topic Re: %macro positional parameter in SAS Programming

%macro positional parameter

chouchou — Sat, 16 Aug 2014 21:08:54 GMT

%macro location(type);

data _null_;

call symput('type','Train');

run;

%mend;

%put &type;

%location(Automobile)

%put &type;

Two similar warnings come out:WARNING: Apparent symbolic reference TYPE not resolved.

I think the first %put &type; should resolve to Train; the second %put &type; should resolve to Automobile.

Could anyone explain to me why I am totally wrong? Thank you guys.

Re: %macro positional parameter

data_null__ — Sat, 16 Aug 2014 21:33:35 GMT

Maybe this is what you are trying to do. But it doesn't seen to have a point.

%macro location(type); 
   data _null_;
      call symputx('type',"&type",'G');
      run;
   %mend; 
%location(Auto);
%put NOTE: &=type;

Re: %macro positional parameter

Quentin — Sun, 17 Aug 2014 01:14:15 GMT

It's all about scoping rules.

Macro variables are stored in symbol tables. There is a global symbol table (used for the whole SAS session), and a macro can create a local symbol table which exists while the macro is executing.

Your macro creates a local symbol table to hold the parameter (macro variable) TYPE. When CALL SYMPUT executes and writes the value TRAIN to a macro variable TYPE, it needs to decide whether to write it to the local macro variable that exists named TYPE, or to the global symbol table. The scoping rules CALL SYMPUT follows tell it to write the the macro variable TYPE in the local symbol table.

Your %PUT statements outside of the macro don't resolve, because they are looking for a macro variable named TYPE in the global symbol table. And there isn't one.

data_null_'s solution explicitly tells SYMPUTX to write the macro variable TYPE to the global symbol table, accomplishing your apparent purpose.

--Q.