have to be parameter_path. I am new in SAS macro and as I understand they can't return values ​​like normal functions, so I can't do something like log_path=%set_path(log)? So I have to pass a new variable as a parameter like %set_path(log_path, log) but then I can't make log_path Global? How to solve this problem?

The thing I came up with is to set the name of the new variable depending on the parameter. But, it only works if you add a prefix. I need a postfix. And anyway, in general, it looks like not the best option

%macro set_path(sub_dir);
    %global &sub_dirSet;
    %let &sub_dirSet = &project_path\&sub_dir;
%mend set_path;

%set_path(data);
%set_path(log);

%put &dataSet;
%put &logSet;

Of course I tried something like

%macro set_path(var_name, sub_dir);
    %global var_name;
    %let var_name = &project_path\&sub_dir;
%macro set_path;

but as I understand it is fundamentally wrong

Answer 1

As a general coding pattern, it's usually a good idea to avoid creating lots of global macro variables. But to your question of how to add a postfix, you can use a . to end a macro variable reference and add a postfix. So I think your approach would work with:

%let project_path=\\my\dir ;

%macro set_path(sub_dir);
    %global &sub_dir.Set;
    %let &sub_dir.Set = &project_path\&sub_dir;
%mend set_path;

%set_path(data)
%set_path(log)

%put &dataSet;
%put &logSet;