call execute with macro as an argument

[SAS_inquisitive]

Hello,

In the following code, can we say macro %datasets is enclosed in single quotes or three parts  ie. '%datasets(name= ', strip(name), and  ');'  are concatenated by ||.  Which one is correct? 

data _null_;

     set sashelp.class;

     call execute('%datasets(name='||strip(name)||');');

run;

Below example is taken from Carpenter's macro book where author has mentioned "Because the %PRTDSN is enclosed in single quotes, the text is not seen as macro reference when data step is compiled".

data  _null_;

   set macro3.dbdir;

   call execute ('%prtdsn(dsn='||dsn||')');

run;

Thanks !

[Reeza]

If it's not in double quotes SAS sees it as a string. The code above generates a string that is passed to call execute. In this case that string ends up resolving to a macro call but it certainly doesn't have to. 

[SAS_inquisitive]

@Reeza  For me, it is easier to understand as three strings concatenated by || as the argument of the call execute has to be string. But I might be misunderstanding it.

[Reeza]

That's correct, but String + string = String 

😄

[Astounding]

You can use whatever wording you are comfortable with, but the process is this.  The DATA step puts together all the strings into a single string, before CALL EXECUTE sees it.  CALL EXECUTE sees just one string.  In a way, you can reason this out for yourself if you consider that CALL EXECUTE would not be expected to parse ||.

Also note, while Carpenter's book is correct, the execution phase of the DATA step does recognize the macro call (even if compilation does not).  CALL EXECUTE will execute macro language statements as soon as possible, without necessarily waiting for the current DATA step to finish.  It is a very tricky issue.

[PGStats]

Simplify your code by being more explicit :

data _null_;
    set sashelp.class;
    macroCall = cats('%datasets(name=', name, ');');
    put macroCall= ; /* for debug */
    call execute(macroCall);
run;

[Tom · Accepted solution]

When SAS is parsing the code the character string %DATASETS does NOT trigger a macro call because it is enclosed in single quotes.  When the data step is running this code snippet 

'%datasets(name='||strip(name)||');'

will generate the charater strings like:

%datasets(name=Alfred);

Which will be passed to CALL EXECUTE. to be parsed. Since SAS can now see the %DATASETS it will run the macro and store the generated code into the execution stack to run AFTER the data step stops.  You can tell because the lines in the SAS log that begin with + that show the code that CALL EXECUTE generated you will see the actual code the macro generates but you will NOT see the macro call itself. This can cause timing issue, especially if the macro code generates and uses macro variables.

You can fix this by using the %NRSTR() macro quoting function in your original data step code like this:

'%nrstr(%datasets)(name='||strip(name)||');'

To see the difference try runing this simple example.

%macro datasets(name); %unquote(* NAME = &name ;) %mend datasets;
data _null_;
  set sashelp.class (obs=2);
  call execute('%datasets(name='||strip(name)||');');
  call execute('%nrstr(%datasets)(name='||strip(name)||');');
run;

 Results:

1    + * NAME = Alfred ;;
2    + %datasets(name=Alfred);
3    + * NAME = Alice ;;
4    + %datasets(name=Alice);