Using SAS/IML Software to Generate IML Statements

Executing a String Immediately

The PUSH, QUEUE, and EXECUTE commands are especially useful when used in conjunction with the pause and resume features because they enable you to generate a pause-interrupt command to execute the code you push and return from it via a pushed RESUME statement. In fact, this is precisely how the EXECUTE subroutine is implemented generally.

CAUTION: Note that the push and resume features work this way only in the context of being inside modules. You cannot resume an interrupted sequence of statements in immediate mode - that is, not inside a module.

For example, suppose that you collect program statements in a matrix called CODE. You push the code to the command input stream along with a RESUME statement and then execute a PAUSE statement. The PAUSE statement interrupts the execution, parses and executes the pushed code, and returns to the original execution via the RESUME statement. Here is the code:

  
    proc iml; 
    start testpush; 
       print '*** ENTERING MODULE TESTPUSH ***'; 
       print '*** I should be 1,2,3: '; 
       /* constructed code * / 
       code = ' do i = 1 to 3; print i; end;   '; 
       /* push code+resume */ 
       call push (code, 'resume;'); 
       /* pause interrupt  */ 
       pause; 
       print '*** EXITING MODULE TESTPUSH ***'; 
    finish;
 

When the PAUSE statement interrupts the program, the IML procedure then parses and executes the following line:

  
    do i=1 to 3; print i; end; resume;
 

The RESUME command then causes the IML procedure to resume the module that issued the PAUSE.

Note: The EXECUTE routine is equivalent to a PUSH command, but it also adds the push of a RESUME command, then issues a pause automatically.

A CALL EXECUTE command should be used only from inside a module because pause and resume features do not support returning to a sequence of statements in immediate mode.