Select from the first to the k-th element in a macro list variable

[AndreMenezes]

Dear all,

Suppose that I have the following macro list variable:

%let list = a1, a2, a3, a4, a5;

If I want to create another macro variable selecting the elements a1, a2 and a3 how can I do this?

Thanks.

AFM.

[Astounding]

You really turned this into a difficult problem by inserting commas into your list.  Is there any chance you can go back and change the code so that you get:

%let list = a1 a2 a3 a4 a5;

[ChrisBrooks]

I agree with @Astounding it's easier without the commas - then check out the %scan macro function which allows you to select the nth element from the list, put that inside a %do loop and you're done....

[Astounding · Accepted solution]

If you need to keep the commas, here's a trick that might work.  (I can't test it at the moment so that part is up to you).

%let list = a1, a2, a3, a4, a5;

%macro first3;

   %global newmacrovar;

   %let newmacrovar=;

   %local k;

   %do k=1 %to 3;

      %let newmacrovar = &newmacrovar %scan("&list", &k, ", ");

   %end;

%mend first3;

I'm omitting the commas from the new macro variable, but they can be added with a single additional line of code:

   %do k=1 %to 3;

      %let newmacrovar = &newmacrovar %scan("&list", &k, ", ");

      %if &k < 3 %then %let newmacrovar = &newmacrovar,;

   %end;

[AndreMenezes]

I appreciate your solution.
I solved the problem using the %do loop, but I thought there were some function like scan that select the k-th element from a list macro variable.

[Ksharp]

%let list = a1, a2, a3, a4, a5;
%let want=%sysfunc(prxchange(s/\W+\w+\W+\w+$//,1,%nrbquote(&list)));

%put &want ;

[AndreMenezes]

Thank you very much for your answer!