Special Cases of Scope with the CALL SYMPUT Routine :: SAS(R) 9.3 Macro Language: Reference

Overview of CALL SYMPUT Routine

Most problems with CALL SYMPUT involve the lack of a precise step boundary between the CALL SYMPUT statement that creates the macro variable and the macro variable reference that uses that variable. (For more information, see CALL SYMPUT Routine.) However, a few special cases exist that involve the scope of a macro variable created by CALL SYMPUT. These cases are good examples of why you should always assign a scope to a variable before assigning a value rather than relying on SAS to do it for you.

Two rules control where CALL SYMPUT creates its variables:

CALL SYMPUT creates the macro variable in the current symbol table available while the DATA step is executing, provided that symbol table is not empty. If it is empty (contains no local macro variables), usually CALL SYMPUT creates the variable in the closest nonempty symbol table.
However, there are three cases where CALL SYMPUT creates the variable in the local symbol table, even if that symbol table is empty:
- Beginning with SAS Version 8, if CALL SYMPUT is used after a PROC SQL, the variable will be created in a local symbol table.
- If the macro variable SYSPBUFF is created at macro invocation time, the variable will be created in the local symbol table.
- If the executing macro contains a computed %GOTO statement, the variable will be created in the local symbol table. A computed %GOTO statement is one that uses a label that contains an & or a % in it. That is, a computed %GOTO statement contains a macro variable reference or a macro call that produces a text expression. Here is an example of a computed %GOTO statement:
  
  %goto &home;

The symbol table that is currently available to a DATA step is the one that exists when SAS determines that the step is complete. (SAS considers a DATA step to be complete when it encounters a RUN statement, a semicolon after data lines, or the beginning of another step.)

In simplest terms, if an executing macro contains a computed %GOTO statement, or if the macro variable SYSPBUFF is created at macro invocation time, but the local symbol table is empty, CALL SYMPUT behaves as if the local symbol table was not empty, and creates a local macro variable.

You might find it helpful to use the %PUT statement with the _USER_ option to determine what symbol table the CALL SYMPUT routine has created the variable in.

Example Using CALL SYMPUT with Complete DATA Step and a Nonempty Local Symbol Table

Consider the following example, which contains a complete DATA step with a CALL SYMPUT statement inside a macro:

%macro env1(param1);
   data _null_;
      x = 'a token';
      call symput('myvar1',x);
   run;
%mend env1;

%env1(10)

data temp;
   y = "&myvar1";
run;

When you submit these statements, you receive an error message:

WARNING:   Apparent symbolic reference MYVAR1 not resolved.

This message appears because the DATA step is complete within the environment of ENV1 (that is, the RUN statement is within the macro) and because the local symbol table of ENV1 is not empty (it contains parameter PARAM1). Therefore, the CALL SYMPUT routine creates MYVAR1 as a local variable for ENV1, and the value is not available to the subsequent DATA step, which expects a global macro variable.

To see the scopes, add a %PUT statement with the _USER_ option to the macro, and a similar statement in open code. Now invoke the macro as before:

%macro env1(param1);
   data _null_;
      x = 'a token';
      call symput('myvar1',x);
   run;

   %put ** Inside the macro: **;
   %put _user_;
%mend env1;

%env1(10)

%put ** In open code: **;
%put _user_;

data temp;
   y = "&myvar1";  /* ERROR - MYVAR1 is not available in open code. */
run;

When the %PUT _USER_ statements execute, they write the following information to the SAS log:

** Inside the macro: **
ENV1    MYVAR1    a token
ENV1    PARAM1    10

** In open code: **

The MYVAR1 macro variable is created by CALL SYMPUT in the local ENV1 symbol table. The %PUT _USER_ statement in open code writes nothing to the SAS log, because no global macro variables are created.

The following figure shows all of the symbol tables in this example.

The Symbol Tables with the CALL SYMPUT Routine Generating a Complete DATA Step

The CALL SYMPUT Routine in a Macro Generating a Complete DATA Step

Example Using CALL SYMPUT with an Incomplete DATA Step

In the macro ENV2, shown here, the DATA step is not complete within the macro because there is no RUN statement:

%macro env2(param2);
   data _null_;
      x = 'a token';
      call symput('myvar2',x);
%mend env2;

%env2(20)
run;

data temp;
   y="&myvar2";
run;

These statements execute without errors. The DATA step is complete only when SAS encounters the RUN statement (in this case, in open code). Thus, the current scope of the DATA step is the global scope. CALL SYMPUT creates MYVAR2 as a global macro variable, and the value is available to the subsequent DATA step.

Again, use the %PUT statement with the _USER_ option to illustrate the scopes:

%macro env2(param2);
   data _null_;
      x = 'a token';
      call symput('myvar2',x);

   %put ** Inside the macro: **;
   %put _user_;
%mend env2;

%env2(20)

run;

%put ** In open code: **;
%put _user_;

data temp;
   y="&myvar2";
run;

When the %PUT _USER_ statement within ENV2 executes, it writes the following to the SAS log:

** Inside the macro: **
ENV2   PARAM2   20

The %PUT _USER_ statement in open code writes the following to the SAS log:

** In open code: **
GLOBAL   MYVAR2   a token

The following figure shows all the scopes in this example.

The Symbol Tables with the CALL SYMPUT Routine Generating an Incomplete DATA Step

The CALL SYMPUT Routine in a Macro Generating an Incomplete DATA Step

Example Using CALL SYMPUT with a Complete DATA Step and an Empty Local Symbol Table

In the following example, ENV3 does not use macro parameters. Therefore, its local symbol table is empty:

%macro env3;
   data _null_;
      x = 'a token';
      call symput('myvar3',x);
   run;

   %put ** Inside the macro: **;
   %put _user_;
%mend env3;

%env3

%put ** In open code: **;
%put _user_;

data temp;
   y="&myvar3";
run;

In this case, the DATA step is complete and executes within the macro, but the local symbol table is empty. So, CALL SYMPUT creates MYVAR3 in the closest available nonempty symbol table—the global symbol table. Both %PUT statements show that MYVAR3 exists in the global symbol table:

** Inside the macro: **
GLOBAL    MYVAR3   a token

** In open code: **
GLOBAL    MYVAR3   a token

Example Using CALL SYMPUT with SYSPBUFF and an Empty Local Symbol Table

In the following example, the presence of the SYSPBUFF automatic macro variable causes CALL SYMPUT to behave as if the local symbol table were not empty, even though the macro ENV4 has no parameters or local macro variables:

%macro env4 /parmbuff;
 data _null_;
      x = 'a token';
      call symput('myvar4',x);
   run;

   %put ** Inside the macro: **;
   %put _user_;
   %put &syspbuff;
%mend env4;

%env4

%put ** In open code: **;
%put _user_;
%put &syspbuff;

data temp;
   y="&myvar4";  /* ERROR - MYVAR4 is not available in open code */
run;

The presence of the /PARMBUFF specification causes the SYSPBUFF automatic macro variable to be created. So, when you call macro ENV4, CALL SYMPUT creates the macro variable MYVAR4 in the local symbol table (that is, in ENV4's), even though the macro ENV4 has no parameters and no local variables.

The results of the %PUT statements prove this—the score of MYVAR4 is listed as ENV4, and the reference to SYSPBUFF does not resolve in the open code %PUT statement because SYSPBUFF is local to ENV4:

** Inside the macro: **
b ENV4     MYVAR4    a token

** In open code: **
WARNING: Apparent symbolic reference SYSPBUFF not resolved.

For more information, see SYSPBUFF Automatic Macro Variable.