Attributes for DO statements

The following attributes give a quick access to the most useful parts of DO statements. They must be applied to a AST of variant "do".

  $\blacktriangleright$ stat.BOUND

 
The   expression returns the whole control structure of the DO statement stat. Its variant is "bounds" for an indexed DO statement (i.e. something like 'DO I=1,n ...'), "while" for a DO WHILE statement and "none" for an infinite DO.
$\vartriangleright$ Example 44:How to differentiate DO statements

    IF (stat.VARIANT=="do") THEN 
      IF (stat.BOUND.VARIANT=="bounds") THEN 
        PRINT "I am an indexed DO loop" 
      ELSEIF (stat.BOUND.VARIANT=="while") THEN 
        PRINT "I am a DO WHILE loop" 
      ELSEIF (stat.BOUND.VARIANT=="none") THEN 
        PRINT "I am an infinite DO loop" 
      ELSE 
        PRINT "I don't know who I am." 
      ENDIF
    ENDIF

  $\vartriangleright$ Remark: stat.BOUND is equivalent to stat.CHILD(3)

  $\blacktriangleright$ stat.INDEX

 
The   expression returns the variable index of the indexed DO statement stat. This is a shortcut to stat.CHILD(3).CHILD(1)

  $\blacktriangleright$ stat.START

 
The   expression returns the start value of the indexed DO statement stat. This is a shortcut to stat.CHILD(3).CHILD(2)

  $\blacktriangleright$ stat.END

 
The   expression returns the start value of the indexed DO statement stat. This is a shortcut to stat.CHILD(3).CHILD(3)

  $\blacktriangleright$ stat.STEP

 
The   expression returns the start value of the indexed DO statement stat. The step variant is "none" when the step is implicit. This is a shortcut to stat.CHILD(3).CHILD(4)

  $\blacktriangleright$ stat.BODY

 
The   expression returns the body of the DO statement stat. This is a shortcut to stat.CHILD(4)

  $\blacktriangleright$ stat.LABEL

 
The   expression returns the label associated to the DO statement stat (i.e. the label before the index variable). If there is no label (the statement is ended by ENDDO) then the attribute returns a node of variant "none".

$\vartriangleright$ Example 45:A simple inversion of the step sign        

  SCRIPT SignInvert ()
    loop := $cstat 
    IF (loop.VARIANT == "do") THEN
      IF (loop.BOUND.VARIANT == "bounds") THEN
         // Exchange the start and the step 
         start := loop.START 
         loop.START <-  loop.END
         loop.END <-  start
         // Invert the condition 
         step := loop.STEP
         IF (step.VARIANT=="none" )THEN
            step := PARSEEXPR("-1") 
         ELSE
            step := PARSEEXPR("-(%e)",step) 
         ENDIF
         loop.STEP <- step 
      ENDIF
    ENDIF
  ENDSCRIPT