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XTRAN Demonstration:  Highlight File & Terminal I/O Code in PL/I

The following example used an XTRAN rules file comprising 166 non-comment lines of "meta-code" (XTRAN's rules language) to highlight PL/I code involved with either file or terminal I/O, rendering the code as HTML for coloring.  The rules took about four hours to create and debug.  They are not particularly specific to PL/I; they can easily be adapted to do the same for any 3GL language.

Note that the rules infer file or terminal I/O usage of a variable to which a value is assigned that contains any variables of either type.

The following is an English paraphrase of the XTRAN rules used for this example:

        Specify HTML as module rendering "decoration" prefix and suffix
        Specify HTML as statement rendering "decoration" prefix and suffix,
          according to statement's I/O involvement if any
        Specify HTML as expression rendering "decoration" prefix and suffix,
          according to expression's I/O involvement if any
        For each PL/I statement
            If DISPLAY or ACCEPT statement
                Mark statement as "terminal I/O"
                Mark all variables in statement as "terminal I/O"
            Else if CLOSE, OPEN, READ, or WRITE statement
                Mark statement as "file I/O"
                Mark all variables in statement as "file I/O"
        While variables to mark
            For each PL/I statement
                If assignment statement
                    If right side has "file I/O" and/or "terminal I/O" variables
                        If left side not already marked
                            Mark left side as such
        Render code; XTRAN will decorate it as specified       

The input to and output from XTRAN are untouched.

 Input to XTRAN:

prc:    PROC (dspio1, filio1);
        DCL (dspio1, dspio2) FIXED BIN (31);
        DCL (filio1, filio2, filio3) FIXED BIN (31);
        DCL (bthio1, bthio2) FIXED BIN (31);
        DCL (neither1, neither2) FIXED BIN (31);
        DCL file1 FILE;

        DISPLAY ('First argument is ' || dspio1);
        dspio2 = dspio1;
        OPEN FILE(file1) INPUT TITLE('foo');
        READ FILE(file1) INTO(filio1);
        filio2 = filio1 + 1;
        bthio1 = bthio1 + filio1;
        neither1 = 1;
        neither2 = neither1 + 1;
        IF (filio2 > filio3) THEN
            filio3 = filio2;
        bthio1 = dspio1;
        bthio2 = filio1 + bthio1;
        dspio1 = neither2;
        CLOSE FILE(file1);
        RETURN;
        END prc;

 Output from XTRAN (HTML):

PL/I with File and Terminal I/O Highlighted

• File I/O
• Terminal I/O
• Both kinds of I/O
• Neither kind of I/O

prc:    PROCEDURE (dspio1, filio1);
        DCL (dspio1, dspio2) FIXED BIN (31);
        DCL (filio1, filio2, filio3) FIXED BIN (31);
        DCL (bthio1, bthio2) FIXED BIN (31);
        DCL (neither1, neither2) FIXED BIN (31);
        DCL file1 FILE;

        DISPLAY ('First argument is ' || dspio1);
        dspio2 = dspio1;
        OPEN FILE(file1) INPUT TITLE('foo');
        READ FILE(file1) INTO(filio1);
        filio2 = filio1 + 1;
        bthio1 = bthio1 + filio1;
        neither1 = 1;
        neither2 = neither1 + 1;
        IF filio2 > filio3
          THEN
            filio3 = filio2;
        bthio1 = dspio1;
        bthio2 = filio1 +
          bthio1;
        dspio1 = neither2;
        CLOSE FILE(file1);
        RETURN;
        END prc;

COPYRIGHT 2012; reproduction prohibited without permission.  Revised 2009-09-11

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